[ { "id": "authors:dygxp-j1g12", "collection": "authors", "collection_id": "dygxp-j1g12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111109-140327494", "type": "book_section", "title": "Developing Cross Section Sets for Fluorocarbon Etchants", "book_title": "Atomic and Molecular Data and Their Applications", "author": [ { "family_name": "Winstead", "given_name": "Carl", "clpid": "Winstead-C" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Schultz", "given_name": "D. R.", "clpid": "Schultz-D-R" }, { "family_name": "Krsti\u0107", "given_name": "P. S.", "clpid": "Krsti\u0107-P-S" }, { "family_name": "Ownby", "given_name": "F.", "clpid": "Ownby-F" } ], "abstract": "Successful modeling of plasmas used in materials processing depends on knowledge of a variety of collision cross sections and reaction rates, both within the plasma and at the surface. Electron-molecule collision cross sections are especially important, affecting both electron transport and the generation of reactive fragments by dissociation and ionization. Because the supply of cross section data is small and measurements are difficult, computational approaches may make a valuable contribution, provided they can cope with the significant challenges posed. In particular, a computational method must deal with the full complexity of low-energy electron-molecule interactions, must treat polyatomic molecules, and must be capable of computing cross sections for electronic excitation. These requirements imply that the method will be numerically intensive and thus must exploit high-performance computers to be practical. We have developed an ab initio computational method, the Schwinger multichannel (SMC) method, that possesses the characteristics just described, and we have applied it to compute cross sections for a variety of molecules, with particular emphasis on fluorocarbon and hydrofluorocarbon etchants used in the semiconductor industry. A key aspect of this work has been an awareness that cross section sets, validated when possible against swarm data, are more useful than individual cross sections. To develop such sets, cross section calculations must be integrated within a focused collaborative effort. Here we describe electron cross section calculations carried out within the context of such a focused effort, with emphasis on fluorinated hydrocarbons including CHF3 (trifluoromethane), c-C_(4)F_(8) (octafluorocyclobutane), and C_(2)F_(4) (tetrafluoroethene).", "doi": "10.1063/1.1516341", "isbn": "0-7354-0091-1", "publisher": "American Institute of Physics", "place_of_publication": "Melville, NY", "publication_date": "2002-10-21", "pages": "241-250" }, { "id": "authors:dsswc-j3c53", "collection": "authors", "collection_id": "dsswc-j3c53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151027-154127445", "type": "book_section", "title": "Energy- and Angle-Resolved Femtosecond Photoelectron Spectra from Rotating Molecules", "book_title": "Femtochemistry: With the Noble Lecture of A. Zewail", "author": [ { "family_name": "Arasaki", "given_name": "Yasuki", "clpid": "Arasaki-Yasuki" }, { "family_name": "Takatsuka", "given_name": "Kazuo", "clpid": "Takatsuka-Kazuo" }, { "family_name": "Wang", "given_name": "Kwanghsi", "clpid": "Wang-Kwanghsi" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "De Schryver", "given_name": "Frans C.", "clpid": "De-Schryver-F-C" }, { "family_name": "De Feyter", "given_name": "Steven", "clpid": "De-Feyter-S" }, { "family_name": "Schweitzer", "given_name": "Gerd", "clpid": "Schweitzer-G" } ], "abstract": "We have extended our formulation of energy- and angle-dependent pump-probe photoelectron spectroscopy for vibrational wavepackets to account for the effects of molecular rotation. We employ a classical model for rotation, which should be applicable to many cases of interest, and present some results of applications to photoelectron spectra for wavepackets on the double-minimum state of Na_2. The results provide useful insights into such time-resolved photoelectron spectra and suggest strategies for deconvolution of the vibrational and rotational content of the photoelectron signals.", "doi": "10.1002/3527600183.ch16", "isbn": "9783527302598", "publisher": "Wiley", "place_of_publication": "New York, NY", "publication_date": "2001-10-08", "pages": "281-293" }, { "id": "authors:69381-pqh09", "collection": "authors", "collection_id": "69381-pqh09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151027-154130835", "type": "book_section", "title": "Electron\u2013Molecule Collisions in Low-Temperature Plasmas: The Role of Theory", "book_title": "Fundamentals of Plasma Chemistry", "author": [ { "family_name": "Winstead", "given_name": "Carl", "clpid": "Winstead-C" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Bederson", "given_name": "Benjamin", "clpid": "Bederson-B" }, { "family_name": "Walther", "given_name": "Herbert", "clpid": "Walther-H" } ], "abstract": "This chapter discusses the contribution that theoretical methods can make to a knowledge of electron-molecule collision behavior, and thereby to an understanding of low-temperature plasmas. Its aim is to survey both the relevant problems and the methods that have been developed to treat those problems. Without delving deeply into the workings of any specific method, we will try to convey both the capabilities and the limitations of present theoretical approaches, and to point out directions for future progress. \n\nIf one hopes to develop detailed, predictive models of plasmas, microscopic information such as electron-molecule collision probabilities clearly is needed. But why obtain that information from theory? The short answer is that experimental data are often absent and-given the difficulty of the measurements and the paucity of research groups conducting them-in many cases are likely to remain so indefinitely. A longer answer would add that, as both theoretical methods and computer hardware improve, theory is, at least in some areas, becoming competitive with experiment in terms of accuracy and time to solution. \n\nTo set the stage for the subsequent discussion, let us briefly recall some features of the electron-molecule collision problem as it arises in low-temperature, nonequilibrium plasmas. Most salient is that the electron kinetic energies are low, with the energy distribution often peaking at a few e V Thus electrons in the higher-energy tail of the distribution may be responsible for important inelastic processes, such as electronic excitation and ionization of molecules, whose thresholds often lie above 10 e V, but very little of the plasma chemistry will be driven by truly high-energy electrons-that is, electrons whose energies greatly exceed the average kinetic energies of molecular valence electrons. This simple fact has profound consequences for both theory and experiment, because in both instances it is far more difficult to work with low-energy electrons. In the case of theory, many simplifying approximations that can be applied at high energy are excluded, and it becomes necessary to employ a many-body approach that treats the projectile electron and the electrons belonging to the molecule on an equal footing, with a proper accounting being made for the indistinguishability of electrons. \n\nAs we will see later, the low-energy electron-molecule collision problem is far from hopeless; certain simplifications can usually be made without seriously\nimpairing accuracy. What remains to be solved, however, is still formidable-a version of Schrodinger's equation for the motion of several (perhaps several dozen) electrons. As this is a second-order partial differential equation with three spatial degrees of freedom per electron, direct integration is completely out of the question. The goal of theory, then, is to develop practical methods of approximation that allow one to extract reliable collision information.", "doi": "10.1016/S1049-250X(08)60123-8", "isbn": "978-0-12-003843-5", "publisher": "Academic Press", "place_of_publication": "San Diego, CA", "publication_date": "2000", "pages": "111-145" }, { "id": "authors:c5hqh-d3345", "collection": "authors", "collection_id": "c5hqh-d3345", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151019-143012192", "type": "book_section", "title": "Core Relaxation Effects in Molecular Photoionization", "book_title": "VUV and Soft X-Ray Photoionization", "author": [ { "family_name": "Schirmer", "given_name": "Jochen", "clpid": "Schirmer-J" }, { "family_name": "Braunstein", "given_name": "Matthew", "clpid": "Braunstein-M" }, { "family_name": "Lee", "given_name": "Mu-Tao", "clpid": "Lee-Mu-Tao" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Becker", "given_name": "Uwe", "clpid": "Becker-U" }, { "family_name": "Shirley", "given_name": "David A.", "clpid": "Shirley-D-A" } ], "abstract": "Ionization of K-shell or, more generally, of deep inner-shell electrons in atoms and molecules is accompanied by a considerable rearrangement of the valence (outer-shell) electrons in response to the reduced shielding of the nuclear attraction.(1) This adjustment of the valence electrons, referred to as electronic relaxation, leads to a significant energy lowering of the final ionic state relative to a state where the valence electron distribution of the initial state is maintained (\"frozen\"). The magnitude of this relaxation energy scales with the number of valence electrons. In the case of the K-shell ionization of second-row atoms (Z = 3\u221210), for example, the relaxation energies (in eV) are approximately given by \u0395 ^R(Z) = 3.1 (Z \u2212 2.2). In a molecular environment the corresponding relaxation energies are typically 2\u22123 eV larger than the values for the free atom. Relaxation not only plays a role in the ionic core but also affects the motion of the outgoing photoelectron. The relaxation of the valence electrons, being essentially a contraction of the valence charge distribution, quite effectively screens the inner-shell hole potential experienced by the photoelectron. This means that the potential of the relaxed ionic core is less attractive than its unrelaxed (frozen) counterpart. As a consequence, resonances in the photoionization cross section will appear at higher energy for a relaxed core than for an unrelaxed (frozen) core. Concomitantly with the shift to higher energy, the resonance peaks will be lowered and broadened as a result of relaxation.", "doi": "10.1007/978-1-4613-0315-2_4", "isbn": "978-1-4613-7993-5", "publisher": "Plenum Press", "place_of_publication": "New York, NY", "publication_date": "1996", "pages": "105-133" }, { "id": "authors:7asbd-x9a27", "collection": "authors", "collection_id": "7asbd-x9a27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151019-143011741", "type": "book_section", "title": "Highly Parallel Computational Techniques for Electron-Molecule Collisions", "book_title": "Advances In Atomic, Molecular, and Optical Physics", "author": [ { "family_name": "Winstead", "given_name": "Carl", "clpid": "Winstead-C" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Bederson", "given_name": "Benjamin", "clpid": "Bederson-B" }, { "family_name": "Walther", "given_name": "Herbert", "clpid": "Walther-H" } ], "abstract": "Though most of the current knowledge of electron\u2013molecule collisions derives from experiments, accurate measurements of collision cross sections are quite difficult, especially for inelastic processes; few groups worldwide have undertaken this challenging work. Demand for cross section data already exceeds supply and the list of \"critical\" but absent data grows longer daily. Moreover, the species of interest include not only stable molecules, but also those radicals and ions whose populations within the plasma may be significant and experiments will be all the more difficult for such transient species. Most recent theoretical studies of electron\u2013molecule collisions have relied on variational approximations to the scattering amplitude or to some closely related quantity, thereby avoiding direct numerical solution of Schrodinger's equation. However, the studies of many-electron systems remain numerically intensive despite the choice of an efficient theoretical approach and the work discussed in the chapter depends on exploiting the prodigious advances in computational power that have resulted from the development of massively parallel processors.", "doi": "10.1016/S1049-250X(08)60210-4", "isbn": "978-0-12-003836-7", "publisher": "Elsevier", "publication_date": "1996", "pages": "183-219" }, { "id": "authors:4k9w3-s3125", "collection": "authors", "collection_id": "4k9w3-s3125", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151120-153304934", "type": "book_section", "title": "Rotationally Resolved Photoelectron Spectra at Near-Threshold Kinetic Energies", "book_title": "High Resolution Laser Photoionization and Photoelectron Studies", "author": [ { "family_name": "Wang", "given_name": "Kwanghsi", "clpid": "Wang-Kwanghsi" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Powis", "given_name": "Ivan", "clpid": "Powis-I" }, { "family_name": "Baer", "given_name": "Tomas", "clpid": "Baer-T" }, { "family_name": "Ng", "given_name": "Cheuk-Yiu", "clpid": "Ng-Cheuk-Yiu" } ], "abstract": "Rotationally resolved photoelectron spectra and their associated photoelectron angular distributions can clearly provide significant insight into the dynamics of molecular photoionization, one of the simplest of molecular fragmentation processes. Such state-resolved spectra are an obvious signature of the exchanges of energy and angular momentum between the photoelectron and molecular ion. With the exception of H2 (Pollard et al., 1982; Anderson et al., 1984; Pratt et al., 1984, 1990; O'Halloran et al. , 1987; McCormack et al., 1990) and D2 (Peatman et al., 1983; O'Halloran et al., 1989; Pratt et al., 1990a) and of higher J levels of diatomic systems such as NO (Wilson et al., 1984; Viswanathan et al., 1986a, l986b; Allendorf et al., 1989), NH (de Beer et al., 1991; Wang et al., 1992) and OH\n(de Beer et al., 1991 b) with their large rotational spacing, rotational resolution in photoelectron spectra has generally been beyond the reach of the techniques of conventional photoelectron spectroscopy. With the recent development of zero kinetic energy (ZEKE) photoelectron spectroscopy based on pulsed field ionization (PFI) of very high Rydberg levels, however, it is now possible to exploit the narrow bandwidth of laser radiation to achieve sub-wavenumber resolution in ion rovibronic state distributions (Sander et al. , 1987; Reiser et al., 1988; Tonkyn et al., 1989; Grant and White, 1991; Muller-Dethlefs and Schlag, 1991). The unprecedented resolution of this technique makes it a powerful tool for investigating the dynamics of near-threshold photoionization and has led to a surge of experimental activity in molecular photoelectron spectroscopy. Furthermore, laser-induced fluorescence\n(LIF) studies can provide even higher resolution than energy-resolved photoelectron measurements and may allow monitoring of the populations of A components of ion\nrotational levels (Xie and Zare, 1989, and personal communication). Rotationally resolved measurements have revealed such interesting spectral features as the\ndependence of photoelectron angular distributions on rotational levels (Anderson et al., 1984; Allendorf et al., 1989), rotational propensity rules (Viswanathan et al. ,\n1986a, 1986b; Sander et al., 1987; Allendorf et al., 1989; Xie and Zare, 1989), parity selectivity in transitions involving electronically degenerate states (Pratt et al.,\n1984; Viswanathan et al. , 1986a; O'Halloran et al. , 1987; Fujii et al., 1988; Xie and Zare, 1989), autoionization (Pratt et al. , 1990a, 1990b; Wiedmann et al., 199 1),\neffects of alignment (McCormack et al., 1990), and the influence of Cooper minima (de Beer et al., 199la, 199lb; Wang et al., 1992) and shape resonances (Braunstein\net al. , 1990) on ion distributions. The underlying dynamics of such rotationally resolved photoelectron spectra can clearly be expected to present new theoretical\nchallenges.", "isbn": "978-0471941583", "publisher": "John Wiley & Sons", "place_of_publication": "New York, NY", "publication_date": "1995-07", "pages": "281-329" }, { "id": "authors:3r94h-fkh42", "collection": "authors", "collection_id": "3r94h-fkh42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151123-094423742", "type": "book_section", "title": "Studies of Electron-Molecule Collisions on Massively Parallel Computers", "book_title": "Modern Electronic Structure Theory", "author": [ { "family_name": "Winstead", "given_name": "Carl", "clpid": "Winstead-C" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Yarkony", "given_name": "David R.", "clpid": "Yarkony-D-R" } ], "abstract": "Electron- molecule collisions occur in a wide variety of contexts. The essential ingredients are physical conditions that permit the presence of molecules - which have dissociation energies on the order of a few electron volts or eV (1 eV = 11,600 K) - and that simultaneously permit the presence of free electrons. If these electrons are produced by ionization of neutral matter, their generation requires on the order of 5-15 eV of energy, enough to dissociate most molecules. Thus systems in which electron- molecule collisions are important are generally far from thermal equilibrium.", "doi": "10.1142/9789812832115_0011", "isbn": "9810229887", "publisher": "World Scientific Publishing", "place_of_publication": "River Edge, NJ", "publication_date": "1995", "pages": "1375-1462" }, { "id": "authors:13qw0-bqa07", "collection": "authors", "collection_id": "13qw0-bqa07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151123-072148061", "type": "book_section", "title": "Studies of Electron-Molecule Collisions on Massively Parallel Computers", "book_title": "High Performance Computing and its Applications in the Physical Sciences", "author": [ { "family_name": "Winstead", "given_name": "Carl", "clpid": "Winstead-C" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Browne", "given_name": "Dana A.", "clpid": "Browne-D-A" } ], "abstract": "Electron-molecule collisions, particularly those leading to dissociation of molecules and hence to production of chemically reactive fragments, play an important role in the modelling of plasmas used in materials processing.\nThe available data base of the cross sections needed in modelling such plasmas is quite fragmentary. In fact, the lack of an adequate data base of relevant cross sections for calculating plasma properties is one of the major\nobstacles to improved modelling and simulation of plasma processes. In this presentation we review the progress we have made in exploiting the high-performance computing provided by the Intel Delta System to obtain\nquantitatively useful estimates of these electron impact cross sections.", "isbn": "9789810217402", "publisher": "World Scientific", "place_of_publication": "Singapore", "publication_date": "1993-09", "pages": "154-175" }, { "id": "authors:e3x15-v6c68", "collection": "authors", "collection_id": "e3x15-v6c68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151028-114740305", "type": "book_section", "title": "Ion rotational distributions for nonlinear molecules at near-threshold photoelectron energies", "book_title": "Laser Techniques for State-Selected and State-to-State Chemistry", "author": [ { "family_name": "Wang", "given_name": "Kwanghsi", "clpid": "Wang-Kwanghsi" }, { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Ng", "given_name": "Cheuk Yiu", "clpid": "Ng-Cheuk-Yiu" } ], "abstract": "Rotationally resolved photoelectron spectra can provide significant insight into the underlying dynamics of molecular photoionization. Recent advances in experimental techniques now make it possible to readily achieve rotational resolution in molecular photoelectron spectra. Here we discuss results of our recent theoretical studies of rotationally resolved photoelectron spectra at near-threshold energies for the nonlinear molecules H_2O, H_2S, and CH_2O (formaldehyde). These studies serve to reveal the rich dynamics of molecular photoionization and, where possible, to provide a robust description of key spectral features of interest in related experimental studies.", "doi": "10.1117/12.143089", "isbn": "9780819410856", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "1993-04-22", "pages": "226-237" }, { "id": "authors:0pc34-xam02", "collection": "authors", "collection_id": "0pc34-xam02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151124-095738953", "type": "book_section", "title": "Ion Rotational Distributions at Near-Threshold Photoelectron Energies", "book_title": "Vacuum Ultraviolet Radiation Physics", "author": [ { "family_name": "Wang", "given_name": "K.", "clpid": "Wang-K" }, { "family_name": "Stephens", "given_name": "J.", "clpid": "Stephens-J" }, { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Wuilleumier", "given_name": "Francois J.", "clpid": "Wuilleumier-F-J" }, { "family_name": "Petroff", "given_name": "Yves", "clpid": "Petroff-Y" }, { "family_name": "Nenner", "given_name": "Ir\u00e8ne", "clpid": "Nenner-I" } ], "abstract": "Rotationally resolved photoelectron spectra can provide significant insight into the underlying dynamics of molecular photoionization. Recent advances in experimental techniques now make it possible to readily achieve rotational resolution in molecular photoelectron spectra. Here we present results of theoretical studies of rotationally resolved photoelectron spectra at low and very near-threshold energies for molecules such aa HBr, NH, NO,\nand CO. These studies serve to reveal the rich dynamics of quantum.state specific studies of molecular photoionization and, where poesible, to provide a robust description of key\nspectral features of interest in related experimental studies.", "isbn": "9789810212520", "publisher": "World Scientific", "publication_date": "1993", "pages": "247-256" }, { "id": "authors:53rah-b8432", "collection": "authors", "collection_id": "53rah-b8432", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151028-114733940", "type": "book_section", "title": "Studies of resonance enhanced multiphoton ionization of molecules", "book_title": "Half collision resonance phenomena in molecules", "author": [ { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Garc\u00eda-Sucre", "given_name": "M\u00e1ximo", "clpid": "Garc\u00eda-Sucre-M" }, { "family_name": "Raseev", "given_name": "Gheorghe", "clpid": "Raseev-G" }, { "family_name": "Ross", "given_name": "Stephen C.", "clpid": "Ross-S-C" } ], "abstract": "A discussion is given to studies of Resonance Enhanced Multiphoton Ionization (REMPI) processes in molecules.", "doi": "10.1063/1.40552", "isbn": "0883188406", "publisher": "American Institute of Physics", "place_of_publication": "New York, NY", "publication_date": "1991-04-30", "pages": "132-135" }, { "id": "authors:5t64t-h5673", "collection": "authors", "collection_id": "5t64t-h5673", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151028-114733424", "type": "book_section", "title": "Collisions of polarized electrons with O_2", "book_title": "Half collision resonance phenomena in molecules", "author": [ { "family_name": "da Paix\u00e3o", "given_name": "Fernado J.", "clpid": "da-Paix\u00e3o-F-J" }, { "family_name": "Lima", "given_name": "Marco A. P.", "clpid": "Lima-M-A-P" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Garc\u00eda-Sucre", "given_name": "M\u00e1ximo", "clpid": "Garc\u00eda-Sucre-M" }, { "family_name": "Raseev", "given_name": "Gheorghe", "clpid": "Raseev-G" }, { "family_name": "Ross", "given_name": "Stephen C.", "clpid": "Ross-S-C" } ], "abstract": "Recently several methods have been developed and applied to studies of electron\u2010molecule collisions at low impact energies. These approaches include the R\u2010matrix, Linear algebraic, complex Kohn, and Schwinger multichannel (SMC) methods. In principle, these methods can account for important physical effects in such collisions which arise from open and closed electronic channels. In this paper we will report some results of preliminary studies of collisions of low\u2010energy electrons with molecular oxygen, an open\u2010shell system. In contrast to closed\u2010shell systems such as H_2 and N_2, the electron polarization may change in collisions with these open\u2010shell targets due to spin\u2010exchange processes. We have determined these spin\u2010exchange effects for elastic e\u2010O_2 collisions and found them to be much smaller than those seen in alkali atoms such as Na. Our results compare well with those of recent measurements of these effects for O_2 by Hanne and his collaborators.", "doi": "10.1063/1.40546", "isbn": "0883188406", "publisher": "American Institute of Physics", "place_of_publication": "New York, NY", "publication_date": "1991-04-30", "pages": "321-324" }, { "id": "authors:dv8jb-0p522", "collection": "authors", "collection_id": "dv8jb-0p522", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151028-114731324", "type": "book_section", "title": "Photoelectron spectroscopy of excited molecular states", "author": [ { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" }, { "family_name": "Braunstein", "given_name": "M.", "clpid": "Braunstein-M" }, { "family_name": "Rudolph", "given_name": "H.", "clpid": "Rudolph-H" }, { "family_name": "Stephens", "given_name": "J. A.", "clpid": "Stephens-J-A" }, { "family_name": "Dixit", "given_name": "S. N.", "clpid": "Dixit-S-N" }, { "family_name": "Lynch", "given_name": "D. L.", "clpid": "Lynch-D-L" } ], "abstract": "Results of studies of ion rotational and vibrational distributions for resonance enhanced multiphoton ionization are discussed.", "doi": "10.1063/1.39176", "publisher": "American Institute of Physics", "publication_date": "1990-04-01" }, { "id": "authors:t9axy-g1n24", "collection": "authors", "collection_id": "t9axy-g1n24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151120-141428672", "type": "book_section", "title": "Molecules in Intense Laser Fields", "book_title": "Atoms in Strong Fields", "author": [ { "family_name": "Dixit", "given_name": "S. N.", "clpid": "Dixit-S-N" }, { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Nicolaides", "given_name": "Cleanthes A.", "clpid": "Nicolaides-C-A" }, { "family_name": "Clark", "given_name": "Charles W.", "clpid": "Clark-C-W" }, { "family_name": "Nayfeh", "given_name": "Munir H.", "clpid": "Nayfeh-M-H" } ], "abstract": "Recent advances in tunable laser sources have stimulated a great deal of interest in the study of intense field-matter interaction physics. Whenever a molecule interacts with an intense radiation field, it can absorb multiple photons from the field and make a transition either to an excited state (excitation) or into the continuum (ionization). If the energy of an integral number of photons equals the energy difference between the initial and an excited state, the multiphoton process becomes resonant and its probability is greatly enhanced. The observation of such resonant enhanced processes requires considerably less intensity than that required for non-resonant processes. Several researchers have taken advantage of this resonance enhancement to study various aspects of resonant enhanced multiphoton ionization (REMPI) processes in molecules. Measurement of ionic and photoelectron spectra have illustrated features such as non-Franck-Condon effects in ionic vibrational branching ratios due to autoionization, shape resonances and Cooper minima, non-atomic effects in ionization of Rydberg states and competition between rotational and vibrational autoionization.", "doi": "10.1007/978-1-4757-9334-5_29", "isbn": "978-1-4757-9336-9", "publisher": "Springer", "place_of_publication": "New York, NY", "publication_date": "1990", "pages": "509-512" }, { "id": "authors:mq5ab-sht52", "collection": "authors", "collection_id": "mq5ab-sht52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151020-124811295", "type": "book_section", "title": "Studies of Electron-Molecule Collisions on the Mark IIIfp Hypercube", "book_title": "Proceedings of the Fifth Distributed Memory Computing Conference", "author": [ { "family_name": "Hipes", "given_name": "Paul", "clpid": "Hipes-P-G" }, { "family_name": "Winstead", "given_name": "Carl", "clpid": "Winstead-C" }, { "family_name": "Lima", "given_name": "Marco", "clpid": "Lima-M-A-P" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Walker", "given_name": "David W.", "clpid": "Walker-D-W" }, { "family_name": "Stout", "given_name": "Quentin F.", "clpid": "Stout-Q-F" } ], "abstract": "We report on a distributed memory implementation and initial applications of a program for calculating electron-molecule collision cross sections. Runs on the Mark IIIfp hypercube show that large-grain MIMD machines are well suited for these applications. Some results of studies of e^--Si_2H_6 and e^--SiF_4 collisions will be discussed.", "doi": "10.1109/DMCC.1990.555426", "isbn": "0-8186-2113-3", "publisher": "IEEE Computer Society", "place_of_publication": "Los Alamitos, CA", "publication_date": "1990", "pages": "498-503" }, { "id": "authors:bh57m-z5f35", "collection": "authors", "collection_id": "bh57m-z5f35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151120-123218285", "type": "book_section", "title": "Electron-Nitrogen Molecule Collisions in High-Temperature Nonequilibrium Air", "book_title": "Thermophysical aspects of re-entry flows", "author": [ { "family_name": "Hou", "given_name": "W. M.", "clpid": "Huo-W-M" }, { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" }, { "family_name": "Lima", "given_name": "M. A. P.", "clpid": "Lima-M-A-P" }, { "family_name": "Gibson", "given_name": "T. L.", "clpid": "Gibson-T-L" } ], "contributor": [ { "family_name": "Moss", "given_name": "James N.", "clpid": "Moss-J-N" }, { "family_name": "Scott", "given_name": "Carl D.", "clpid": "Scott-C-D" } ], "abstract": "Ab initio calculation of vibrational excitation and\nde-excitation cross sections of N_2 by low-energy resonant\nelectron impact have been carried out. The calculation\nincludes initial target state in v = 0-12 and final\ntarget state in v = 0-17. The calculated cross sections\nare found to agree with available experimental data to\nwithin reported experimental error. Effect of target\nrotation has been investigated. Comparison of vibrational\nexcitation cross sections at J = 0, 50, and 150 shows\nthat the major effect of target rotation is to lower the\nresonance energy. Vibrational excitation and de-excitation rate coefficients are tabulated for electron temperatures of 1100-55,000 K. The present tabulation supersedes an earlier compilation by the Naval Research Laboratory that was derived from experimental data with a factor-of-two error. The tabulated rate coefficients are suited for flowfield modeling of aeroassisted orbital transfer vehicles.", "doi": "10.2514/5.9781600865770.0152.0196", "isbn": "978-0-930403-10-2", "publisher": "American Institute of Aeronautics and Astronautics", "place_of_publication": "New York, NY", "publication_date": "1986", "pages": "152-196" }, { "id": "authors:606v2-1kk45", "collection": "authors", "collection_id": "606v2-1kk45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151120-134534673", "type": "book_section", "title": "Studies of Elastic and Electronically Inelastic Electron-Molecule Collisions", "book_title": "Swarm Studies and Inelastic Electron-Molecule Collisions", "author": [ { "family_name": "Lima", "given_name": "Marco A. P.", "clpid": "Lima-M-A-P" }, { "family_name": "Gibson", "given_name": "Thomas L.", "clpid": "Gibson-T-L" }, { "family_name": "Brescansin", "given_name": "Luiz M.", "clpid": "Brescansin-L-M" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" }, { "family_name": "Huo", "given_name": "Winifred M.", "clpid": "Huo-W-M" } ], "contributor": [ { "family_name": "Pitchford", "given_name": "Leanne C.", "clpid": "Pitchford-L-C" }, { "family_name": "McKoy", "given_name": "B. Vincent", "clpid": "McKoy-B-V" }, { "family_name": "Chutjian", "given_name": "Ara", "clpid": "Chutjian-A" }, { "family_name": "Trajmar", "given_name": "Sandor", "clpid": "Trajmar-S" } ], "abstract": "Cross-sections for the scattering of low-energy electrons by molecules play an important role in the modeling of swarm and plasma etching systems, gas lasers, and planetary atmospheres. In contrast to the related atomic problem, the progress to date in both theoretical and experimental studies of electron-molecule scattering cross-sections has been limited [1]. On the theoretical side, this situation is primarily due to the additional complexities arising from the nonspherical potential fields of molecular targets. Most studies of electronic excitation of molecules by low-energy electrons have hence been carried out using low-order theories. These include plane-wave theories such as the Born Ochkur-Rudge approximations [2, 3], the impact-parameter method [4], and distorted-wave theories [5, 6]. Several studies of elastic scattering by molecules have also used local approximations to the nonlocal exchange potentials [7]. Although such theories and approximations can be computationally easy to apply, they do not contain enough of the collision physics to yield consistently reliable differential and integral cross sections, particularly at low and intermediate energies [8]. What is clearly needed are theoretical methods which can provide quantitatively reliable cross-sections for the elastic and inelastic scattering of low-energy electrons by molecules.", "doi": "10.1007/978-1-4612-4662-6_37", "isbn": "978-1-4612-9104-6", "publisher": "Springer New York", "place_of_publication": "New York, NY", "publication_date": "1986", "pages": "239-264" }, { "id": "authors:gs6g9-9ba12", "collection": "authors", "collection_id": "gs6g9-9ba12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180404-153728354", "type": "book_section", "title": "Dynamics of Molecular Photoionization Processes", "book_title": "Resonances", "author": [ { "family_name": "Lynch", "given_name": "D. L.", "clpid": "Lynch-D-L" }, { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" }, { "family_name": "Lucchese", "given_name": "R. R.", "clpid": "Lucchese-R-R" } ], "abstract": "Increasing amounts of data have shown that shape resonances play an important role in molecular photoionization. These resonances can lead to significant deviations of the vibrational branching ratios from Franck-Condon predictions and to vibrational state dependence of the photoelectron asymmetry parameters. They are one-electron in nature and their properties are determined primarily by the molecular core potential. These features suggest that their role in photoionization should be studied using realistic molecular potentials and photoelectron continuum states. We will first discuss the relevant aspects of the method we have developed for studying the electronic Hartree-Fock continuum states needed in molecular photoionization. We will then present the results of applications of this approach to resonant photoionization in several molecules including N_2, CO, CO_2, C_2H_2, and C_2N_2. Our emphasis will be on a comparison of these results both with experimental data and other theoretical predictions.", "doi": "10.1021/bk-1984-0263.ch006", "isbn": "9780841208650", "publisher": "American Chemical Society", "place_of_publication": "Washington, DC", "publication_date": "1984-09-28", "pages": "89-112" }, { "id": "authors:5jknj-xy341", "collection": "authors", "collection_id": "5jknj-xy341", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151110-102838552", "type": "book_section", "title": "Dynamics of Molecular Photoionization Processes", "book_title": "Resonances in Electron-Molecule Scattering, van der Waals Complexes, and Reactive Chemical Dynamics", "author": [ { "family_name": "Lynch", "given_name": "D. L.", "clpid": "Lynch-D-L" }, { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" }, { "family_name": "Lucchese", "given_name": "R. R.", "clpid": "Lucchese-R-R" } ], "contributor": [ { "family_name": "Truhlar", "given_name": "Donald G.", "clpid": "Truhlar-D-G" } ], "abstract": "Increasing amounts of data have shown that shape resonances play an important role in molecular photoionization. These resonances can lead to significant deviations of the vibrational branching ratios from Franck-Condon predictions and to vibrational state dependence of the photoelectron asymmetry parameters. They are one-electron in nature and their properties are determined primarily by the molecular core potential. These features suggest that their role in photoionization should be studied using realistic molecular potentials and photoelectron continuum states. We will first discuss the relevant aspects of the method we have developed for studying the electronic Hartree-Fock continuum states needed in molecular photoionization. We will then present the results of applications of this approach to resonant photoionization in several molecules including N_2, CO, CO_2, C_2H_2, and C_2N_2. Our emphasis will be on a comparison of these results both with experimental data and other theoretical predictions.", "doi": "10.1021/bk-1984-0263.ch006", "isbn": "0-8412-0865-4", "publisher": "American Chemical Society", "place_of_publication": "Washington, DC", "publication_date": "1984-09-28", "pages": "89-112" }, { "id": "authors:s2w16-3td21", "collection": "authors", "collection_id": "s2w16-3td21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151120-113206090", "type": "book_section", "title": "Electronic Excitation of Molecules by Electron Impact", "book_title": "Wavefunctions and Mechanisms from Electron Scattering Processes", "author": [ { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" }, { "family_name": "Lee", "given_name": "Mu-Tao", "clpid": "Lee-Mu-Tao" } ], "contributor": [ { "family_name": "Gianturco", "given_name": "F. A.", "clpid": "Gianturco-F-A" }, { "family_name": "Stefani", "given_name": "G.", "clpid": "Stefani-G" } ], "abstract": "In this talk I will review the recent progress that has been made in the theoretical determination of differential and integral cross sections for the electronic excitation of molecules by low-energy electrons. Whereas there has been considerable progress in the development and application of theoretical methods for treating inelastic electron-atom scattering [1], the situation is quite different for the related molecular problem. It is well-known that this difference is ultimately due to the difficulties associated with the nonspherical nature of the electron-molecule force field. In fact, it was not until the 1960's that a renewed interest in processes involving H2 and N2 resulted in the application of plane-wave theories to treat the excitation of electronic states in these molecules. In the last five years more advanced theories such as the distorted-wave method, the impact-parameter method, and the close-coupling method have been applied to the description of electron impact excitation of diatomic molecules. The results of these more recent applications, and their comparison with available experimental data, will be the focal point of my presentation. We will see that, although the results of some of these theoretical applications are encouraging, there are substantial disagreements between both the predictions of the different methods themselves, and with the experimental data. There clearly remains a serious need for further development of theoretical methods for the prediction of electron impact excitation cross sections of both linear and polyatomic molecules.", "doi": "10.1007/978-3-642-46502-4_32", "isbn": "978-3-540-13347-6", "publisher": "Springer", "place_of_publication": "New York, NY", "publication_date": "1984", "pages": "196-205" }, { "id": "authors:3qpcn-fhj92", "collection": "authors", "collection_id": "3qpcn-fhj92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151119-071534218", "type": "book_section", "title": "The Schwinger Variational Principle: An Approach to Electron-Molecule Collisions", "book_title": "Electron-Atom and Electron-Molecule Collisions", "author": [ { "family_name": "Lucchese", "given_name": "R. R.", "clpid": "Lucchese-R-R" }, { "family_name": "Takatsuka", "given_name": "K.", "clpid": "Takatsuka-Kazuo" }, { "family_name": "Watson", "given_name": "D. K.", "clpid": "Watson-D-K" }, { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Hinze", "given_name": "Juergen", "clpid": "Hinze-J" } ], "abstract": "In this contribution we want to discuss several features and\napplications of the Schwinger variational principle to the study of collisions of low energy electrons with molecules and molecular ions . The Schwinger variational principle has long been known to be a potentially useful formulation of the collision problem but until recently there have been very few applications of this variational principle to electron collision problems, The main drawback to the application of the Schwinger variational principle to more realistic systems has generally been regarded as the occurence of the term < \u03c8^(-)_k \u2502V G_0 V\u2502 \u03c8^(+)_k > in the variational functional. Historically this drawback seems to have outweighed the possible distinct advantages which the Schwinger variational principle is known to have over other standard variational methods such as the Kohn principle. One of these advantages results from the feature that the trial scattering wave function need not satisfy any specific\nasymptotic boundary conditions. This feature implies both\nthat the trial wave function could be expanded exclusively in terms of discrete basis functions, if such expansions were advantageous in the particular problem, and that irregular functions, which must be regularized near the origin, are not required in the trial function. Moreover, the Schwinger method is not troubled by the spurious\nsingularities that can arise in the Kohn variational method.\nAlthough various ways for avoiding the effects of these singularities in such methods have been developed it is a desirable feature of a method to be free of such singularities.", "doi": "10.1007/978-1-4899-2148-2_3", "isbn": "978-1-4899-2150-5", "publisher": "Springer", "publication_date": "1983", "pages": "29-49" }, { "id": "authors:eqzmk-9js45", "collection": "authors", "collection_id": "eqzmk-9js45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151123-092124616", "type": "book_section", "title": "Studies of Molecular Photoionization", "book_title": "Electron-Molecule Collisions and Photoionization Processes", "author": [ { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" }, { "family_name": "Lucchese", "given_name": "Robert", "clpid": "Lucchese-R-R" } ], "contributor": [ { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" }, { "family_name": "Suzuki", "given_name": "Hirosi", "clpid": "Suzuki-Hirosi" }, { "family_name": "Takayanagi", "given_name": "Kazuo", "clpid": "Takayanagi-Kazuo" }, { "family_name": "Trajmar", "given_name": "Sandor", "clpid": "Trajmar-S" } ], "abstract": "It is becoming increasingly clear that, due to the\navailability of high-resolution electron spectrometers\nutilizing synchrotron light sources, increasing amounts of\ndata containing detailed dynamical information on molecular\nphotoionization are being produced. Such data have already\nshown that shape and autoionizing resonances play a very\nimportant role in molecular photoionization processes. For\nexample, these resonant processes can induce significant\ndeviations of the vibrational branching ratios from those\nbased on Franck-Condon factors and also lead to photoelectron asymmetry parameters which depend strongly on the final vibrational state of the ion. The availability of such data is stimulating the development and application of theoretical methods for studying molecular photoionization processes at the appropriate quantitative level.", "isbn": "0-89573-134-7", "publisher": "Verlag Chemie International", "place_of_publication": "Deerfield Beach, Fla.", "publication_date": "1983", "pages": "13-20" }, { "id": "authors:ctw1v-2j095", "collection": "authors", "collection_id": "ctw1v-2j095", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151119-074827197", "type": "book_section", "title": "The Schwinger and related variational principles in electron-molecule collision processes", "author": [ { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" }, { "family_name": "Lucchese", "given_name": "Robert", "clpid": "Lucchese-R-R" }, { "family_name": "Takatsuka", "given_name": "Kazuo", "clpid": "Takatsuka-Kazuo" } ], "contributor": [ { "family_name": "Eissner", "given_name": "W.", "clpid": "Eissner-W" } ], "abstract": "An iterative approach to the solution of the Lippmann-Schwinger integral equation for electron-molecule scattering, based on the use of the Schwinger variational principle is outlined. Application of the theory to electron-molecule collisions at the static-exchange level and for use with optical potentials, and a new variational principle for the strong polar molecule case, are discussed. Results of some applications of these methods to a few systems are considered and some results of the use of the method for molecular photoionization are presented. Multichannel extensions of the Schwinger variational principle are discussed and some results as applied to a simple and exactly soluble two-channel model problem presented.", "publisher": "Science and Engineering Research Council", "publication_date": "1982-03" }, { "id": "authors:sxtfq-hwv59", "collection": "authors", "collection_id": "sxtfq-hwv59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151119-070052370", "type": "book_section", "title": "The Equations of Motion Method: An Approach to the Dynamical Properties of Atoms and Molecules", "book_title": "Methods of Electronic Structure Theory", "author": [ { "family_name": "McCurdy", "given_name": "Clyde W., Jr.", "clpid": "McCurdy-C-W-Jr" }, { "family_name": "Rescigno", "given_name": "Thomas N.", "clpid": "Rescigno-T-N" }, { "family_name": "Yeager", "given_name": "Danny L.", "clpid": "Yeager-D-L" }, { "family_name": "McKoy", "given_name": "Vincent", "clpid": "McKoy-V" } ], "contributor": [ { "family_name": "Schaefer", "given_name": "Henry F., III", "clpid": "Schaefer-H-F-III" } ], "abstract": "This chapter is concerned with the equations of motion method as a many-body approach to the dynamical properties of atoms and molecules. In a wide range of spectroscopic experiments one is primarily concerned with just dynamical properties. These dynamical properties include excitation energies and oscillator strengths in optical spectroscopy, the dynamic or frequency-dependent polarizability in light scattering studies, photoionization cross sections, and elastic and inelastic electron scattering cross sections. These experiments probe the response of an atom or molecule to some external perturbation. If one is concerned with these properties one should develop a formalism which aims directly at these properties. Of course this idea is not novel. For example, one might try to calculate the appropriate Green's functions whose poles, and residues at these poles, are directly the excitation energies and transitions densities, respectively. One could also attempt to solve the time-dependent Schr\u00f6dinger equation directly, e.g., in the time-dependent Hartree\u2014Fock approximation. The approach to these dynamical properties of atoms and molecules which we will discuss is based on the equations of motion formalism as suggested by Rowe.(1) This is a very practical formalism based on the equations of motion for excitation operators defined as operators that convert one stationary state of a system into another state.", "doi": "10.1007/978-1-4757-0887-5_9", "isbn": "978-1-4757-0889-9", "publisher": "Springer", "publication_date": "1977", "pages": "339-386" }, { "id": "authors:68eet-wvy21", "collection": "authors", "collection_id": "68eet-wvy21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151118-133505273", "type": "book_section", "title": "Rydberg States of Diatomic and Polyatomic Molecules", "book_title": "Chemical Spectroscopy and Photochemistry in the Vacuum-Ultraviolet", "author": [ { "family_name": "McKoy", "given_name": "V.", "clpid": "McKoy-V" }, { "family_name": "Betts", "given_name": "T.", "clpid": "Betts-T" } ], "contributor": [ { "family_name": "Sandorfy", "given_name": "C.", "clpid": "Sandorfy-C" }, { "family_name": "Ausloos", "given_name": "P. J.", "clpid": "Ausloos-P-J" }, { "family_name": "Robin", "given_name": "M. B.", "clpid": "Robin-M-B" } ], "abstract": "Rydberg states clearly play an important role in the study of the electronic structure of atoms and molecules in the vacuum ultraviolet. Moreover many molecules, including diatomic and simpler polyatomic types of particular importance in astrophysics, aeronomy and photochemistry\u2014such as H_2, O_2, NO, N_2, CO, CO_2, H_2O, C_6H_6\u2014have their most important and strongest electronic bands in the vacuum ultraviolet. Interest in this spectral region has been stimulated both by the improved resolution of optical absorption studies and by the development of techniques such as electron impact spectroscopy. From electron impact spectroscopy one can now obtain accurate spectra of molecules well into the vacuum ultraviolet quite readily. In the analysis of such electron impact spectra one must know the location and nature of several Rydberg series. From several recent experiments it has also become obvious that the Rydberg series in many molecules can perturb the intravalence region of the spectrum and lead to some unusual features in the term values and intensity distribution. We will return to this point shortly. Rydberg series also lead to several important features in photoionization cross sections. With the increased resolution and activity in the measurement of photoionization cross sections we can expect a renewed\ninterest in this role of Rydberg series. Finally a knowledge of the quantum defects in a Rydberg series can provide useful information on the phase shifts for electron-molecule scattering.", "doi": "10.1007/978-94-010-2153-1_20", "isbn": "978-94-010-2155-5", "publisher": "Springer", "place_of_publication": "New York, NY", "publication_date": "1974-08", "pages": "317-336" } ]