[ { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/pff5m-ydw47", "eprint_id": 66901, "eprint_status": "archive", "datestamp": "2023-08-20 04:48:47", "lastmod": "2023-10-18 19:11:48", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "Lutfur R." } }, { "id": "Perry-J-W", "name": { "family": "Perry", "given": "Joseph W." } }, { "id": "Hanson-J-E", "name": { "family": "Hanson", "given": "James E." } }, { "id": "Dervan-P-B", "name": { "family": "Dervan", "given": "Peter B." }, "orcid": "0000-0001-8852-7306" } ] }, "title": "Weak Temperature Dependence of Electron Transfer Rates in Fixed-Distance Porphyrin-Quinone Model Systems", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1994 American Chemical Society. \n\nReceived April 13, 1994. \n\nThis work was performed in part at the Jet Propulsion Laboratory (JPL), California Institute of Technology, and was supported in part by the Department of Energy through an agreement with the National Aeronautics and Space Administration (NASA). P.B.D. and J.E.H. thank the National Science Foundation for financial support. Additional support from the Director's Discretionary Fund at JPL is gratefully acknowledged. L.R.K. thanks NASA and the National Research Council for a Resident Research Associateship at JPL and Dr. John Miller (Argonne National Laboratories) for providing us with data on temperature-dependent dielectric constants and densities of 2MTHF. We thank Profs. David Beratan, Jose Onuchic, John Hopfield, and Rudy Marcus for many helpful discussions.", "abstract": "Electron transfer rate constants of several derivatives of [5-(4'-(4\"-(2\"',5\"'-benzoquinonyl)bicyclo[2.2.2]octyl)\nphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrinato]zinc(II) have been measured as a function of temperature\nin 2-methyltetrahydrofuran, toluene, and toluene-d_g. The observed temperature dependencies of the electron transfer\nrate constants are relatively weak in both the polar and nonpolar solvents. Nonexponential ET dynamics are observed\nat low temperatures and described in terms of an initial (k_(ET)^0) and an average ET rate constant (k_(av)). The k_(ET)^0 values\nfor the molecules with different driving forces, spanning a range of 0.2 eV, show parallel trends over the range of\ntemperatures studied. The trends in k_(ET)^0 are described in terms of the effects of temperature-dependent changes in\nsolvent dielectric constants on the barrier height. Good agreement is observed for the case of toluene solvent, using\na semiclassical model, but poorer quantitative agreement is found for the 2-methyltetrahydrofuran data. The temperature\ndependence of k_(av) is described using a model incorporating an angle-dependent electronic coupling and interconversion\nof rotational conformers. A temperature-dependent solvent isotope effect is observed on going from toluene to toluene-d_8,\nwith k_(ET)^0( toluene)/k_(ET)^0( toluene-d_8) being as large at 1.5 over the range of temperatures studied.", "date": "1994-10-19", "date_type": "published", "publication": "Journal of the American Chemical Society", "volume": "116", "number": "21", "publisher": "American Chemical Society", "pagerange": "9700-9709", "id_number": "CaltechAUTHORS:20160510-110420134", "issn": "0002-7863", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160510-110420134", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)" }, { "agency": "NASA" }, { "agency": "NSF" }, { "agency": "JPL Director's Discretionary Fund" }, { "agency": "National Research Council" } ] }, "doi": "10.1021/ja00100a040", "resource_type": "article", "pub_year": "1994", "author_list": "Khundkar, Lutfur R.; Perry, Joseph W.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/kfm58-7yx63", "eprint_id": 4102, "eprint_status": "archive", "datestamp": "2023-08-22 07:45:37", "lastmod": "2023-10-23 19:34:31", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "Lutfur R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "Ahmed H." } } ] }, "title": "Ultrafast molecular reaction dynamics in real-time: progress over a decade", "ispublished": "pub", "full_text_status": "public", "keywords": "ultrafast chemistry, femtosecond chemistry, reaction dynamics, IVR, transition states", "note": "\"Reprinted, with permission, from the Annual Review of Physical Chemistry, Volume 41 copyright 1990 by Annual Reviews, www.annualreviews.org\" \n\nOver the last ten years, this research was supported primarily by the National Science Foundation and the Air Force Office of Scientific Research, hereby gratefully acknowledged. The efforts and dedication of a great number of graduate students and post-doctoral fellows, acknowledged in this review, have made this research possible. A.H.Z. wishes to thank R. A. Marcus, R. B. Bernstein, and R. Bersohn for many stimulating discussions; the fruits of some collaborations are acknowledged in the text. We are grateful to all our colleagues who provided us with preprints and reprints of their work. We hope that we were successful in including all relevant contributions and apologize to those whose work we did not have a chance to discuss. L.R.K. would like to thank the National Research Council for support through a postdoctoral Resident Research Associateship at the Jet Propulsion Laboratory, Caltech, administered by the NASA.\n\n
Published - KHUarpc90.pdf
", "abstract": "One of the goals of researchers in the field of reaction dynamics is to develop an understanding of the elementary steps involved in a chemical reaction on a molecular level (see e.g. Ref. 1). The century-old Arrhenius rate law, a phenomenological description of the temperature dependence of rates of reactions in bulk, has been used extensively to deduce activation energies and frequency factors. The activated complex theory (also referred to as absolute rate theory or transition-state theory, see e.g. Refs. 2, 3) postulated more than 50 years ago, provides a useful interpretation of the Arrhenius rate parameters in terms of molecular properties. These parameters contain practical information about rates, but they do not express the molecular details of a reaction. At this juncture, two types of questions can be raised--one concerning the effects of the environment on rates in condensed media, and the other, the purely molecular aspects of reactions in the absence of an environment, i.e. in an isolated molecular system. We restrict our attention to the latter case for the purposes of this review.", "date": "1990-10", "date_type": "published", "publication": "Annual Review of Physical Chemistry", "volume": "41", "publisher": "Annual Reviews", "pagerange": "15-60", "id_number": "CaltechAUTHORS:KHUarpc90", "issn": "0066-426X", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:KHUarpc90", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF" }, { "agency": "Air Force Office of Scientific Research (AFOSR)" }, { "agency": "National Research Council" }, { "agency": "NASA/JPL/Caltech" } ] }, "primary_object": { "basename": "KHUarpc90.pdf", "url": "https://authors.library.caltech.edu/records/kfm58-7yx63/files/KHUarpc90.pdf" }, "resource_type": "article", "pub_year": "1990", "author_list": "Khundkar, Lutfur R. and Zewail, Ahmed H." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/c740v-zn356", "eprint_id": 70063, "eprint_status": "archive", "datestamp": "2023-08-19 22:25:03", "lastmod": "2023-10-20 21:22:45", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "Lutfur R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "Ahmed H." } } ] }, "title": "Picosecond photofragment spectroscopy. IV. Dynamics of consecutive bond breakage in the reaction C_2F_4I_2\u2192C_2F_4+ 2I", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1990 American Institute of Physics. \n\nReceived 12 May 1989 Accepted 25 September 1989. \n\nThis research was supported by the National Science Foundation. We wish to thank Dr. J. L. Knee, Dr. B. Reid, Professor R. Bersohn, and Professor Y. T. Lee for many stimulating discussions. We also thank A. J. Hoffman for help with the experiments and N. Kurur and Dr. J. Yesinowski ( C. I. T. ) for their assistance in obtaining the ^(19)F NMR\nspectrum of our sample. Finally, we would like to express our sincere thanks to the referee for a critical reading of the manuscript and many helpful comments.\n\nPublished - 1.458469.pdf
", "abstract": "Picosecond photofragment spectroscopy of the ultraviolet (UV)photodissociation of 1,2\u2010diiodotetrafluoroethane reveals consecutive breaking of the two C\u2013I bonds. Spin\u2013orbit excited (I^*) atoms show a prompt rise, in agreement with a direct mode dissociation of the first bond. Ground\u2010state (I) atoms show a biexponential buildup, one component being fast (\u22641 ps) while the other component is slow (30\u2013150 ps depending on total energy), characteristic of the second bond breaking. The transient behavior of I atoms changes with the available energy. These results are interpreted in terms of a two step model involving a weakly bound radical. Simulations of transient behavior of I atoms, based on estimated internal energy distributions from the primary step and a model for dissociation rates as a function of energy, suggest that surface crossings are relevant to the dynamics and that the quantum yield of I atoms varies with excitation energy.", "date": "1990-01-01", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "92", "number": "1", "publisher": "American Institute of Physics", "pagerange": "231-242", "id_number": "CaltechAUTHORS:20160831-093457095", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160831-093457095", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF" } ] }, "other_numbering_system": { "items": [ { "id": "7949", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.458469", "primary_object": { "basename": "1.458469.pdf", "url": "https://authors.library.caltech.edu/records/c740v-zn356/files/1.458469.pdf" }, "resource_type": "article", "pub_year": "1990", "author_list": "Khundkar, Lutfur R. and Zewail, Ahmed H." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/3ph53-vkn80", "eprint_id": 70061, "eprint_status": "archive", "datestamp": "2023-08-19 22:06:06", "lastmod": "2023-10-20 21:22:37", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Potter-E-D", "name": { "family": "Potter", "given": "E. D." } }, { "id": "Gruebele-M", "name": { "family": "Gruebele", "given": "M." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "A. H." } } ] }, "title": "Picosecond dissociation of ketene: Experimental state-to-state rates and tests of statistical theories", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1990 Elsevier Science Publishers B.V. \n\nReceived 29 September 1989; in final form 5 October 1989. \n\nThe authors would like to thank Professor Rudolph A. Marcus for helpful discussions, and Professor C. Bradley Moore for many helpful discussions and correspondence of unpublished results. We would also like to thank Amy Hoffman for assistance with some of the (000) measurements. This work was supported by a grant from the National Science Foundation CHE 8512887.", "abstract": "The state-to-state dissociation rates of ketene have been measured for a variety of singlet methylene rotational states in both the ground and (010) vibrational levels of the methylene fragment. Measured time constants range from 1.0 ns at 500 cm^(\u22121) to 19 ps at 5600 cm^(\u22121) above threshold. The measurements cannot be accounted for by simple phase space theory (PST), which has been used to explain product state distributions, or tight transition state RRKM theory, but are in good agreement with variational RRKM theory. The estimated threshold rate of 2\u00d710^8 s^(\u22121) is in agreement with the previous lower limit of 7\u00d710^7 s^(\u22121) of Chen, Green and Moore.", "date": "1989-12-22", "date_type": "published", "publication": "Chemical Physics Letters", "volume": "164", "number": "5", "publisher": "Elsevier", "pagerange": "463-470", "id_number": "CaltechAUTHORS:20160831-091534634", "issn": "0009-2614", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160831-091534634", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CHE-8512887" } ] }, "other_numbering_system": { "items": [ { "id": "8039", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1016/0009-2614(89)85239-X", "resource_type": "article", "pub_year": "1989", "author_list": "Potter, E. D.; Gruebele, M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/6j422-3jn19", "eprint_id": 10292, "eprint_status": "archive", "datestamp": "2023-08-22 06:03:13", "lastmod": "2023-10-16 22:47:03", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Klippenstein-S-J", "name": { "family": "Klippenstein", "given": "S. J." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "A. H." } }, { "id": "Marcus-R-A", "name": { "family": "Marcus", "given": "R. A." }, "orcid": "0000-0001-6547-1469" } ] }, "title": "Application of unimolecular reaction rate theory for highly flexible transition states to the dissociation of NCNO into NC and NO", "ispublished": "pub", "full_text_status": "public", "keywords": "CHEMICAL REACTION KINETICS, DISSOCIATION, NITROGEN COMPOUNDS, OXYGEN COMPOUNDS, CARBON COMPOUNDS, VIBRATIONAL STATES, DISTRIBUTION, PHASE SPACE", "note": "\u00a9 1988 American Institute of Physics. \n\nReceived 7 June 1988; accepted 11 July 1988. \n\nIt is a pleasure to acknowledge the support of this research by the National Science Foundation. We are indebted to Professor G. Segal for providing us with results of his calculated potential energy surfaces and to Professor H. Reisler for supplying the experimental data used in Figs. 16 and 17. \n\nArthur Amos Noyes Laboratory of Chemical Physics, Contribution No. 7788.\n\nPublished - KLIjcp88.pdf
", "abstract": "A recently described method for implementing RRKM theory for unimolecular reactions with highly flexible transition states is applied to the calculation of energy and angular momentum resolved rate constants and rotational\u2013vibrational energy distributions for the reaction NCNO-->h nu NCNO*-->NCNO(vib. hot)-->NC+NO. The dissociation rate results are compared to the recent experimental results of Khundkar et al., and the vibrational and rotational distribution results are compared to the experimental values of Nadler et al. Comparison is also made with phase space theory calculations. The calculated rotational distributions at energies below the vibrational threshold of the products are the same as those of PST. At energies (2348, 2875 cm^\u22121) above this threshold energy the rovibrational distribution is in better agreement with the data than is that of PST. The need for obtaining more accurate ab initio potential energy surfaces is noted, particularly for treating reactions at still higher energies.", "date": "1988-10-15", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "89", "number": "8", "publisher": "American Institute of Physics", "pagerange": "4761-4770", "id_number": "CaltechAUTHORS:KLIjcp88", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:KLIjcp88", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF" } ] }, "other_numbering_system": { "items": [ { "id": "7788", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.455670", "primary_object": { "basename": "KLIjcp88.pdf", "url": "https://authors.library.caltech.edu/records/6j422-3jn19/files/KLIjcp88.pdf" }, "resource_type": "article", "pub_year": "1988", "author_list": "Klippenstein, S. J.; Khundkar, L. R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/2kfg2-g7w83", "eprint_id": 70163, "eprint_status": "archive", "datestamp": "2023-08-19 20:00:50", "lastmod": "2023-10-20 21:53:51", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "Luftur R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "Ahmed H." } } ] }, "title": "Picosecond MPI mass spectrometry of CH_3I in the process of dissociation", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1987 lsevier Science Publishers B.V. \n\nReceived 5 November 1987. \n\nThis work was supported by the Air Force Office of Scientific Research, Contract No. AFOSR-87-0071. We thank Professor J.C. Polanyi for providingus with a preprint of his work on HD_2. One of us (AHZ) wishes to acknowledge fruitful and enlightening discussions with Professor R. Bersohn on absorption during dissociation while here at Caltech.", "abstract": "Picosecond multiphoton ionization and time-of-flight mass spectrometry has been used to monitor the dissociation of methyl iodide excited to its A continuum. The measured signals show a rapid buildup when the probe laser is tuned to a resonance of free atomic iodine and a sharp feature at zero time delay when it is tuned off-resonance. Enhanced signal is also observed in the parent ion channel. These results illustrate the possible use of this technique for the probing of fragment species before they are completely separated from their partners in a half-collision process.", "date": "1987-12-18", "date_type": "published", "publication": "Chemical Physics Letters", "volume": "142", "number": "5", "publisher": "Elsevier", "pagerange": "426-432", "id_number": "CaltechAUTHORS:20160906-090610524", "issn": "0009-2614", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160906-090610524", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Air Force Office of Scientific Research (AFOSR)", "grant_number": "87-0071" } ] }, "other_numbering_system": { "items": [ { "id": "7695", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1016/0009-2614(87)85137-0", "resource_type": "article", "pub_year": "1987", "author_list": "Khundkar, Luftur R. and Zewail, Ahmed H." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/eqffg-2p896", "eprint_id": 70165, "eprint_status": "archive", "datestamp": "2023-08-19 20:00:42", "lastmod": "2023-10-20 21:54:06", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Scherer-N-F", "name": { "family": "Scherer", "given": "N. F." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Rose-T-S", "name": { "family": "Rose", "given": "T. S." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "A. H." } } ] }, "title": "Sub-Doppler measurement of excited-state rotational constants and rotational coherence by picosecond multiphoton ionization mass spectrometry", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1987 American Chemical Society. \n\nReceived: September 3, 1987. \n\nWe thank Mr. Spencer Baskin and Dr. Peter Felker for enlightening discussions. The computer simulation done here benefited from these discussions and from the work presented in ref 1 and 2. This work was supported by a grant from the National Science Foundation (DMR-8521191).", "abstract": "A method is presented here for one-photon sub-Doppler measurement of excited-state rotational constants and coherence of large polyatomic molecules. The method, which relies on the concept of purely rotational coherence in molecules, utilizes (polarized) picosecond pumpprobe multiphoton ionization (MPI) mass spectrometry. It offers improved temporal resolution (pulse width limited) and is applicable to weakly or nonfluorescing molecules. The present implementation in a molecular beam provides measurements of the rotational constants in the excited (SI) state of trans-stilbene and gives information on\nthe direction of the relevant transition moments involved. From the coherence decay of the initially prepared state we obtain the dephasing time, which we discuss in relation to experiments involving vibrational/rotational energy redistribution.", "date": "1987-12-17", "date_type": "published", "publication": "Journal of Physical Chemistry", "volume": "91", "number": "26", "publisher": "American Chemical Society", "pagerange": "6478-6483", "id_number": "CaltechAUTHORS:20160906-090611093", "issn": "0022-3654", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160906-090611093", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMR-8521191" } ] }, "other_numbering_system": { "items": [ { "id": "7605", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1021/j100310a012", "resource_type": "article", "pub_year": "1987", "author_list": "Scherer, N. F.; Khundkar, L. R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ga98h-mp350", "eprint_id": 70168, "eprint_status": "archive", "datestamp": "2023-08-19 19:44:01", "lastmod": "2023-10-20 21:54:20", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Scherer-N-F", "name": { "family": "Scherer", "given": "Norbert F." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "Lutfur R." } }, { "id": "Bernstein-R-B", "name": { "family": "Bernstein", "given": "Richard B." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "Ahmed H." } } ] }, "title": "Real-time picosecond clocking of the collision complex in a bimolecular reaction: The birth of OH from H+CO_2", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1987 American Institute of Physics. \n\nReceived 13 April 1987; accepted 12 May 1987. \n\nResearch supported by the National Science Foundation under Grant No. DMR-8521191.\n\nPublished - 1.453280.pdf
", "abstract": "Picosecond (and femtosecond) photofragment spectroscopy has recently provided time-resolved, state-to-state dynamics of molecular photofragmentation. The focus of these experiments was on unimolecular reactions, where two main issues are fundamental to the dynamics: the nature of the \"half-collision\" and the degree to which statistical theories account for the time evolution of product state distributions (PSDs).", "date": "1987-07-15", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "87", "number": "2", "publisher": "American Institute of Physics", "pagerange": "1451-1453", "id_number": "CaltechAUTHORS:20160906-090612033", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160906-090612033", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMR-8521191" } ] }, "other_numbering_system": { "items": [ { "id": "7572", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.453280", "primary_object": { "basename": "1.453280.pdf", "url": "https://authors.library.caltech.edu/records/ga98h-mp350/files/1.453280.pdf" }, "resource_type": "article", "pub_year": "1987", "author_list": "Scherer, Norbert F.; Khundkar, Lutfur R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/zfnns-2je95", "eprint_id": 70216, "eprint_status": "archive", "datestamp": "2023-08-19 19:43:23", "lastmod": "2023-10-20 21:57:56", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "Lutfur R." } }, { "id": "Knee-J-L", "name": { "family": "Knee", "given": "Joseph L." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "Ahmed H." } } ] }, "title": "Picosecond photofragment spectroscopy. I. Microcanonical state-to-state rates of the reaction NCNO\u2192CN+NO", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1987 American Institute of Physics. \n\nReceived 09 December 1986 Accepted 11 February 1987. \n\nContribution No. 7513.\n\nPublished - 1.453527.pdf
", "abstract": "This paper, the first in a series of three papers, gives a detailed account of our studies on picosecond photofragment spectroscopy. The unimolecular reaction NCNO\u2192CN+NO is examined in detail here. Microcanonical state\u2010to\u2010state rates are measured in molecular beams at different energies in the reagent NCNO using pump\u2013probe techniques: one picosecond pulse initiates the reaction from an initial (v,J) state and a second pulse, delayed in time, monitors the CN radical product in a specific rovibrational state, or the reagent NCNO (transient absorption). The threshold energy for reaction is determined to be 17\u2009083 cm^(\u22121) (bond energy=48.8 kcal/mol). Measured rates are found to be sharply dependent on the total energy of the reagent, but independent of the rotational quantum state of product CN. Results of transient absorption measurements are used to argue that the ground statepotential energy surface dominates the reaction in the range of excess energies studied. The energy dependence of the rates, k_(MC)(E), is compared with that predicted by statistical theories. Both standard RRKM (tight transition state) and phase space theory (loose transition state) fail to reproduce the data over the full range of energies studied, even though nascent product state distributions are known to be in accord with PST at these energies. Furthermore, k_(MC)(E) is not a strictly monotonically increasing function of energy but exhibits some structure which cannot be explained by simple statistical theories. We advance some explanations for this structure and deviations from statistical theories.", "date": "1987-07-01", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "87", "number": "1", "publisher": "American Institute of Physics", "pagerange": "77-96", "id_number": "CaltechAUTHORS:20160908-154009568", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160908-154009568", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "other_numbering_system": { "items": [ { "id": "No. 7513", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.453527", "primary_object": { "basename": "1.453527.pdf", "url": "https://authors.library.caltech.edu/records/zfnns-2je95/files/1.453527.pdf" }, "resource_type": "article", "pub_year": "1987", "author_list": "Khundkar, Lutfur R.; Knee, Joseph L.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/h5ajs-rt686", "eprint_id": 70169, "eprint_status": "archive", "datestamp": "2023-08-19 19:43:13", "lastmod": "2023-10-20 21:54:25", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Knee-J-L", "name": { "family": "Knee", "given": "Joseph L." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "Lutfur R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "Ahmed H." } } ] }, "title": "Picosecond photofragment spectroscopy. III. Vibrational predissociation of van der Waals' clusters", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1987 American Institute of Physics. \n\nReceived 09 December 1986 Accepted 11 February 1987. \n\nThis work was supported by a grant from the National Science Foundation (DMR 85-21191).\n\nPublished - 1.453608.pdf
", "abstract": "This paper, last in this series, reports on the picosecond dynamics of vibrational predissociation in beam\u2010cooled van der Waals' clusters. Reaction rates have been measured for clusters (1:1) of phenol and cresol (p\u2010methylphenol) with benzene by the picosecond pump\u2013probe photoionization mass\u2010spectrometry technique. Dissociation to form phenol (cresol) and benzene takes place from vibrational levels of the S_1 state of phenol (cresol) prepared by the pump laser. The predissociation rates were measured for a number of different excess energies upto \u223c2500 cm^(\u22121), and the reaction threshold was found to be 1400 cm^(\u22121) above the S_1 origin for phenol\u2013benzene and \u223c1795 cm^(\u22121) for cresol\u2013benzene, respectively. For phenol\u2013benzene, the predissociation rates, following excitation of ring\u2010type modes, vs excess energy vary more or less smoothly. Cresol\u2013benzene exhibits biexponential decay, with the fast component becoming more dominant at higher energies. A non\u2010RRKM model involving division of the vibrational phase space is discussed to explain this observation.", "date": "1987-07-01", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "87", "number": "1", "publisher": "American Institute of Physics", "pagerange": "115-127", "id_number": "CaltechAUTHORS:20160906-090612288", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160906-090612288", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMR 85-21191" } ] }, "other_numbering_system": { "items": [ { "id": "7515", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.453608", "primary_object": { "basename": "1.453608.pdf", "url": "https://authors.library.caltech.edu/records/h5ajs-rt686/files/1.453608.pdf" }, "resource_type": "article", "pub_year": "1987", "author_list": "Knee, Joseph L.; Khundkar, Lutfur R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/js9zy-01595", "eprint_id": 70465, "eprint_status": "archive", "datestamp": "2023-08-19 18:24:54", "lastmod": "2023-10-20 23:00:21", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "Lutfur R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "Ahmed H." } } ] }, "title": "Exciton and vibronic effects in the spectroscopy of bianthracene in supersonic beams", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1986 American Institute of Physics. \n\nReceived 01 October 1985 Accepted 30 October 1985. \n\nIt is a pleasure to acknowledge the National Science Foundation (Grant No. DMR-8521191) for its support of this research. We also thank Dr. Jack A. Syage and Dr. Peter M. Felker for their generous assistance in recording the spectra and for many helpful discussions.\n\nPublished - 1.450521.pdf
", "abstract": "Excitation and dispersed fluorescence spectra of 9,9'\u2010bianthracene in a supersonic expansion are reported. The spectra are anthracene\u2010like, indicating that the rings are weakly coupled. Exciton effects are considered in the interpretation of the spectra. The torsional potential in S_1 is modeled as a double\u2010well (Gaussian perturbation on a one\u2010dimensional harmonic oscillator) with barriers to perpendicularity and planarity of \u223c30 and \u223c1100 cm^(\u22121), respectively. The S_0 torsional potential shows negative anharmonicity which is modeled as a quartic perturbation. Anthracenic modes in S_1 and S_0 are also assigned. Finally, measurements of S_1 fluorescence lifetimes up to \u223c6000 cm^(\u22121) excess energy in the excited state show no evidence of charge transfer.", "date": "1986-02-01", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "84", "number": "3", "publisher": "American Institute of Physics", "pagerange": "1302-1311", "id_number": "CaltechAUTHORS:20160920-105243107", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160920-105243107", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMR-8521191" } ] }, "other_numbering_system": { "items": [ { "id": "7306", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.450521", "primary_object": { "basename": "1.450521.pdf", "url": "https://authors.library.caltech.edu/records/js9zy-01595/files/1.450521.pdf" }, "resource_type": "article", "pub_year": "1986", "author_list": "Khundkar, Lutfur R. and Zewail, Ahmed H." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0vfw8-3jv95", "eprint_id": 70469, "eprint_status": "archive", "datestamp": "2023-08-19 18:02:23", "lastmod": "2023-10-20 23:00:40", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Knee-J-L", "name": { "family": "Knee", "given": "J. L." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "Ahmed H." } } ] }, "title": "Picosecond Photofragmentation of Tri- and Tetraatomlc Molecules: Measurement of \"State-to-State\" Reaction Rates", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1985 American Chemical Society. \n\nReceived: August 19, 1985. \n\nThis work was supported by a grant from the National Science Foundation. We thank Prof. C. Wittig, Dr. H. Reisler, and Dr. M. Noble for many helpful discussions on the preparation of NCNO and phase space calculations. A.H.Z. acknowledges many stimulating discussions with Prof. R. Bernstein-near the French Alps.", "abstract": "In this Letter, we report our first results on the picosecond measurements of state-to-state rates of reactions, involving three and four-atom molecules. These photofragment reactions are ICN \u2192 I + CN and NCNO \u2192 NO + CN. In these experiments, we use one picosecond pulse to initiate the photolysis and a second pulse to probe the produced fragments in their internal vibrational/rotational states. Results are presented for molecules in bulbs and beams, and comparisons with unimolecular theories are given.", "date": "1985-10-01", "date_type": "published", "publication": "Journal of Physical Chemistry", "volume": "89", "number": "22", "publisher": "American Chemical Society", "pagerange": "4659-4663", "id_number": "CaltechAUTHORS:20160920-130849155", "issn": "0022-3654", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160920-130849155", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF" } ] }, "other_numbering_system": { "items": [ { "id": "7301", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1021/j100268a001", "resource_type": "article", "pub_year": "1985", "author_list": "Knee, J. L.; Khundkar, L. R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/s7d77-ap611", "eprint_id": 11556, "eprint_status": "archive", "datestamp": "2023-08-22 04:28:10", "lastmod": "2023-10-17 15:08:16", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Knee-J-L", "name": { "family": "Knee", "given": "J. L." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "A. H." } } ] }, "title": "Picosecond monitoring of a chemical reaction in molecular beams: Photofragmentation of R\u2013I\u2192R\u2021+I", "ispublished": "pub", "full_text_status": "public", "keywords": "MOLECULAR BEAMS, MONITORING, REACTION INTERMEDIATES, TIME RESOLUTION, METHYL IODIDE, PHOTOCHEMICAL REACTIONS, FRAGMENTATION, CHEMICAL REACTIONS, MASS SPECTROSCOPY", "note": "\u00a9 1985 American Institute of Physics. \n\nReceived 15 May 1985; accepted 11 June 1985. \n\nThis research was supported by a grant from the National Science Foundation. We thank Professor R. Marcus, Professor R. Bernstein, Professor W. Goddard, and Professor J. Beauchamp for enlightening discussions. This work was presented at the International Conference \"Recent Advances in Molecular Reaction Dynamics,\" Aussois, France, June 1985. \n\n[A.H.Z. was a] Camille and Henry Dreyfus Teacher-Scholar. \n\nArthur Amos Noyes Laboratory of Chemical Physics, Contribution No. 7189.\n\nPublished - KNEjcp85c.pdf
", "abstract": "Studies of chemical reactions by molecular beam techniques and spectroscopic methods have provided extensive information on the nature of the intermediates involved and on the energy distribution in products.(1-6) Until now, however, there is no report of direct picoseconds time resolution of a chemical reaction in molecular beams.", "date": "1985-08-15", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "83", "number": "4", "publisher": "American Institute of Physics", "pagerange": "1996-1998", "id_number": "CaltechAUTHORS:KNEjcp85c", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:KNEjcp85c", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF" }, { "agency": "Camille and Henry Dreyfus Foundation" } ] }, "other_numbering_system": { "items": [ { "id": "7189", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.449339", "primary_object": { "basename": "KNEjcp85c.pdf", "url": "https://authors.library.caltech.edu/records/s7d77-ap611/files/KNEjcp85c.pdf" }, "resource_type": "article", "pub_year": "1985", "author_list": "Knee, J. L.; Khundkar, L. R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/dhk1v-5fm28", "eprint_id": 70472, "eprint_status": "archive", "datestamp": "2023-08-19 17:53:25", "lastmod": "2023-10-20 23:00:54", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Knee-J-L", "name": { "family": "Knee", "given": "J. L." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "A. H." } } ] }, "title": "IVR in Isolated Molecules with Nearby Electronic States", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1985 American Chemical Society. \n\nReceived: May 28, 1985. \n\nThis research was supported by the National Science Foundation under Grant No. DMR-8105034. We also thank Professor E. Lim for providing us with information on the modes of isoquinoline in the n\u03c0^* state, and for useful discussions.", "abstract": "In this Letter, we report direct picosecond measurements of decay rates in a beam of isoquinoline, excited to different vibrational states in the second (S_2) excited electronic state (\u03c0\u03c0^*). IVR and IER are discussed in relation to the proximity of the S_2 electronic state to a nearby S_1 (n\u03c0^*) electronic state, and to internal conversion to the ground state.", "date": "1985-07-18", "date_type": "published", "publication": "Journal of Physical Chemistry", "volume": "89", "number": "15", "publisher": "American Chemical Society", "pagerange": "3201-3202", "id_number": "CaltechAUTHORS:20160920-130849976", "issn": "0022-3654", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160920-130849976", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMR-8105034" } ] }, "other_numbering_system": { "items": [ { "id": "7196", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1021/j100261a008", "resource_type": "article", "pub_year": "1985", "author_list": "Knee, J. L.; Khundkar, L. R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/bd5qr-zzj85", "eprint_id": 11555, "eprint_status": "archive", "datestamp": "2023-08-22 04:23:34", "lastmod": "2023-10-17 15:08:14", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Knee-J-L", "name": { "family": "Knee", "given": "J. L." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "A. H." } } ] }, "title": "Picosecond mass spectrometry of a collisionless photodissociation reaction", "ispublished": "pub", "full_text_status": "public", "keywords": "PHOTODISSOCIATION, PS RANGE, MASS SPECTROSCOPY, MOLECULAR BEAMS, BENZENE, DYE LASERS, PHENOL, COMPLEXES", "note": "\u00a9 1985 American Institute of Physics. \n\nReceived 11 February 1985; accepted 8 March 1985. \n\nThis work was supported by the National Science Foundation under Grant No. DMR-8105034. \n\n[A.H.Z. was a] Camille and Henry Dreyfus Foundation Teacher-Scholar. \n\nArthur Amos Noyes Laboratory of Chemical Physics, Contribution No. 7152.\n\nPublished - KNEjcp85b.pdf
", "abstract": "We wish to report on the direct observation (in real time) of a photodissociation reaction under collisionless conditions. This is achieved by the technique of picosecond mass spectrometry in skimmed molecular beams.", "date": "1985-05-15", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "82", "number": "10", "publisher": "American Institute of Physics", "pagerange": "4715-4716", "id_number": "CaltechAUTHORS:KNEjcp85b", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:KNEjcp85b", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMR-8105034" }, { "agency": "Camille and Henry Dreyfus Foundation" } ] }, "other_numbering_system": { "items": [ { "id": "7152", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.448681", "primary_object": { "basename": "KNEjcp85b.pdf", "url": "https://authors.library.caltech.edu/records/bd5qr-zzj85/files/KNEjcp85b.pdf" }, "resource_type": "article", "pub_year": "1985", "author_list": "Knee, J. L.; Khundkar, L. R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ypjg8-mzs49", "eprint_id": 11478, "eprint_status": "archive", "datestamp": "2023-08-22 03:55:05", "lastmod": "2023-10-16 23:49:03", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Courtney-S-H", "name": { "family": "Courtney", "given": "S. H." } }, { "id": "Fleming-G-R", "name": { "family": "Fleming", "given": "G. R." } }, { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "A. H." } } ] }, "title": "Unimolecular reaction rates in solution and in the isolated molecule: Comparison of diphenyl butadiene nonradiative decay in solutions and supersonic jets", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1984 American Institute of Physics. \n\nReceived 24 January 1984; accepted 29 February 1984. \n\nThis work was supported by grants from the National Science Foundation to G.R.F. and A.H.Z. \n\n[A.H.Z. was a] Camille & Henry Dreyfus Foundation Teacher-Scholar. \n\nArthur Amos Noyes Laboratory of Chemical Physics, Contribution No. 6693.\n\nPublished - COUjcp84.pdf
", "abstract": "The recent study of diphenyl butadiene (DPB) in supersonic jets and in solution by Shepanski et al.(1) and by Courtney and Felming(2), respectively, provides an opportunity to compare the isomerization rates measured in the isolated molecule (jet) with those measured at very low viscosity in solution. These comparisons should shed light on the vibrational energy flows between \"optical\" and \"reactive\" modes in the isolated molecule and on the connection between activated, friction dependent, models of barrier crossing in solution,(3-5) and statistical RRK (or RRKM) theories of gas phase unimolecular reactions(6).", "date": "1984-05-01", "date_type": "published", "publication": "Journal of Chemical Physics", "volume": "80", "number": "9", "publisher": "American Institute of Physics", "pagerange": "4559-4560", "id_number": "CaltechAUTHORS:COUjcp84", "issn": "0021-9606", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:COUjcp84", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF" }, { "agency": "Camille and Henry Dreyfus Foundation" } ] }, "other_numbering_system": { "items": [ { "id": "6693", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1063/1.447211", "primary_object": { "basename": "COUjcp84.pdf", "url": "https://authors.library.caltech.edu/records/ypjg8-mzs49/files/COUjcp84.pdf" }, "resource_type": "article", "pub_year": "1984", "author_list": "Courtney, S. H.; Fleming, G. R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ke6kd-bkk49", "eprint_id": 58578, "eprint_status": "archive", "datestamp": "2023-08-19 16:05:14", "lastmod": "2023-10-23 19:29:46", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Khundkar-L-R", "name": { "family": "Khundkar", "given": "L. R." } }, { "id": "Marcus-R-A", "name": { "family": "Marcus", "given": "R. A." }, "orcid": "0000-0001-6547-1469" }, { "id": "Zewail-A-H", "name": { "family": "Zewail", "given": "A. H." } } ] }, "title": "Unimolecular reactions at low energies and RRKM behavior: isomerization and dissociation", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1983 American Chemical Society.\n\nReceived: April 18, 1983.\n\nIt is a pleasure to acknowledge the support of this work by the National Science Foundation. L.R.K. is grateful to the Exxon Educational Foundation for a graduate fellowship during the course of this work.", "abstract": "Rates of isomerization of electronically excited trans-stilbene and of the dissociation of isoquinoline-solvent\ncomplexes in jet beams are compared with those expected from RRKM theory as a function of energy; the\ncomparison is made at low vibrational energies (~1200-3000 cm^(-1)). The jet result for the threshold energy\nof the isomerization is compared with the activation energy for the reaction in solution. The two values are\nin good agreement.", "date": "1983-07", "date_type": "published", "publication": "Journal of Physical Chemistry", "volume": "87", "number": "14", "publisher": "American Chemical Society", "pagerange": "2473-2476", "id_number": "CaltechAUTHORS:20150624-095555455", "issn": "0022-3654", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150624-095555455", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF" }, { "agency": "Exxon Educational Foundation" } ] }, "other_numbering_system": { "items": [ { "id": "6826", "name": "Arthur Amos Noyes Laboratory of Chemical Physics" } ] }, "doi": "10.1021/j100237a008", "resource_type": "article", "pub_year": "1983", "author_list": "Khundkar, L. R.; Marcus, R. A.; et el." } ]