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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenThu, 28 Mar 2024 11:02:01 -0700The Elastic Scattering of Protons by F¹⁹ and N¹⁴
https://resolver.caltech.edu/CaltechETD:etd-02252004-110707
Year: 1955
DOI: 10.7907/7GKE-MN22
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
The elastic scattering of protons by F19 and N14 has been investigated in the proton energy range 550 to 1800 kev. For F19(p,p) the differential cross section has been measured for proton energies from 550 to 1800 kev at center-of-mass angles of 90, 125.3, and 159.8 degrees and for proton energies from 1300 to 1500 kev at 53.2, 60, 70, 80, 100, 110, and 136 degrees. Pronounced scattering anomalies were observed near [...] and 1700 kev. For N14(p,p) the cross section has been measured from 600 to 1800 kev at 154 degrees and from 1.0 to 1.1 and 1.4 to 1.8 Mev at 90 and 125.3 degrees. Anomalies were observed near [...] and 1.79 ([...]) Mev. The indicated spin and parity assignments are required by the results of these experiments. The relative stopping cross section for protons in LiF has been measured for proton energies from 400 to 1600 kev, and experimental and theoretical investigations of the effects of finite energy resolution on observed cross sections have been made.https://resolver.caltech.edu/CaltechETD:etd-02252004-110707On the Recombination Rate of Iodine Atoms in the Presence of Various Gases
https://resolver.caltech.edu/CaltechETD:etd-02062006-102644
Year: 1959
DOI: 10.7907/KAVE-WG75
<p>The rate of iodine atom recombination in the presence of various gases has been studied by the flash photolysis technique. The temperature dependence of the rate constant has been determined for recombination in helium, hydrogen, benzene, and methyl iodide. The negative temperature dependences are fitted by the form, k∝1/T<sup>n</sup>, where n(He) = 0.80, n(H<sub>2</sub> = 1.48, n(C<sub>6</sub>H<sub>6</sub> = 2.53, and n(CH<sub>3</sub>I = 3.24.</p>
<p>The iodine atom recombination rate constant was also measured at 50°C. for ethyl iodide, hydrogen iodide, carbon monoxide, and nitric oxide. The rate constants relative to helium at 50°C. are: <br />
<br />
He      1.00       C<sub>2</sub>H<sub>5</sub>I    179.<br />
H<sub>2</sub>       3.33       NI         21.1 <br />
C<sub>6</sub>H<sub>6</sub>   61.1       CO       4.07 <br />
CH<sub>3</sub>I    88.8       NO       >1.4 x 10<sup>4</sup> <br />
<br />
Nitric oxide appears to be a very efficient third body gas and only a lower limit on the rate constant could be established.</p>
<p>Calculations have been made for some possible mechanisms of iodine atom recombination. A classical three body collision model is proposed for atom recombinations. The classical equations of motion were programmed to be solved numerically on a digital computer and some trajectories were examined.</p>https://resolver.caltech.edu/CaltechETD:etd-02062006-102644The Beta Spectra of the Mass 12 Nuclei
https://resolver.caltech.edu/CaltechTHESIS:08232011-105654839
Year: 1962
DOI: 10.7907/4BW8-8827
<p>This thesis, "The Beta Spectra of the Mass 12 Nuclei," is mainly concerned with an experimental test of the conserved-vector-current theory. This theory predicts a deviation from the allowed shape of the B<sup>12</sup> and N<sup>12</sup> beta spectra. The ratio of the shape factor of the two spectra is expected to have an energy dependence of 1.10 ± 0.17 percent per Mev. If the CVC hypothesis is not invoked, this ratio is estimated to be an order of magnitude smaller. The two spectra have been measured with a magnetic spectrometer and found to give for this ratio the value 1.30 ± 0.31 percent per Mev. In addition the branching fraction of the N<sup>12</sup> decay to the 7.6-Mev state of C<sup>12</sup> has been determined to be 3.0 ± 0.5 percent. The geometrical mean of the two shape factors was observed to have an unexpected linear energy dependence of 1.18 percent per Mev. Theoretical estimates are made of relevant matrix elements in search of an understanding of this. Baffle penetration by the beta particles gives a systematic effect estimated to account for about one third of the observed mean shape factor. The uncertainty in this estimate precludes a definite conclusion on the actual presence of this term in the spectra. Such penetration is expected, however, to have little influence on the conserved vector current theory test. A preliminary report of this work has been published (1, 2).</p>
https://resolver.caltech.edu/CaltechTHESIS:08232011-105654839Flow Generated by Suddenly Heated Flat Plate
https://resolver.caltech.edu/CaltechETD:etd-10052004-163535
Year: 1963
DOI: 10.7907/CPQD-RQ29
<p>By employing the two-sided Maxwellian in Maxwell's moment method a kinetic theory description is obtained of the flow generated by a step-function increase in the temperature of an infinite flat plate. Four moments are employed in order to satisfy the three conservation equations, plus one additional equation involving the heat flux in the direction normal to the plate. For a small temperature rise the equations are linearized, and closed-form solutions are obtained for small and large time in terms of the average collision time.</p>
<p>Initially the disturbances propagate along two distinct characteristics, but the discontinuities across these waves damp out as time increases. At large time the main disturbance propagates with the isentropic sound speed. Solutions for mean normal velocity and temperature show the transition from the nearly collision-free regime to the Navier-Stokes-Fourier regime, which is characterized by a boundary layer near the plate surface merging into a diffuse "wave". The classical continuum equations, plus a temperature jump boundary condition, seem to be perfectly adequate to describe the flow beyond a few collision times, provided one accounts properly for the interaction between the inner thermal layer and the outer diffuse wave.</p>https://resolver.caltech.edu/CaltechETD:etd-10052004-163535Experiments on the Upstream Wake in Magneto-Fluid Dynamics
https://resolver.caltech.edu/CaltechETD:etd-12082005-111323
Year: 1963
DOI: 10.7907/NAR6-M485
<p>Measurements have been made of the perturbation magnetic field in front of a semi-infinite Rankine body moving parallel to a uniform impressed magnetic field in a conducting fluid. The purpose of these experiments was to investigate the so-called upstream wake effect which has been predicted by theory. It is believed that these are the first experiments in which the upstream wake was observed. Although the wake was found to exist as predicted when the Alfvén number is greater than one, its decay behavior was remarkably different from that which was predicted. The solutions for infinite medium predicted that in the wake the perturbations should decay inversely as the distance from the body. However the experiments showed that the perturbations decayed exponentially. It was finally shown that this change in the decay behavior was an effect of the walls and the conducting material surrounding the fluid.</p>
https://resolver.caltech.edu/CaltechETD:etd-12082005-111323Gamma Radiation from the Alpha Particle Bombardment of C¹²
https://resolver.caltech.edu/CaltechETD:etd-09272002-140450
Year: 1965
DOI: 10.7907/PG1J-B583
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
The excitation function of the reaction C12([alpha], [gamma])016 has been studied over the region E[subscript alpha] = 2.8 to 8.3 MeV using a NaI(T1) detector and enriched C12 targets. Resonances were observed at E[subscript alpha] = 3.24, 3.58, 4.26, 5.81, 7.05, 7.88 and 8.13 MeV, corresponding to 016 states at E[subscript x]= 9.59, 9.85, 10.36, 11.52, 12.45, 13.07 and 13.26 MeV. Radiative widths [Gamma subscript gamma] for ground state radiation from the states at 9.59, 9.85, 11.52 and 12.45 MeV were measured to be 0.022 [plus or minus] 0.005, 0.0059 [plus or minus] 0.0006, 0.66 [plus or minus] 0.09 and 7 [plus or minus] 1 eV, respectively. Radiative widths for cascade radiation from the 9.85 and 10.36 MeV states through intermediate states of 016 were measured to be 0.0012 [plus or minus] 0.0004 and 0.046 [plus or minus] 0.006 eV, respectively. Interference effects in ground state radiation from the 13.07 MeV([...]) state support evidence for an underlying 2+ state at nearly the same energy. Other information on excited states of 016 is presented.https://resolver.caltech.edu/CaltechETD:etd-09272002-140450The determination of small time differences in the formation of planetary objects
https://resolver.caltech.edu/CaltechETD:etd-03092009-160704
Year: 1970
DOI: 10.7907/D5S4-JN64
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
A new solid source single focusing, sector magnet mass spectrometer was developed with a programmable magnetic field analyzer of stability [...]. Digital data are obtained during a completely automatic sequence and include the real time at which an intensity measurement is made. An on line computer analyses the data and returns the results to the operator throughout a run. The precision obtained in measuring isotopic ratios is increased by an order of magnitude over conventional similar instruments and is documented for the strontium isotopes. The [...] ratio is measured to better than [...] 0.007% over the extended time of the experiments.
Ca-rich achondritic meteorites having a total spread of 0.2% in [...] were studied and appear to define an identical initial abundance of 0.698983 [...] 0.000032. The samples lie on a well defined isochron with slope 0.0642 [...] 0.0034, corresponding to an age of 4.47 [...] 0.24 x [...] years. The maximum deviation of data points from the isochron is 6 x [...] and shows that these samples were formed over a time interval of 1.6 x [...] years if they were derived from an environment of solar Rb/Sr abundance. The Angra dos Reis achondrite has the distinctly lower inital Sr composition of 0.69884 [...] 0.00004 and is, therefore, derived from more primitive material than any other meteorite measured. Angra dos Reis may have formed 5.4 x [...] years earlier than the other achondrites (from a solar Rb/Sr environment). The Angra dos Reis initial Sr isotopic composition should be considered as the best estimate of the primordial Sr isotopic abundance in the solar system.
Measurements on the chondrite Guarena yield an age 4.56 [...] 0.08 x [...] years and precise Sr initial composition of 0.69995 [...] 0.00015. This is evidence for either a late formation of Guarena or a metamorphic event taking place 74 x [...] years after the time of formation of the Ca-rich achondrites. These measurements may yield a time index for the classification of meteorites.
Measurements on Apollo XI lunar samples are presented and discussed.
https://resolver.caltech.edu/CaltechETD:etd-03092009-160704