Classical study of rotational excitation of a rigid rotor: Li+ plus H2

Classical trajectory study of rotationally inelastic scattering of hydrogen molecules by collisions with lithium ion

Calculated collision induced absorption spectrum for He-Ar

Calculation of collision induced absorption spectra for helium-argo

Calculated Scattering Cross Sections for He☒He at Thermal Energies

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71197/2/JCPSA6-40-3-917-1.pd

C13 and Deuterium Isotope Effects in the Photolysis of Methyl and Ethyl Bromide

Relative rates of formation of isotopic radicals in the photolysis of gaseous methyl and ethyl bromide have been measured. Photolyses (2537 A) were carried out in a large excess of cyclopentane. Methyl (or ethyl) radicals formed in the primary C☒Br bond scission abstract H from cyclopentane to form methane (or ethane). For methyl bromide, the C12/C13 enrichment factor for the first fraction of the methane was 1.039±0.003. The corresponding factor for the α‐carbon—Br rupture in ethyl bromide was 1.041±0.004. In the deuterium experiments, CH3Br—CD3Br mixtures in excess cyclopentane were photolyzed. The H/D fractionation factor (based on CH4/CD3H) was 1.41±0.01.The difference in rates of formation of isotopic radicals is due to the difference in ultraviolet absorption coefficients of the isotopic alkyl bromides. At 2537 A the observed ratio of the extinction coefficient of CH3Br relative to that of CD3Br is 1.38±0.05.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71079/2/JCPSA6-30-4-973-1.pd

Velocity Dependence of the Differential Cross Sections for the Scattering of Atomic Beams of K and Cs by Hg

Measurements of the velocity dependence of the angular intensity distribution of potassium and cesium beams scattered by a crossed beam of mercury are presented. The alkali beam was velocity selected, with a triangular velocity distribution (half‐intensity width 4.7% of peak velocity); the velocity was varied over the range 185–1000 m/sec. The Hg beam had a thermal distribution; the average Hg speed was ∼235 meters per second. The scattering data have been converted to the center‐of‐mass system. The angular distributions show the expected strong forward scattering and evidence the phenomenon of rainbow scattering. The energy dependence of the rainbow angle is used to evaluate the interatomic potential well depth, interpreted as the dissociation energy De of the 2Σ+ molecular ground state. Values (in erg×1014) thus obtained (±5%) are 7.46 for KHg and 7.72 for CsHg. Absolute values of differential cross sections could not be obtained; only relative cross sections D(θ) are reported. The observed low‐angle behavior D(θ) ∝θ‐ 7/3 serves as direct experimental confirmation of the r—6 dependence of the long‐range attractive potential for K☒Hg and Cs☒Hg systems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69910/2/JCPSA6-37-9-2019-1.pd

Single-shot optical conductivity measurement of dense aluminum plasmas

The optical conductivity of a dense femtosecond laser-heated aluminum plasma heated to 0.1-1.5 eV was measured using frequency-domain interferometry with chirped pulses, permitting simultaneous observation of optical probe reflectivity and probe pulse phase shift. Coupled with published models of bound-electron contributions to the conductivity, these two independent experimental data yielded a direct measurement of both real and imaginary components of the plasma conductivity.DOE National Nuclear Security Administration DE-FC52-03NA00156Physic

Globular Cluster Abundances from High-Resolution Integrated Light Spectra, I: 47 Tuc

We describe the detailed chemical abundance analysis of a high-resolution (R~35,000), integrated-light (IL), spectrum of the core of the Galactic globular cluster 47 Tuc, obtained using the du Pont echelle at Las Campanas. We develop an abundance analysis strategy that can be applied to spatial unresolved extra- galactic clusters. We have computed abundances for Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Ba, La, Nd and Eu. For an analysis with the known color-magnitude diagram (cmd) for 47 Tuc we obtain a mean [Fe/H] value of -0.75 +/-0.026+/-0.045 dex (random and systematic error), in good agreement with the mean of 5 recent high resolution abundance studies, at -0.70 dex. Typical random errors on our mean [X/Fe] ratios are 0.07-0.10 dex, similar to studies of individual stars in 47 Tuc, although Na and Al appear enhanced, perhaps due to proton burning in the most luminous cluster stars. Our IL abundance analysis with an unknown cmd employed theoretical Teramo isochrones; however, we apply zero-point abundance corrections to account for the factor of 3 underprediction of stars at the AGB bump luminosity. While line diagnostics alone provide only mild constraints on the cluster age (ruling-out ages younger than ~2 Gyr), when theoretical IL B-V colors are combined with metallicity derived from the Fe I lines, the age is constrained to 10--15 Gyr and we obtain [Fe/H]=-0.70 +/-0.021 +/-0.052 dex. We find that Fe I line diagnostics may also be used to constrain the horizontal branch morphology of an unresolved cluster. Lastly, our spectrum synthesis of 5.4 million TiO lines indicates that the 7300-7600A TiO window should be useful for estimating the effect of M giants on the IL abundances, and important for clusters more metal-rich than 47 Tuc.Comment: 40 pages text & references, 4 tables, 19 figures (72 pages total). Changes include addition of B-V color to help constrain GC age. To appear in Ap

Molecular collisions. 16: Comparison of GPS with classical trajectory calculations of rotational inelasticity for the Ar-N2 system

Comparison of generalized phase shift treatment with classical trajectory calculations of rotational inelasticity cross sections of Ar-N2 scatterin