Jeff Nolte

ROVIBRATIONAL QUENCHING RATE COEFFICIENTS OF HD IN COLLISIONS WITH He

Along with H2, HD has been found to play an important role in the cooling of the primordial gas for the formation of the first stars and galaxies. It has also been observed in a variety of cool molecular astrophysical environments. The rate of cooling by HD molecules requires knowledge of collisional rate coefficients with the primary impactors, H, He, and H2. To improve knowledge of the collisional properties of HD, we present rate coefficients for the He-HD collision system over a range of collision energies from 10–5 to 5 × 103 cm–1. Fully quantum mechanical scattering calculations were performed for initial HD rovibrational states of j = 0 and 1 for v = 0-17 which utilized accurate diatom rovibrational wave functions. Rate coefficients of all Δv = 0, –1, and –2 transitions are reported. Significant discrepancies with previous calculations, which adopted a small basis and harmonic HD wave functions for excited vibrational levels, were found for the highest previously considered vibrational state of v = 3. Applications of the He-HD rate coefficients in various astrophysical environments are briefly discussed.

Final-state-resolved charge exchange in C5 + collisions with H

We report charge exchange cross sections for the collision system C5 + + H using the quantum mechanical molecular-orbital close-coupling method. The multi-reference single- and double-excitation configuration interaction method is used to produce potential and coupling data, and scattering calculations are performed for collision energies between 0.01 eV/u to 1 keV/u for all l,S-resolved states within the n = 3 and 4 manifolds. The n = 5 manifold is represented through the inclusion of the 5s state. To predict cross sections at higher energies, we include new results from atomic-orbital close-coupling and classical trajectory Monte Carlo calculations. We briefly discuss applications to x-ray emission within the solar system.