Theoretical investigation of rotational rainbow structures in X--Na/sub 2/ collisions using CI potential surfaces. II. Combined rotational--vibrational excitation for X = He scattering

Journal Article · Sat Aug 01 04:00:00 EDT 1981 · J. Chem. Phys.; (United States)

OSTI ID:6315235

Mueller, W; Schinke, R

Combined rotational--vibrational excitaton cross sections for He--Na/sub 2/ scattering are reported for collision energies of 0.05< or =E< or =0.15 eV. The infinite-order-sudden (IOS) approximation is used to decouple the rotational and the orbital angular momenta, whereas the vibrational degree of freedom is treated exactly by solving vibrationally coupled radial equations. An analytical potential energy surface obtained from 160 ab initio CI energies is used in these scattering calculations. The cross sections for vibrational excitation or de-excitation are extremely small compared to the vibrationally elastic cross sections but increase rapidly with the collision energy. The influence of the target vibration on pure rotational excitation processes is negligibly small for energies considered in this study, such that the rigid-rotor approximation applied previously for the same system is confirmed to be reasonable. Furthermore, the rotational rainbow structures which are characteristic for the He--Na/sub 2/ system depend only very slightly on whether the molecule is initially in the ground n = 0 or the first vibrationally excited state n = 1. This was in contradiction to the experimental finding of Bergmann et al. (J. Chem. Phys. 72, 4777 (1980)), who reported a dramatic enhancement of the rotational energy transfer for scattering within the n = 1 vibrational state. The rotational rainbow maxima occur at almost equal positions independent of whether the transition is vibrationally elastic or inelastic. A small shift to wider scattering angles in the case of ..delta..n = 1 is observed at lower energies.

• Research Organization: Fachbereich Chemie, Universitaet Kaiserslautern, 6750 Kaiserslautern, West Germany
• OSTI ID: 6315235
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 75:3; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular &amp; Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ALKALI METALS
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
COLLISIONS
CONFIGURATION INTERACTION
CROSS SECTIONS
ELEMENTS
ENERGY
ENERGY LEVELS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EV RANGE
EV RANGE 01-10
EXCITATION
EXCITED STATES
FLUIDS
GASES
HELIUM
METALS
MOLECULE COLLISIONS
NONMETALS
POTENTIAL ENERGY
RARE GASES
ROTATIONAL STATES
SODIUM
VIBRATIONAL STATES