A new crossed beam approach to vibrationally inelastic scattering in neutral collision systems. State-to-state cross sections for He+I sup * sub 2 (. upsilon. prime =15, 25, 35) at E sub c. m. =89 meV

Journal Article · Fri Dec 15 04:00:00 EST 1989 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.457239· OSTI ID:5016400

Krajnovich, D J; Butz, K W; Du, H; Parmenter, C S ^[1]

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1. Department of Chemistry, Indiana University, Bloomington, Indiana 47405 (US)

Details are given of a new type of crossed beam experiment that is designed to study state-resolved vibrationally inelastic scattering of neutral atoms from neutral diatomics or polyatomics. The molecule is initially excited to a selected vibrational level in an excited electronic state by laser pumping. Dispersed fluorescence from molecules that have undergone inelastic scattering is used to observe the final vibrational state distributions. The technique is used here to characterize the vibrationally inelastic scattering of He from each of three initial levels {upsilon}{prime}=15, 25 and 35 within the {ital B}0{sup +}{sub {ital u}} state of I{sub 2}. The center-of-mass collision energy is 89 meV (720 cm{sup {minus}1}). Thirty cross sections (relative, not absolute) for vibrationally inelastic scattering are obtained. The cross sections characterize processes with vibrational quantum changes extending to {Delta}{upsilon}={plus minus}3 for the initial level {upsilon}{prime}=15, to {Delta}{upsilon}={plus minus}5 for {upsilon}{prime}=25, and to {Delta}{upsilon}={plus minus}7 for {upsilon}{prime}=35. Relative cross sections for pure rotationally inelastic scattering within the initially pumped {upsilon}{prime} levels are also reported. The data analysis incorporates much new information about I{sub 2} predissociation, spectroscopy, and Franck--Condon factors that has become available within the last ten years. An error analysis of the cross sections has been performed so that they are suitable benchmarks for theoretical calculation. Procedures are given for estimating fluorescence signal intensities in experiments of this type. The signal expectations are consistent with the I{sub 2} observations and suggest that extension to certain polyatomics is quite feasible.

• OSTI ID: 5016400
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 91:12; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
ATOMIC BEAMS
BEAMS
COLLISIONS
ELEMENTS
ENERGY LEVELS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EV RANGE
EXCITED STATES
FLUIDS
GASES
HALOGENS
HELIUM
IODINE
MILLI EV RANGE
MOLECULAR BEAMS
MOLECULE COLLISIONS
NONMETALS
RARE GASES
VIBRATIONAL STATES