Measurements and Quasi-Quantum Modeling of the Steric Asymmetry and Parity Propensities in State-to-State Rotationally Inelastic Scattering of NO (2Π1/2) with D2

Relative integrated cross sections are measured for spin−orbit-conserving, rotationally inelastic scattering of NO (2Π1/2), hexapole-selected in the upper Λ-doublet level of the ground rotational state (j = 0.5), in collisions with D2 at a nominal energy of 551 cm-1. The final state of the NO molecu...

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Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2007-08, Vol.111 (31), p.7631-7639
Main Authors: Taatjes, Craig A, Gijsbertsen, Arjan, de Lange, Marc J. L, Stolte, Steven
Format: Article
Language:English
Subjects:
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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Summary:Relative integrated cross sections are measured for spin−orbit-conserving, rotationally inelastic scattering of NO (2Π1/2), hexapole-selected in the upper Λ-doublet level of the ground rotational state (j = 0.5), in collisions with D2 at a nominal energy of 551 cm-1. The final state of the NO molecule is detected by laser-induced fluorescence (LIF). The state-selected NO molecule is oriented with either the N end or the O end toward the incoming D2 molecule by application of a static electric field E in the scattering region. This field is directed parallel or antiparallel to the relative velocity vector v. Comparison of signals taken for the different applied field directions gives the experimental steric asymmetry SA, defined by SA = (σ v ↑↓ E − σ v ↑↑ E )/(σ v ↑↓ E + σ v ↑↑ E ), which is equal to within a factor of −1 to the molecular steric effect, S i → f ≡ (σD 2 → NO − σD 2 → ON)/(σD 2 → NO + σD 2 → ON). The dependence of the integral inelastic cross section on the incoming Λ-doublet component is also measured as a function of the final rotational (j final) and Λ-doublet (εfinal) state. The measured steric asymmetries are similar to those previously observed for NO−He scattering. Spin−orbit manifold-conserving collisions exhibit a larger propensity for parity conservation than their NO−He counterparts. The results are interpreted in the context of the recently developed quasi-quantum treatment (QQT) of rotationally inelastic scattering [Gijsbertsen, A.; Linnartz, H.; Taatjes, C. A.; Stolte, S. J. Am. Chem. Soc. 2006, 128, 8777]. The QQT predictions can be inverted to obtain a fitted hard-shell potential that reproduces the experimental steric asymmetry; this fitted potential gives an empirical estimate of the anisotropy of the repulsive interaction between NO and D2. QQT computation of the differential cross section using this simple model potential shows reasonable agreement with the measured differential cross sections.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp0712405