Rotationally specific rates of vibration-vibration energy exchange in collisions of NO(X 2II1/2, v=3) with NO(X 2II, v=0)

Meez Islam, Ian W. M. Smith

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Infrared ultraviolet double resonance (IRUVDR) experiments have been performed to investigate the rotational specificity of the vibrational-vibrational (V-V) exchange process, NO(X 2II1/2,ν = 3,Ji) + NO(ν = 0)→NO(X 2II1/2,ν = 2,Jf) + NO(ν=1), for which the vibrational energy discrepancy corresponds to 55.9 cm-1. Radiation from an optical parametric oscillator was used to excite NO molecules into a specific rotational level (Ji) in the X2II, Ω=1/2, ν=3 state. Laser-induced fluorescence (LIF) spectra of the (0,2) band of the A 2+ -X 2II1/2 system were then recorded at delays corresponding to a fraction of a collision. From the relative line intensities, rate coefficients were determined for transfer of the excited NO molecule from the level X 2II1/2, ν = 3, Ji to different final rotational levels (Jf) in the X 2II1/2, ν=2 state. Results are reported for Ji=3.5, 4.5, 7.5, 10.5, and 15.5. The data show a significant, though not strong, propensity for J to decrease by one; i.e., for ΔJ=Jf-Ji= -1, especially for the higher Ji levels. This result is interpreted as arising from a combination of (a) the tendency to minimize the energy that has to be accommodated in the relative translation of the collision partners, and (b) the favoring of ΔJ = ±1 changes when V- V intermolecular exchange occurs under the influence of dipole-dipole interactions.

Original languageEnglish
Pages (from-to)9296-9302
JournalJournal of Chemical Physics
Issue number20
Publication statusPublished - 22 Nov 1999

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