Correlations in rotational energy transfer for NO–D2 inelastic collisions
Guoqiang Tang, Matthieu Besemer, Tim de Jongh, Quan Shuai, Ad van der Avoird, Gerrit C. Groenenboom, Sebastiaan Y. T. van de Meerakker
Abstract
We present a combined experimental and theoretical study of state-to-state inelastic collisions between NO (X 2Π1/2, j = 1/2, f) radicals and D2 (j = 0, 1, 2, 3) molecules at collision energies of 100 cm−1 and 750 cm−1. Using the combination of Stark deceleration and velocity map imaging, we fully resolve pair-correlated excitations in the scattered molecules. Both spin–orbit conserving and spin–orbit changing transitions in the NO radical are measured, while the coincident rotational excitation (j = 0 → j = 2) and rotational de-excitation (j = 2 → j = 0 and j = 3 → j = 1) in D2 are observed. De-excitation of D2 shows a strong dependence on the spin–orbit excitation of NO. We observe translation-to-rotation energy transfer as well as direct rotation-to-rotation energy transfer at the lowest collision energy probed. The experimental results are in good agreement with cross sections obtained from quantum coupled-channels calculations based on recent NO–D2 potential energy surfaces. The observed trends in the correlated scattering cross sections are understood in terms of the NO–D2 quadrupole–quadrupole interaction.