Correlations in rotational energy transfer for NO-D inelastic collisions.

We present a combined experimental and theoretical study of state-to-state inelastic collisions between NO (X Π, j = 1/2, f) radicals and D (j = 0, 1, 2, 3) molecules at collision energies of 100 cm and 750 cm. 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 D are observed. De-excitation of D 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-D potential energy surfaces. The observed trends in the correlated scattering cross sections are understood in terms of the NO-D quadrupole-quadrupole interaction.