High-Resolution Imaging of Velocity-Controlled Molecular Collisions Using Counterpropagating Beams

Abstract

We present ultrahigh-resolution measurements of state-to-state inelastic differential cross sections for NO-Ne and NO-Ar collisions, obtained by combining the Stark deceleration and velocity map imaging techniques. We show that for counterpropagating crossed beam geometries, the effect of the velocity spreads of the reagent beams on the angular resolution of the images is minimized. Furthermore, the counterpropagating geometry results in images that are symmetric with respect to the relative velocity vector. This allows for the use of inverse Abel transformation methods that enhance the resolution further. State-resolved diffraction oscillations in the differential cross sections are measured with an angular resolution approaching 0.3°. Distinct structures observed in the cross sections gauge the quality of recent ab initio potential energy surfaces for NO-rare-gas atom collisions with unprecedented precision.

Rotationally inelastic scattering of ND3with H2as a probe of the intermolecular potential energy surface

“…Low energy collisions of NH3 with He were studied theoretically by Gubbels et al [24] with a focus on the observation of scattering resonances and revealed diffraction oscillations in the small-angle scattering regions of the DCSs. These types of interference structures are beyond the resolution of the current experiments, but can in principle be resolved using a Stark decelerated molecular beam, as shown recently for inelastic collisions of NO with He, Ne and Ar [25,26].…”

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

“…Results were found to be in excellent agreement with quantum closecoupling calculations on coupled PESs for these radicalradical systems. In a subsequent study, Vogels et al 115 reported ultrahigh-resolution measurements of differential cross sections for state-to-state inelastic transitions in Stark decelerated NO induced by Ne and Ar atoms. An angular resolution of 0.3 • was achieved for the differential cross section.…”

Rotational Orientation Effects in NO(X) + Ar Inelastic Collisions

“…Many of these studies have focused on determining the integral cross sections, 18,19 as well as lower order vector correlations such as the k-k ′ correlation, embodied in the differential cross section. 18,[20][21][22][23][24][25][26][27][28][29][30][31] Parity dependent effects have been observed in both the integral 19 and differential cross sections. [26][27][28][29][30][31] More recently, the collision-induced alignment in the NO(X) + Ar system has been investigated experimentally 4,32 and theoretically, 3 and the classical kinematic apse model was found to largely explain the observed rotational alignment.…”