Low-Energy Collisions of Zeeman-Decelerated NH Radicals with He Atoms

Abstract

We report an experimental study of state-to-state inelastic scattering of NH (X 3 Σ − , N = 0, j = 1) radicals with He atoms. Using a crossed molecular beam apparatus that combines a Zeeman decelerator and velocity map imaging, we study both integral and differential cross sections in the N = 0, j = 1 → N = 2, j = 3 inelastic channel. We developed various new REMPI schemes to state-selectively detect NH radicals, and tested their performance in terms of sensitivity and ion recoil velocity. We found a 1 + 2′ + 1′ REMPI scheme using the A 3 Π ← X 3 Σ − resonant transition, which yields acceptable recoil velocities and is more than an order of magnitude more sensitive than conventional onecolor REMPI schemes to detect NH. We used this REMPI scheme to probe state-to-state integral and differential cross sections around the channel opening at 97.7 cm −1 , as well as at higher energies where structure in the scattering images could be resolved. The experimental results are in excellent agreement with the predictions from quantum scattering calculations which are based on an ab initio NH-He potential energy surface.

High-Resolution Imaging of C + He Collisions using Zeeman Deceleration and Vacuum-Ultraviolet Detection

“…Thus, the number of systems for which the full potential of this approach could be exploited remained limited. The recent demonstration of Zeeman deceleration in crossed beam scattering experiments employing VMI, 23,24 and in particular the combination with recoil-free vacuum ultraviolet (VUV) based REMPI detection, 25 has alleviated these restrictions.…”

Cold Chemistry

“…The contribution by Plomp et al. demonstrates the power of cold beams, achieved by Zeeman deceleration and accompanied by improved Resonance Enhanced Mulitphoton Ionization detection, to probe differential scattering of state-to-state excitation of NH colliding with helium . These detailed cross sections, challenging to measure in any other way, are in excellent agreement with calculations.…”

Imaging Resonance Effects in C + H2 Collisions Using a Zeeman Decelerator

“…Thus, the number of systems for which the full potential of this approach could be exploited remained limited. The recent demonstration of Zeeman deceleration in crossed-beam scattering experiments employing VMI, , and in particular the combination with recoil-free vacuum ultraviolet (VUV) based REMPI detection, has alleviated these restrictions.…”