Mapping partial wave dynamics in scattering resonances by rotational de-excitation collisions

TL;DR

This study investigates how individual quantum partial waves evolve during low-energy NO–He collisions at scattering resonances, revealing detailed dynamics through rotational de-excitation measurements.

Contribution

It introduces a method to probe partial wave dynamics in quantum scattering by using rotational de-excitation collisions at resonances, providing detailed insight into angular momentum evolution.

Findings

Distinct partial wave fingerprints observed in differential cross sections

Rotational de-excitation probes time-reversed excitation with high resolution

Enhanced understanding of quantum scattering dynamics at low energies

Abstract

One of the most important parameters in a collision is the 'miss distance' or impact parameter, which in quantum mechanics is described by quantized partial waves. Usually, the collision outcome is the result of unavoidable averaging over many partial waves. Here we present a study of low-energy NO\textendash He collisions, that enables us to probe how individual partial waves evolve during the collision. By tuning the collision energies to scattering resonances between 0.4 and 6 cm$^{-1}$, the initial conditions are characterized by a limited set of partial waves. By preparing NO in a rotationally excited state before the collision and by studying rotational de-excitation collisions, we were able to add one quantum of angular momentum to the system and trace how it evolves. Distinct fingerprints in the differential cross sections yield a comprehensive picture of the partial wave dynamics during the scattering process. Exploiting the principle of detailed balance, we show that rotational de-excitation collisions probe time-reversed excitation processes with superior energy and angular resolution.