# Stereodynamical control of a quantum scattering resonance in cold molecular collisions

## TL;DR

This paper demonstrates that the outcome of cold molecular collisions can be fully controlled by aligning the rotational angular momentum of molecules, effectively switching a key quantum resonance on or off.

## Contribution

It introduces a method to control quantum scattering resonances in cold molecular collisions through molecular alignment, a novel approach in collision dynamics.

## Key findings

- Resonance can be switched on or off by molecular alignment.
- Complete control over collision outcomes is achievable.
- Alignment affects the dominance of specific partial wave resonances.

## Abstract

Cold collisions of light molecules are often dominated by a single partial wave resonance. For the rotational quenching of HD(v=1,j=2) by collisions with ground state para-H2, the process is dominated by a single L=2 partial wave resonance centered around 0.1 K. Here, we show that this resonance can be switched on or off simply by appropriate alignment of the HD rotational angular momentum relative to the initial velocity vector, thereby enabling complete control of the collision outcome.