# Controlling rotational quenching rates in cold molecular collisions

## TL;DR

This paper demonstrates how the rotational quenching rates in cold molecular collisions can be controlled by adjusting the relative orientation of the molecules, with potential applications to similar systems.

## Contribution

It introduces a method to manipulate rotational quenching rates through molecular alignment, based on helicity considerations, in cold molecular collision systems.

## Key findings

- Quenching rate maximized when HD is aligned along the collision axis.
- Quenching rate minimized at the magic angle.
- Orientation control influences chemical process rates.

## Abstract

The relative orientation of colliding molecules plays a key role in determining the rates of chemical processes. Here we examine in detail a prototypical example: rotational quenching of HD in cold collisions with H2. We show that the rotational quenching rate from j=2 -> 0, in the v=1 vibrational level, can be maximized by aligning the HD along the collision axis and can be minimized by aligning the HD at the so called magic angle. This follows from quite general helicity considerations and suggests that quenching rates for other similar systems can also be controlled in this manner.