On the use of stereodynamical effects to control cold chemical reactions: the H + D$_{2}\longleftrightarrow$ D + HD case study

TL;DR

This study uses quantum calculations to demonstrate how stereodynamic control of molecular alignment can significantly influence the outcome of cold chemical reactions, enabling the reaction to be turned on or off.

Contribution

The paper generalizes previous experimental methods by providing a theoretical framework for stereodynamic control of reactions through molecular alignment at very low temperatures.

Findings

Significant control over reaction outcomes demonstrated

Reaction can be turned on or off with molecular state preparation

Multiple scenarios for optimizing reaction control identified

Abstract

Quantum calculations are reported for the stereodynamic control of the H + D$_{2}\longleftrightarrow$ D + HD chemical reaction in the energy range of 1-50 K. Stereodynamic control is achieved by a formalism similar to that reported by Perreault et al. [Nature Chem. 10, 561 (2018)] in recent experimental works in which the alignment of the molecular bond axis relative to the incident relative velocity is controlled by selective preparations of the molecule in a specific or superposition of magnetic projection quantum numbers of the initial molecular rotational level. The approach presented here generalizes the experimental scheme of Perreault et al. and offers additional degree of control through various experimental preparation of the molecular alignment angle. Illustrative results presented for the H + D$_{2}$ and D + HD reactions show significant control with the possibility of turning the reaction completely on or off with appropriate stereodynamic preparation of the molecular state. Various scenarios for maximizing and minimizing the reaction outcomes are identified with selective preparation of molecular rotational states.