Probing ultracold chemistry using ion spectrometry

TL;DR

This paper introduces an advanced experimental setup combining ultracold molecule production with ion spectrometry to study ultracold chemical reactions, enabling direct observation of reaction intermediates and products.

Contribution

It presents a novel apparatus integrating quantum-state-selected ultracold molecules with ion spectrometry, facilitating detailed ultracold reaction analysis.

Findings

Direct observation of KRb + KRb reaction intermediates and products.

Calibration scheme for ion kinetic energy spectrometer at low energies.

Potential for future quantum state detection of reaction products.

Abstract

Rapid progress in atomic, molecular, and optical (AMO) physics techniques enabled the creation of ultracold samples of molecular species and opened opportunities to explore chemistry in the ultralow temperature regime. In particular, both the external and internal quantum degrees of freedom of the reactant atoms and molecules are controlled, allowing studies that explored the role of the long range potential in ultracold reactions. The kinetics of these reactions have typically been determined using the loss of reactants as proxies. To extend such studies into the short-range, we developed an experimental apparatus that combines the production of quantum-state-selected ultracold KRb molecules with ion mass and kinetic energy spectrometry, and directly observed KRb + KRb reaction intermediates and products [Science, 2019, 366, 1111]. Here, we present the apparatus in detail. For future studies that aim for detecting the quantum states of the reaction products, we demonstrate a photodissociation based scheme to calibrate the ion kinetic energy spectrometer at low energies.