Direct observation of bimolecular reactions of ultracold KRb molecules

• Published in: Science (American Association for the Advancement of Science) Vol. 366; no. 6469; pp. 1111 - 1115
• Main Authors: Hu, M-G, Liu, Y, Grimes, D D, Lin, Y-W, Gheorghe, A H, Vexiau, R, Bouloufa-Maafa, N, Dulieu, O, Rosenband, T, Ni, K-K
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 29-11-2019; American Association for the Advancement of Science (AAAS); AAAS
• Subjects: Chemical reactions; Diatomic molecules; Femtochemistry; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Intermediates; Ionization; Mass spectrometry; Mass spectroscopy; Observation; Organic chemistry; Physics; Potassium; Quantum Physics; Rubidium; Velocity
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.aay9531

Femtochemistry techniques have been instrumental in accessing the short time scales necessary to probe transient intermediates in chemical reactions. In this study, we took the contrasting approach of prolonging the lifetime of an intermediate by preparing reactant molecules in their lowest rovibronic quantum state at ultralow temperatures, thereby markedly reducing the number of exit channels accessible upon their mutual collision. Using ionization spectroscopy and velocity-map imaging of a trapped gas of potassium-rubidium (KRb) molecules at a temperature of 500 nanokelvin, we directly observed reactants, intermediates, and products of the reaction
K
Rb +
K
Rb → K
Rb
* → K
+ Rb
Beyond observation of a long-lived, energy-rich intermediate complex, this technique opens the door to further studies of quantum-state-resolved reaction dynamics in the ultracold regime.