Bimolecular Chemistry in the Ultracold Regime

• Published in: Annual review of physical chemistry Vol. 73; no. 1; pp. 73 - 96
• Main Authors: Liu, Yu, Ni, Kang-Kuen
• Format: Journal Article
• Language: English
• Published: United States Annual Reviews 20-04-2022; Annual Reviews, Inc
• Subjects: Chemical reactions; Chemistry; dipolar interaction; long-lived intermediate complex; Low temperature; Mass spectrometry; Physical chemistry; Production methods; Rotational states; RRKM theory; Statistical models; statistical theory; ultracold chemistry; ultracold molecules; long-lived intermediate complex; RRKM theory; statistical theory; ultracold molecules; dipolar interaction; ultracold chemistry
• ISSN: 0066-426X; 1545-1593
• DOI: 10.1146/annurev-physchem-090419-043244

Advances in atomic, molecular, and optical physics techniques allowed the cooling of simple molecules down to the ultracold regime (
1 mK) and opened opportunities to study chemical reactions with unprecedented levels of control. This review covers recent developments in studying bimolecular chemistry at ultralow temperatures. We begin with a brief overview of methods for producing, manipulating, and detecting ultracold molecules. We then survey experimental works that exploit the controllability of ultracold molecules to probe and modify their long-range interactions. Further combining the use of physical chemistry techniques such as mass spectrometry and ion imaging significantly improved the detection of ultracold reactions and enabled explorations of their dynamics in the short range. We discuss a series of studies on the reaction KRb + KRb → K
2
+ Rb
2
initiated below 1 μK, including the direct observation of a long-lived complex, the demonstration of product rotational state control via conserved nuclear spins, and a test of the statistical model using the complete quantum state distribution of the products.