Precision test of statistical dynamics with state-to-state ultracold chemistry

Yu Liu; Ming-Guang Hu; Matthew A Nichols; Dongzheng Yang; Daiqian Xie; Hua Guo; Kang-Kuen Ni

doi:10.1038/s41586-021-03459-6

Precision test of statistical dynamics with state-to-state ultracold chemistry

Nature. 2021 May;593(7859):379-384. doi: 10.1038/s41586-021-03459-6. Epub 2021 May 19.

Authors

Yu Liu^#^{1

2

3

4}, Ming-Guang Hu^#^{5

6

7}, Matthew A Nichols^{5

6

7}, Dongzheng Yang⁸, Daiqian Xie⁸, Hua Guo⁹, Kang-Kuen Ni^{10

11

12}

Affiliations

¹ Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA. yu.liu-1@colorado.edu.
² Department of Physics, Harvard University, Cambridge, MA, USA. yu.liu-1@colorado.edu.
³ Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA. yu.liu-1@colorado.edu.
⁴ Time and Frequency Division, National Institute of Standards and Technology, Boulder, CO, USA. yu.liu-1@colorado.edu.
⁵ Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
⁶ Department of Physics, Harvard University, Cambridge, MA, USA.
⁷ Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA.
⁸ Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China.
⁹ Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, USA.
¹⁰ Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA. ni@chemistry.harvard.edu.
¹¹ Department of Physics, Harvard University, Cambridge, MA, USA. ni@chemistry.harvard.edu.
¹² Harvard-MIT Center for Ultracold Atoms, Cambridge, MA, USA. ni@chemistry.harvard.edu.

^# Contributed equally.

PMID: 34012086
DOI: 10.1038/s41586-021-03459-6

Abstract

Chemical reactions represent a class of quantum problems that challenge both the current theoretical understanding and computational capabilities¹. Reactions that occur at ultralow temperatures provide an ideal testing ground for quantum chemistry and scattering theories, because they can be experimentally studied with unprecedented control², yet display dynamics that are highly complex³. Here we report the full product state distribution for the reaction 2KRb → K₂ + Rb₂. Ultracold preparation of the reactants allows us complete control over their initial quantum degrees of freedom, whereas state-resolved, coincident detection of both products enables the probability of scattering into each of the 57 allowed rotational state-pairs to be measured. Our results show an overall agreement with a state-counting model based on statistical theory^4-6, but also reveal several deviating state-pairs. In particular, we observe a strong suppression of population in the state-pair closest to the exoergicity limit as a result of the long-range potential inhibiting the escape of products. The completeness of our measurements provides a benchmark for quantum dynamics calculations beyond the current state of the art.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't