Global Full-Dimensional Potential Energy Surface for the Reaction 23Na87Rb + 23Na87Rb → 23Na2 + 87Rb2 and the Formation Rate and Lifetime of the 23Na287Rb2 Collision Complex

J Phys Chem A. 2022 Nov 23. doi: 10.1021/acs.jpca.2c06438. Online ahead of print.

ABSTRACT

A full-dimensional global potential energy surface (PES) for the reaction ²³Na⁸⁷Rb + ²³Na⁸⁷Rb → ²³Na₂ + ⁸⁷Rb₂ was constructed based on high-level ab initio calculations. The short-range part was expressed as a permutation invariant polynomial-neural network (PIP-NN) fit of 22 003 ab initio points calculated using a coupled cluster method with the one-electron basis 5s5p5d2f plus effective core potentials and core polarizability potentials, while the long-range part was represented in an asymptotically correct form based on multipole expansion. The formation rate of the ²³Na₂⁸⁷Rb₂ complex calculated using a quantum statistical method is in good agreement with experiment, while the estimated 19.20 μs lifetime of the complex from Rice-Ramsperger-Kassel-Marcus (RRKM) theory is significantly shorter than the measured millisecond decay rate, signaling either the inadequacy of RRKM theory or a yet unresolved loss mechanism.

PMID:36417561 | DOI:10.1021/acs.jpca.2c06438