Study on Quantum Dynamics of the Na + Na₂ Exchanged Reaction and Lifetime Prediction of Na₃ Complex Based on the Neural Network Potential Energy Surface

A high-precision global potential energy surface (PES) is constructed for the Na₃ system based on high-level <i>ab initio</i> calculations and the fundamental invariant neural network (FI-NN) method. The root-mean-square error (RMSE) of the PES is 2.88 cm^-1. The state-resolved quantum dynamics of the ground-state Na + Na₂ (<i>v</i> = 0, <i>j</i> = 0) → Na₂ (<i>v</i>', <i>j</i>') + Na reaction is studied using the time-dependent wave packet (TDWP) method on the new PES. Analysis of the relevant integral cross sections revealed a complicated energy-transfer mechanism during collisions. Similarly, the characteristics of the differential cross sections indicate that the complex-forming mechanism plays a dominant role in the reaction, providing conditions for a comprehensive exploration of the lifetimes of the complexes. Based on the Rice-Ramsperger-Kassel-Marcus (RRKM) theory, the calculated lifetime of the Na₃ complex is approximately 3.9 ns.