DOI: 10.1063/5.0233558
Abstract:

While the growing realization of the importance of long-range interactions is being demonstrated in cold and ultracold bimolecular collision experiments, their influence on one of the most critical ion-neutral reactions has been overlooked. Here, we address the non-Langevin abrupt decrease observed earlier in the low energy integral cross sections and rate coefficients of the astrochemically important H + HeH$^+$ $\rightarrow$ H$^+_2$ + He reaction. We attribute this to the presence of artificial barriers on existing potential energy surfaces (PESs). By incorporating precise long-range interaction terms, we introduce a new refined barrierless PES for the electronic ground state of HeH$_{2}^{+}$ reactive system, aligning closely with high level {\ab} electronic energies. Our findings, supported by various classical, quantum, and statistical methods, underscore the significance of long-range terms in accurately modeling reactive PESs. The low temperature rate coefficient on this new PES shows a substantial enhancement as compared to the previous results and aligns with Langevin behavior. This enhancement could affect noticeably the impact HeH$^{+}$ abundance prediction in early Universe condition.