Actualités du Laboratoire

we present an overview of two-layer anharmonicity in water dimer and in hydrogen molecule confined in clathrates

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.

To test the hypothesis that amino acids, the molecular precursors of life, could have reached primitive Earth embedded in icy grains of space transported by comets or asteroids, we are combining a DFT study of the decarboxylation and deamination of glycine—neutral, singly, and doubly ionized—with a RT-TDDFT study of the same neutral and charged glycine interacting with ionizing radiation. In all cases, the molecules are surrounded by water molecules, mimicking the icy environment. The outcomes of this study will be presented.