Resonances and bound rovibrational levels in the interacting X, A, C, and D states of HeH, HeD, 3HeH, and 3HeD

Charge transfer in sodium iodide collisions

Sodium iodide (NaI) has, over the years, served as a prototype system in studies of non-adiabatic dynamics. Here, the charge transfer collision reactions Na⁺ + I^- ⇆ Na + I (mutual neutralization and ion-pair formation) are studied using an ab initio approach and the total and differential cross sections are calculated for the reactions. This involves electronic structure calculations on NaI to obtain adiabatic potential energy curves, non-adiabatic and spin-orbit couplings, followed by nuclear dynamics, treated fully quantum mechanically in a strictly diabatic representation. A single avoided crossing at 13.22 a₀ dominates the reactions, and the total cross sections are well captured by the semi-classical Landau-Zener model. Compared to the measured ion-pair formation cross section, the calculated cross section is about a factor of two smaller, and the overall shape of the calculated differential cross section is in reasonable agreement with the measured ion-pair formation differential cross section. Treating the Landau-Zener coupling as an empirical parameter of 0.05 eV, the measured total and differential cross sections are well captured when performing fully quantum mechanical cross section calculations including rotational coupling. A semi-empirical spin-orbit coupling model is also investigated, giving satisfactory estimation of the effects of spin-orbit interactions for the reactions.

Spectroscopic properties of the low-lying states of the HeH radical

Four lowest electronic states (X2Σ+, A2Σ+, B2Π and C2Σ+) of the HeH radical are investigated by performing high-precision ab initio calculations. Potential energy curves of HeH are calculated using the internally contracted multireference configuration interaction method in combination with the basis set of aug-cc-pV6Z. To improve the accuracy, additional Rydberg basis functions and the Pople correction are included in the calculations. The spectral parameters are evaluated and compared with literature data. The spin-orbit coupling effect of B2Π is taken into account by using the Breit-Pauli operator. Transition dipole moments between those four electronic states are also derived to obtain their emission spectra and radiative lifetimes. Radiative and predissociation lifetimes of several vibrational levels are also calculated, including the bound-continuum and bound-bound systems. Especially, the predissociation lifetimes are elaborated in detail. The results are in good agreement with the reported ones. Additionally, the emission spectra of bound A2Σ+, B2Π and C2Σ+ states to continuum X2Σ+ state are simulated at different temperatures.