Atomic data on inelastic processes in low-energy beryllium-hydrogen collisions

Abstract

Aims. Inelastic processes in low-energy Be + H and Be + + H − collisions are treated for the states from the ground and up to the ionic state with the aim to provide rate coefficients needed for non-local thermodynamic equilibrium (non-LTE) modeling of beryllium spectra in cool stellar atmospheres. Methods. The electronic molecular structure is determined by using a recently proposed model quantum approach that is based on an asymptotic method. Nonadiabatic nuclear dynamics is treated by means of multichannel formulas, based on the Landau-Zener model for nonadiabatic transition probabilities. Results. The cross sections and the rate coefficients for inelastic processes in Be + H and Be + + H − collisions are calculated for all transitions between 13 low-lying covalent states plus the ionic state. It is shown that the highest rate coefficient values correspond to the mutual neutralization processes with the final states Be(2s3s 1 S), Be(2s3p 1,3 P), Be(2s3d 3 D). These processes, as well as some of the excitation, de-excitation and ion-pair formation processes, are likely to be important for non-LTE modeling.

Inelastic processes in collisions of lithium positive ions with hydrogen anions and atoms

“…The model asymptotic approach [17] allows one to describe long-range nonadiabatic regions due to ionic-covalent interactions. In this case, nonadiabatic regions are passed by the system in a particular order and one can use the quantum multichannel model [14,[23][24][25][26] in order to treat a nonadiabatic nuclear dynamics. This model is advantageous because it is analytical.…”

“…As described above, a nonadiabatic transition probability in each nonadiabatic region is calculated by means of the adiabatic-potential-based formula within the LandauZener model. The multichannel analytic formulae [26] are then used for computing an inelastic probability for each state-to-state transition. Finally, the inelastic cross sections and rate coefficients are calculated for all transitions between the scattering channels collected in Table 1.…”

“…A series of avoided crossings due to the ionic-covalent interactions is clearly seen. Landau-Zener parameters in each nonadiabatic region are determined using the adiabaticpotential-based formula [17,28] followed by calculations of nonadiabatic transition probabilities with the multichannel formula [24,26]. Inelastic cross sections and rate coefficients for the recombination processes due to the transitions between the states listed in Table 2 are then calculated as usual.…”

Estimating inelastic heavy-particle – hydrogen collision data

“…Two such approaches for nonadiabatic nuclear dynamics have been proposed: the quantum branching probability current method (Belyaev 2013a) and the quantum multichannel analytic approach (Belyaev 1993;Belyaev et al 2014;Yakovleva et al 2016). Both approaches are based on electronic structure calculations and the LandauZener model.…”

“…For electronic structure calculations, in addition to ab initio methods, the approximate methods have been used: the asymptotic method (Belyaev 2013a) and the Linear Combinations of Atomic Orbitals (LCAO) method (Barklem 2016b(Barklem , 2017). The quantum model approaches have been successfully applied to a number of chemical elements relevant to non-LTE modeling, such as Al, Si, Ca, Be, and Mn, A&A 608, A33 (2017) (Belyaev 2013b;Belyaev et al 2014Belyaev et al , 2016Yakovleva et al 2016;Barklem 2016bBarklem , 2017Belyaev & Voronov 2017).…”