Investigating the electronic properties and structural features of MgH and of MgH− anions

Abstract

In the present paper we analyze in detail several properties of the MgH − anion and the MgH neutral molecule using accurate ab initio quantum computational methods in order to establish with higher reliability specific molecular features like the gas-phase electron affinity (EA) , the Frank-Condon (FC) factors for excitation of the neutral and of its anion to their lower electronic states, and the general feasibility of employing the anion in photodetachment experiments after its confinement in cold ion traps. The calculations suggest that the EA value is in agreement with an existing early experiment and further places on it a smaller error bar than that given before.Accurate zero-point-energy (ZPE) corrections are also included in our calculations and their effects discussed.

Modeling Quantum Kinetics in Ion Traps: State‐changing Collisions for OH+() Ions with He as a Buffer Gas

“…One clearly sees from the relative energy spacings shown by Figure that the 0 transitions involve much larger energy gaps than those transitions were only the S quantum number changes: spin‐flip processes therefore involve much smaller energy transfers during inelastic collisions, as we shall further discuss below and as we have already illustrated in our earlier work . We also see in that same Figure that, by removing the spin‐rotational coupling which causes the energy splitting terms, we could obtain an approximate picture for the rotational structure of the target molecule that becomes essentially described as a pseudo‐ case, with the corresponding simplification of the energy spacings reported by the schematic energy ladder in the center of Figure .…”

“…A further topic of interest in studying the inelastic collisional dynamics of the present system is provided by searching for possible propensity rules that would allow us to calibrate the relative sizes of the state‐changing cross sections in the presence of the full couplings of the electronic spin and the rotational angular momenta, within the full angular momentum coupling dynamics. We have recently carried out such a study for this very system and have been able to computationally show the dominance of the pure spin‐changing collisional probabilities in relation to the other rotationally inelastic channels. In the present analysis, however, we shall extend the use of the quantum dynamics to further discuss the role of its computed rates within the master eq.s that analyse the temporal evolutions of the rotational state populations under a variety of conditions chosen to describe the ion trap and of which those discussed above have been an example.…”

“…The full calculations including the spin‐rotation angular momenta coupling effects have been recently reported (L. González‐Sánchez and R. Wester and F.A. Gianturco, Mol.Phys.2018, DOI 10.1080/00268976.2018.1442597) with the aim of extracting specific propensity rules controlling the size of the cross sections. The present study is instead directed to modelling trap cooling dynamics by further obtaining the solutions of the corresponding kinetics equations under different trap schemes so that, using the presently computed rates can allow us to indicate specific optimal conditions for the experimental setup of the collisional rotational cooling in an ion trap for the system under study.…”

Collisional Quantum Dynamics for MgH− (1Σ+) With He as a Buffer Gas: Ionic State-Changing Reactions in Cold Traps

“…If therefore becomes of direct interest from the above findings to further investigate polar molecular anions which could be employed for direct selective photo-detachment experiments and also modeled from quantum simulations of their structural and dynamical aspects. We have recently studied in detail the electronic properties of the MgH − (X 2 Σ + ) anion and of its corresponding neutral (González-Sánchez et al, 2017), MgH (X 2 Σ + ) with the aim of accurately assessing the adiabatic electron affinity (AEA) value of the anion, as well as which electronic states of both systems would become relevant during a photo-detachment experiment.…”

“…We have recently carried out, in fact, a detailed calculation comparing the electronic properties and structural features of the isolated MgH − anion and of its neutral counterpart, MgH (X 2 Σ + ), as the two main partners of a selective photo-detachment experiment (González-Sánchez et al, 2017). In order to further investigate the experimental preparation of MgH − molecules in specific rotational states, we now need to examine the dynamics of state-changing kinetics of MgH − in a cold ion trap and under the presence of He gas as a buffer gas uploaded in the cold trap (Hauser et al, 2015; Hernández Vera et al, 2018).…”