Associative detachment of rubidium hydroxide

Abstract

We performed calculations of the optimized structure, harmonic vibrational frequencies and dissociation energies of RbOH and its anion, and investigate the interactions between Rb and OH$^-$ leading to possible associative detachment pathways. The electron affinity of RbOH was computed to be 0.2890 eV, with a bond energy of Rb+OH$^-$ half that of Rb+OH. To determine other possible charge loss pathways, the Rb+OH and Rb+OH$^-$ dissociation curves were computed using couple cluster methods along all possible collisional angles. An adiabatic curve crossing between the neutral and charged molecule was found at the inner wall of the molecular potential curve for linear geometries. Associative detachment rates were estimated using the Langevin ion capture cross-section for hydroxide. We find for $v\ge 2$ an associative detachment rate of $>2\times 10^{-9}$ cm$^3$s$^{-1}$, while for $v=0$ and 1 no appreciable rate exists. This strong dependence on vibrational level suggests the ability to control the associative detachment rate directly

Ab initio study of the neutral and anionic alkali and alkaline earth hydroxides: Electronic structure and prospects for sympathetic cooling of OH−

“…These conclusions support the general idea that anions with higher EA are more stable against detachment process. As was shown for Rb hydroxide 39,41 , the crossing point occurs higher in energy for larger θ values. This is also true for the other hydroxides.…”

“…The feasibility of sympathetic cooling of OH − using ultracold Rb atoms has been studied by theoretical methods [38][39][40][41] and is currently under experimental investigation using an ion-atom hybrid trap. The first experimental results 49 have shown a loss of OH − from the trap, which was attributed to the associative detachment (AD) reaction Rb+OH − → RbOH+e − .…”

“…Moreover, they all exhibit a low energy bending degree of freedom, making the compounds «floppy» upon the bending motion. On the other hand, no information exist on their anion counterparts, with the exception of RbOH − for which several theoretical studies have been performed in the context of cold chemistry [38][39][40][41] .…”

Computing rotational energy transfers of OD−/OH−in collisions with Rb: isotopic effects and inelastic rates at cold ion-trap conditions

“…RbOH e 11 ( ) +  + -which has been estimated to be exothermic by 1.4 eV [25,26]. However, recent model calculations regarding the above process [27] suggested that the AD channels would be open only if the OH − ions in the trap were vibrationally excited to v 2,  since no appreciable AD rate coefficients were found for vibrationally colder molecules. However, given the fairly simple modelling of the AD kinetics discussed in that work [27], the question of the actual role of the process of (11) in the existing experiments still remains to be answered and further calculations would be needed to settle its mechanism and its efficiency under trap conditions.…”

“…However, recent model calculations regarding the above process [27] suggested that the AD channels would be open only if the OH − ions in the trap were vibrationally excited to v 2,  since no appreciable AD rate coefficients were found for vibrationally colder molecules. However, given the fairly simple modelling of the AD kinetics discussed in that work [27], the question of the actual role of the process of (11) in the existing experiments still remains to be answered and further calculations would be needed to settle its mechanism and its efficiency under trap conditions. At the present stage, therefore, our results do not include the AD channels in the rate calculations since we assume, from what stated by the experiments, that all molecular anions populate the ground vibrational level and therefore the AD process is probably still closed.…”