Service de Chimie Quantique et Photophysique (CQP), Université libre de Bruxelles (ULB), Brussels, Belgium.
J Chem Phys. 2017 May 21;146(19):194309. doi: 10.1063/1.4983627.
We have performed a systematic ab initio study on alkali and alkaline earth hydroxide neutral (MOH) and anionic (MOH) species where M = Li, Na, K, Rb, Cs or Be, Mg, Ca, Sr, Ba. The CCSD(T) method with extended basis sets and Dirac-Fock relativistic effective core potentials for the heavier atoms has been used to study their equilibrium geometries, interaction energies, electron affinities, electric dipole moment, and potential energy surfaces. All neutral and anionic species exhibit a linear shape with the exception of BeOH, BeOH, and MgOH, for which the equilibrium structure is found to be bent. Our analysis shows that the alkaline earth hydroxide anions are valence-bound whereas the alkali hydroxide anions are dipole bound. In the context of sympathetic cooling of OH by collision with ultracold alkali and alkaline earth atoms, we investigate the 2D MOH potential energy surfaces and the associative detachment reaction M + OH→- MOH + e, which is the only energetically allowed reactive channel in the cold regime. We discuss the implication for the sympathetic cooling of OH and conclude that Li and K are the best candidates for an ultracold buffer gas.
我们对碱金属和碱土金属氢氧化物中性（MOH）和阴离子（MOH）物种（其中 M = Li、Na、K、Rb、Cs 或 Be、Mg、Ca、Sr、Ba）进行了系统的从头算研究。使用包含扩展基组和较重原子的狄拉克-福克相对论有效核势的 CCSD(T)方法来研究它们的平衡几何形状、相互作用能、电子亲和能、电偶极矩和势能面。除了 BeOH、BeOH 和 MgOH，所有中性和阴离子物种都呈现线性形状，对于后两者，发现其平衡结构为弯曲。我们的分析表明，碱土金属氢氧化物阴离子是价态结合的，而碱金属氢氧化物阴离子是偶极结合的。在通过与超冷碱金属和碱土原子碰撞来冷却 OH 的背景下，我们研究了二维 MOH 势能面和缔合脱附反应 M + OH→- MOH + e，这是低温下唯一允许的反应通道。我们讨论了对 OH 的 sympathetic 冷却的影响，并得出结论 Li 和 K 是超冷缓冲气体的最佳候选者。
