Spectroscopic properties of the molecular ions BeX⁺ (X=Na, K, Rb): forming cold molecular ions from an ion–atom mixture by stimulated Raman adiabatic process

Abstract

In this theoretical work, we calculate potential energy curves, spectroscopic parameters and transition dipole moments of molecular ions BeX + (X=Na, K, Rb) composed of alkaline ion Be and alkali atom X with a quantum chemistry approach based on the pseudopotential model, Gaussian basis sets, effective core polarization potentials, and full configuration interaction (CI). We study in detail collisions of the alkaline ion and alkali atom in quantum regime. Besides, we study the possibility of the formation of molecular ions from the ion-atom colliding systems by stimulated Raman adiabatic process and discuss the parameters regime under which the population transfer is feasible. Our results are important for ion-atom cold collisions and experimental realization of cold molecular ion formation.

Electronic structure, cold ion–atom elastic collision properties and possibility of laser cooling of BeCs+ molecular ion

“…For the remaining states 3 1 S + , 5 1 S + and 7 1 S + dissociating into Be + + Cs, we note significant negative permanent dipole moments in a particular region yield the same linear behavior at large distances, showing the increasing distance between the negative and positive center-of-charge. This behavior is typically observed for heteronuclear molecular ions, [34][35][36][37][38][39][40] and implies that even molecular ions in very weakly bound states have effectively a significant permanent electric dipole moment. For the permanent dipole moments of the of 3 S + , 1,3 P and 1,3 D electronic states, we get the same observation as for the permanent dipole moments of the 1 S + states.…”

“…This state correlates at large distances to a ground-state neutral Be atom and a closed-shell alkali-metal Cs + ion similarly to the (Be-Alk) + ionic systems. 38,40 Unlike the alkaline-earth ionic systems, the first excited state of symmetry 1 S + , for the BeCs + molecular ion, is correlated to a first excitedstate neutral alkaline-earth atom ( 3 P) and a closed-shell alkalimetal ion due to the properties of the Cs atom. This state is quite close to the next state, 3 1 S + , and maintains an energy gap of about 321.75 cm À1 at the internuclear distance R = 200 bohr.…”

“…In addition, we compare our results for the BeCs + ground state with those of (Be-Alk) + reported in previous work. 34,38,40 Indeed, the well depth of the ground state decreases with the mass of the alkali atoms. Thus, the smallest D e is for BeCs + (1511 cm À1 ) and the largest one is for the BeLi + (4862 cm À1 ), 34 while the band lengths of the ground state systematically decrease with the increasing atomic number of the alkalimetal atoms from 4.94 bohr for BeLi + 34 to 7.11 bohr for BeCs + .…”

Cold hybrid ion-atom systems

“…where the expressions in round brackets are 3j symbols, 2S+1 L||Q 2(4) || 2S+1 L is the reduced matrix element of the quadrupole (hexadecapole) moment, and α 0 (iω) and α 2 (iω) are the scalar and tensor components of the dynamic electric dipole polarizability at imaginary frequency of the atom in the 2S+1 L state. The electronic structure data, including the potential energy curves for the ground and excited electronic states, transition electric dipole moments, and matrix elements of the spin-orbit coupling have been calculated for several ion-atom systems relevant for ongoing experimental efforts: (Na+Ca) + (Gacesa et al, 2016;Makarov et al, 2003), (Rb+Ba) + (Knecht et al, 2010;Krych et al, 2011), (Li/Na/K/Rb/Cs+Sr) + , (Rb+Ca) + (Belyaev et al, 2012;Tacconi et al, 2011), (Rb+Yb) + (Lamb et al, 2012;McLaughlin et al, 2014;Sayfutyarova et al, 2013), (Li+Yb) + da Silva Jr et al, 2015;Tomza et al, 2015), (Ca/Sr/Ba/Yb+Cr) + (Tomza, 2015), (Li+Be) + (Ghanmi et al, 2017), (Li+Mg) + (ElOualhazi and , (Li+Ca) + (Saito et al, 2017), (Li+Sr) + (Jellali et al, 2016), (Rb+Ca/Sr/Ba/Yb) + (da Silva Jr et al, 2015), (Na/Ka/Rb+Be) + (Ladjimi et al, 2018), (Li+Li) + (Bouchelaghem and Bouledroua, 2014;Bouzouita et al, 2006;Musia l et al, 2015), (Na+Na) + (Berriche, 2013;Bewicz et al, 2017), (K+K) + (Skupin et al, 2017), (Rb+Rb) + (Jraij et al, 2003;Jyothi et al, 2016), (Cs+Cs) + (Jamieson et al, 2009;Jraij et al, 2005), (Li+Na) + (Li et al, 2015;Musia l et al, 2018), (Li+K) + (Berriche et al, 2005;…”

Characterization of the electronic ground state of Mg$_2^+$ by PFI-ZEKE photoelectron spectroscopy

“…Most of what is known on this ion was obtained in highlevel ab initio calculations [5,[26][27][28][29][30][31]. The development of hybrid ion-atom traps, accommodating both ultracold atomic gases and trapped ions (see, e.g., Refs.…”