Experimental and theoretical study of the B(2)2Σ+→ X(1)2

Abstract

Spectral bands for the B(2) 2 Σ + → X(1) 2 Σ + electronic transition in the doublypolar open-shell KSr molecule are recorded at moderate resolution using the thermoluminescence technique. The spectra are simulated using three kinds of advanced electronic structure calculations, allowing for an assessment of their accuracy on one hand, and for the derivation of fundamental spectroscopic constants of the X(1) 2 Σ + KSr ground state and the excited electronic state B(2) 2 Σ + , on the other hand. These results should facilitate further studies aiming at creating ultracold bosonic or fermionic KSr molecules.

The RbSr2Σ+ground state investigatedviaspectroscopy of hot and ultracold molecules

“…This procedure is described in detail in ref. 18 These fitted Dunham coefficients allow for a new prediction of the vibrational level energies in the X(1) 2 Σ + and B(2) 2 Σ + states, followed by an assignment of additional band heads in the thermoluminescence spectrum. With the improved assignment a correction of Dunham coefficients becomes possible, and we repeat the whole procedure until the final identification of 24 band heads, whose energies are given in Table IV as a Deslandres table.…”

“…Intensities of all spectral lines are calculated assuming thermal equilibrium in the central part of the heat-pipe. The simulation procedure has been described in detail by Szczepkowski et al [18], including equations necessary to perform the calculations.…”

“…In the first step, we record thermoluminescence spectra using the method and experimental setup described in ref. 18. We therefore provide here only information specific to this paper.…”

“…Knowledge of these weakly-bound levels is sufficient to determine the long-range behaviour of the PECs [28,29]. Thermoluminescence and laser induced fluorescence (LIF) spectroscopy in high-temperature ovens provide spectra with many optical lines at a fraction of cm −1 precision [18,30,31]. Thermoluminescence and LIF spectra are usually dominated by the radiative decay towards the most bound levels of the ground-state potential and therefore allow to determine the behaviour of the PECs in a range of internuclear distances centred around the potential equilibrium distance.…”

“…In order to create molecules at ultracold temperatures and to understand quantum chemistry processes, an accurate molecular model is needed. Recently ab-initio calculations for alkali -alkaline-earth(-like) molecules have provided potential energy curves (PECs), permanent electric dipole moments and transition dipole moments, and a few attempts at benchmarking theories with experiments have been recorded [18][19][20][21][22][23][24]. The precision of ab-initio calculations is typically not enough to reliably predict the properties that need to be known to form ultracold molecules, such as molecular binding energies.…”