RELATIVISTIC JAHN-TELLER EFFECTS IN THE QUARTET STATES OF K$_3$ AND RB$_{3}$: A VIBRATIONAL ANALYSIS OF THE 2$^4$E$^{\prime}\leftarrow{}$1$^4$A$_2^{\prime}$ ELECTRONIC TRANSITIONS BASED ON AB INITIO CALCULATIONS

Abstract

We apply the Multireference Rayleigh Schrodinger Perturbation Theory of second order to obtain the adiabatic potential energy surface of the 1$^4$A$_2^{\prime}$ electronic groundstate and the 2$^4$E$^{\prime}$ excited state of K$_3$ and Rb$_3$. Both trimers show a typical E$\times{}$e Jahn-Teller distortion in their 2$^4$E$^{\prime}$ state, which is analyzed in terms of the relativistic Jahn-Teller effect theory. Linear, quadratic as well as spin-orbit coupling terms are extracted from the \emph{ab initio} results and used to obtain theoretical spectra for a direct comparison to laser-induced fluorescence and magnetic circular dichroism spectra of alkali-doped helium nanodroplets [Aubock et al. J. Chem Phys. \textbf{129} 114501 (2008)].