Knowledge Bank

We apply the Multireference Rayleigh Schrodinger Perturbation Theory of second order to obtain the adiabatic potential energy surface of the 1$4$A electronic groundstate and the 2$4$E excited state of K$3$ and Rb$3$. Both trimers show a typical E$\times$e Jahn-Teller distortion in their 2$4$E 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)].