The Jahn–Teller effect in the 3 pe ′ Rydberg state of H 3 : review of experimental and ab initio determinations

The dissociative recombination (DR) of Hions with electrons, producing neutral atomic and molecular fragments, is driven primarily by the vibronic Jahn–Teller (JT) interaction between the electronic components of thepe ′ e− –Hcollision (Rydberg) channel. The JT parameters characterizing this interaction are therefore of great interest as they are required for the theoretical predictions of the DR cross section. In this contribution, we review various determinations of these quantities that have been made previously, based both on spectroscopic studies of 3pe ′ Rydberg-excited H3 states, and on the analysis of the correspondingab initio H3 Rydberg potential surfaces near the conical intersection (D3h symmetry) forn =3−5. The highly correlated theoretical 3pe ′ potential surfaces of Mistríket al. are used for a new determination of both the linear and quadratic JT terms.