Ab initio-CI study of MgCH3 radical: analysis of the Jahn-Teller effect inthe first excited state

Ab initio structural and vibrational calculations have been performed on th e ground state and first excited state of the methylmagnesium radical. The vertical transitions calculated with the configuration interaction enable t he low-lying states to be described The first excited state has E symmetry and is predominantly Rydberg. The relaxation of this C-3v structure leads t o two C-s A' and A" structures. The energy stabilization by Jahn-Teller eff ect is very small (16 cm(-1) for A' structure and 21 cm(-1) for Al one) and the largest deformations affect the HCMg angles. The potential energy surf ace, calculated near the Jahn-Teller point, is very similar to the well-kno wn CH3O radical one. (C) 2000 Elsevier Science B.V. All rights reserved.