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

Ab initio structural and vibrational calculations have been performed on the ground state and first excited state of the methylmagnesium radical. The vertical transitions calculated with the configuration interaction enable the 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 to two C-s A' and A" structures. The energy stabilization by Jahn-Teller effect 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 surface, calculated near the Jahn-Teller point, is very similar to the well-known CH3O radical one. (C) 2000 Elsevier Science B.V. All rights reserved.