Neon and argon matrix ESR and theoretical studies of the (CH3Cd)-C-12, (CD3Cd)-C-12, (CH3Cd)-C-13, (CH3)-C-12 Cd-111, and (CH3)-C-12 Cd-113 radicals

Electron spin resonance (ESR) studies are reported for the first time on th e various isotopomers of the CH3Cd radical isolated in neon and argon matri ces. The radicals were generated in neon matrices by the reaction of laser- ablated cadmium metal and various methyl precursors, and in argon matrices by x-irradiation. The neon matrix values measured were g(perpendicular to)= 1.9491(1), A(perpendicular to)(H)=17.0(1) MHz, A(perpendicular to)(D)=2.6(1 ) MHz, A(perpendicular to)(C-13)=163(3) MHz, and A(perpendicular to)(Cd-111 )=-3083(3) MHz, and estimates were derived for A(parallel to)(C-13)=230(50) MHz and A(parallel to)(Cd-111)=-3486(5) MHz. The argon matrix values measu red were g(perpendicular to)=1.952(1), A(perpendicular to)(H)=16(1) MHz and A(perpendicular to)(Cd-111)=3301(3) MHz, and an estimate was derived for A (parallel to)(Cd-111)=-3704(5) MHz. The ESR experimental A(dip)(Cd-111) val ues for the neon and the argon matrices agree with the reported gas-phase v alue [J. Chem. Phys. 101, 6396 (1994)]. The matrix ESR A(iso)(Cd-111) value s show small shifts compared with the gas-phase results (5% greater for the neon matrix and 12% greater for the argon matrix). At 4.3 K in the neon ma trices, additional ESR lines assigned to tunneling phenomena were observed. The radical geometry obtained from ab initio calculations was consistent w ith that reported from the various experimental results. Multireference sin gle and double excitation configuration interaction (MRSDCI) calculations o f the hyperfine interactions gave values that were consistently below the e xperimental values of A(iso) and A(dip) for Cd-111, H, and C-13. MRSDCI cal culations for the CdH radical showed an analogous trend. (C) 1999 American Institute of Physics. [S0021-9606(99)00507-3].