MBPT CALCULATIONS OF THE JAHN-TELLER AND SPIN-ORBIT SPLITTING AND SPIN HAMILTONIAN PARAMETERS OF METHOXY

$^{*}$National Research Council Research Associate $^{1}$G. D. Purvis and R. J. Bartlett, J. Chem. Phys. 68, 2114 (1978). $^{2}$M. Iwasaki and K. Toriyama, J. Am. Chem. Soc. 100, 1964 (1978).Author Institution:Methoxy ($CH_{3}O$) has a degenerate ground state In $C_{3}v$ symmetry. In accordance with the Jahn-Teller theorem, this radical distorts to a $C_{S}$ Symmetry where it lies a nondegenerate ground state. The degenerate energy levels are also split by spin-orbit coupling. The Jahn-Teller distortions caused by the coupling of three e-vibrational modes have been calculated using the many-body perturbation theory developed by Bartlett and $Purvis^{1}$. The results of these calculations show that in the case of methoxy the coupling of the vibrational modes is important for calculating the energy lowering caused by the distortion. Using only the dominant vibrational mode yields an energy lowering of 0.23 kcal/mole whereas coupling the modes together yields a lowering of 0.64 kcal/mole. Methoxy has recently been detected by its electron spin resonance (ESR) $signal^{2}$. The spin-orbit coupling, the g tensor, and the hyperfine tensor have been calculated from the self-consistent-field wavefunction and compared with the ESR results. The spin-orbit coupling results in a further energy lowering of 0.11 kcal/mole