dc.creator Wadt, W. R. en_US dc.creator Moomaw, William R. en_US dc.date.accessioned 2006-06-15T13:18:27Z dc.date.available 2006-06-15T13:18:27Z dc.date.issued 1970 en_US dc.identifier 1970-D-5 en_US dc.identifier.uri http://hdl.handle.net/1811/8394 dc.description $^{1}$D. S. McClure, J. Chem. Phys. 20, 682 (1952)."" en_US dc.description Author Institution: Department of Chemistry, Williams College en_US dc.description.abstract Spin-orbit coupling in p-$\pi$ aromatic molecules is known to be extremely small. Transitions between the lowest $\pi, \pi^{*}$ triplet state and the ground state (T $<->$ $S_{\eta}$) are found to be very weak and largely polarized out of plane despite selection rules that would allow in-plane polarized intensity. Within the framework of LCAO-MO approximations it has been shown by $McClure^{1}$ that the smallness of the spin-orbit interaction arises from the vanishing (by symmetry) of one- and two-center spin-orbit coupling integrals that mix singlet $\pi, \pi^{*}$ and triplet $\pi, \pi^{*}$ states. This leaves only small three and four center terms to provide in-plane polarized intensity. It is found, however, that some of these one- and two-center integrals do not vanish for molecules containing atoms with d-$\pi$ orbitals. These terms are calculated for thiophene ($C_{4} H_{4}S$), and are found to make a significant contribution to spin-orbit coupling beyond that usually associated with heavy atom substitution. This contribution should introduce appreciable in-plane polarized intensity into the T $<->$ $S_{\eta}$ transition of thiophene. The implications of these ideas for the increased spin-orbit coupling in halogen (and other heavy atom) substituted aromatic molecules, and in paired spin poryphyrins is also considered. en_US dc.format.extent 108216 bytes dc.format.mimetype image/jpeg dc.language.iso English en_US dc.publisher Ohio State University en_US dc.title THE ROLE OF d-$\pi$ ORBITALS IN SPIN-ORBIT COUPLING en_US dc.type article en_US
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