Spin correlation function of benzene and naphthalene from spin-coupled wave functions

In this paper we report on the calculation of the spin correlation function describing the dipolar spin-spin interaction for benzene and naphthalene i n their lowest excited triplet state. Spin-coupled wave functions were used . The spin correlation function measures the contributions to the [3S(z)(2) -S-2] expectation value arising from electrons located at different points. An alternation of positive and negative correlation dependent on the separ ation of the unpaired electrons is found. The results are used to analyze a nd interpret the zero-field splitting parameter D of these molecules in ter ms of different contributions. The relationship between the spin correlatio n function and the sequence of the zero-field levels as well as the value o f the parameter D and its dependence from molecular size is discussed. (C) 2001 American Institute of Physics.