Simulation of slow-motion CW EPR spectrum using stochastic Liouville equation for an electron spin coupled to two nuclei with arbitrary spins: matrix elements of the Liouville superoperator

An algorithm is developed that extends the well known nitroxide slow-motional continuous wave electron paramagnetic resonance (EPR) simulation technique developed originally by Meirovitch et al. E. Meirovitch, D. Inger, E. Inger, G. Moro, J.H. Freed, J. Chem. Phys. 77 (1982) 3915-3938], and implemented by Schneider and Freed D.J. Schneider, J.H. Freed, Calculating slow motional magnetic resonance spectra: a user's guide, in: Biological Magnetic Resonance, vol. 6, Plenum Publishing Corporation, 1989]. This paper deals with the more general case of coupling of one electron spin to two nuclear spins. A complete listing of the matrix elements of the Liouville superoperator for this extension has been included. This advance has been successfully tested by reproducing the observed spectral lineshapes of a solution of the novel radical Mes(*)(CH(3))P-PMes(*) Mes(*)=2,4,6 (tBu)(3)C(2)H(2)] in tetrahydrofuran (THF), in which the radical is undergoing slow tumbling, with the coupling of one electron spin to two physically and magnetically inequivalent phosphorus ((31)P) nuclei.