A NEW APPROACH TO CALCULATING ESR-SPECTRA WITH REGARD FOR THE SATURATION AND MODULATION EFFECTS

The problem of calculating spectra determined by three methods of ESR signal recording under steady-state conditions in the presence of satu rating microwave fields and with modulation: (i) ESR with Zeeman modul ation, (ii) ESR with power modulation, (iii) electron double resonance , is formulated in a general mathematical form. A rigorous theoretical approach (stochastic Liouville equation) is used to accurately descri be interaction of a radical with external magnetic fields and with its surrounding in a condensed phase. Stochastic rotations of radicals ar e described by means of a diffusion operator written in the general fo rm. The resulting equation is reduced to a set of linear algebraic equ ations which allow the use of fast algorithms for their numerical solu tion (because the sweep variable is written as a multiplier of a unit matrix). Feasibility of the use of the Lanczos algorithm applicable to an asymmetric matrix and the Pade approximation method is discussed.