A CONSISTENT DESCRIPTION OF EPR-SPECTRA

An explicit expression for the EPR absorption signal is presented as a two-variable function, S(B, ω), based on general theoretical and experimental grounds. Formulation of the lineshape function and the Boltzmann factor in S(B, ω) are reexamined by refining the description of the spin Hamiltonian of a system, which reveals a conceptual distinction between the resonance condition and the equation for calculating the resonance center. Expressions for the comparison of EPR spectra detected by field modulation and frequency modulation are derived for both single-crystal and powder systems, which indicates that the two modulation schemes are in general not equivalent. Some nonrigorous treatments of the 1/g factor introduced by R. Aasa and T. Vanngard (J. Magn. Reson. 19, 308, 1975) are corrected. A number of inconsistencies in many classic magnetic resonance publications are indicated. © 1991.