Electron-spin double resonance by longitudinal detection. II. Signal dependence on relaxation times

The line shape of the longitudinally detected electron-spin-resonance (LODESR) signal is studied as a function of the relaxation times of the considered spin system. Assuming low saturation as an approximation, analytical expressions of intensity and linewidth are obtained for the signals due to some main harmonics. These results are compared with experiments performed on different spin systems in solids. Direct measurements of microwave field strength in the resonant cavity have been obtained by a new technique using the field-induced shift of the resonance frequency of a spin sample. Comparison of LODESR method with some other doubleresonance effects is discussed. Finally, it is shown with experiments that the LODESR method provides in a simple way an immediate measure of variations of longitudinal relaxation times. © 1977 The American Physical Society.