Magnetic Resonance and Rapid Passage in Irradiated LiF

The experimental result of Portis that at room temperature the paramagnetic dispersion signal ($\frac{d{{\chi }_m}^{\prime }}{\mathrm{dH}}$) of radiation-induced paramagnetic centers in LiF has the shape of an undifferentiated Gaussian curve and lags the modulation field by 90 degrees has been confirmed. His theory, explaining this result as a manifestation of rapid-passage behavior, has been tested over a range of experimental parameters and appears valid. In terms of this theory we found that the spin-lattice relaxation time $T_1=1.5\mathrm{}\times {10}^{-4\mathrm{}}$ sec at room temperature.