Abstract :
The spin–lattice relaxation time was determined by electron spin echo (ESE) method in the temperature range 30–300 K. Various possible contributions to the relaxation rate are discussed. The relaxation rate increases about three order of magnitudes in this temperature range and is described by equation 1/T1=bT2+c cosech2(Δ/2kT). The first term is related to the damage of the crystals produced by γ-rays, whereas the second one describes local mode contributions with energy Δ=403 cm−1 (288 cm−1 in deuterated crystal). Deuteration results in a decrease in the value of the b and Δ parameters and produces significant change in the angular dependence of the relaxation rate. The universal behavior of the relaxation in irradiated crystals is pointed out.
