Decay of ESR nutation signals fromE′1 centers in quartz

Decay of time-dependent nutation signals from E′₁ centers in crystalline quartz is investigated at room temperature. ESR-nutation signals were excited in the single-photon mode and were shaped by Zeeman field pulses. It is found that the decay of this signal follows an exponential law with a rate Λ substantially smaller than 1/T₂ (T₂ being the transverse relaxation time) and increases with the amplitude of the acting ultrahigh-frequency field B₁. It is shown with the use of the Bloch equations that the intergral decay rate of nutations in an inhomogeneously broadened two-level system depends on the ratio of B₁ to the linewidth and increases nonlinearly with increasing B₁. The observed quantitative disagreement between the experimentally observed nutation decay with Bloch's theory is explained by the stochasticity of conditions of the resonant interaction of radiation with a system of spins. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 213–219, March–April, 1999.