Relaxation in ruby

The relaxation of the (1\u21942) and (2\u21943) transitions in chrome-doped Al2O3 (0.015%) has been studied at S-band, using a pulsed microwave method, over a range of crystal orientations in the magnetic field at temperatures of 77 deg;K to 50 deg;K, and at 4.2 deg;K and 1.6 deg;K. A T 127 variation of the relaxation time with temperature was found in the liquid nitrogen range. The relaxation time in this temperature range was found to be independent of crystal orientation, and for the (1\u21942) transition was 50 microseconds at 77 deg;K. At liquid helium temperatures, harmonic cross relaxation was present over most of the range of the crystal orientation studied and was observed at harmonic-to-signal frequency ratios of 2:1, 3:2, and 1:2. The harmonic cross relaxation times were typically 10 to 100 times shorter than the lattice relaxation times, and were independent of temperature. At non-harmonic points at 4.2 deg;K, the spin\u2013lattice relaxation could be described by one time constant, a value of 300 milliseconds being typical. At harmonic points anomalously long relaxation times as high as 12 seconds were observed.The authors were affiliated with the National Research Council of Canada, Radio and Electrical Engineering Division when they authored this article.Les auteurs \ue9taient affili\ue9 avec le Conseil national de recherches du Canada, Division de la radio et du g\ue9nie \ue9lectrique lorsqu\u2019ils ont r\ue9dig\ue9 cet article.Peer reviewed: YesNRC publication: Ye