E.P.R. lineshapes in maser materials

Using a 35 Gc/sec spectrometer, E.P.R. linewidths have been measured in a number of synthetic ruby specimens grown by various means. In addition, measurements of both linewidth and relaxation time have been made on a number of specimens of calcium tungstate doped with neodymiura. Using a mathematical treatment of the second moment, the homogeneously broadened ruby line has been resolved into concentration-dependent and concentration-independent components. The observed constant nature of the former suggests that the effective concentration of paramagnetic centres is not indicative of the true chemical concentration. Analysis of the inhomogeneous ruby line results in broadening components representative of axial misorientation and strain, A moderate correlation is obtained between misorientation figures derived from x-ray and e.p.r. measurements, and a similar correlation exists between strain and spin-lattice relaxation times. There appear to be no significant differences between the various types of flame-fusion material available. Preliminary analysis suggests that the homogeneous line in calcium tungstate owes its width to processes similar to those occuring in ruby, but strain does not appear to be predominant in the inhomogeneous broadening. Relaxation times in this material exhibit concentration and orientation dependence and a temperature dependence has been fitted empirically in the Direct and Raman regions.