Microwave spectroscopy of some maser materials

Abstract

Vapour phase rubies were examined by several techniques. X-rays showed that the c-axis varied from place to place in each boule by up to 3º. Superimposed on this was a distribution of mosaic structure with the c-axis varying from grain to grain by up to 3º. Annealing did not improve these imperfections. Boules grown in the 90º orientation showed less mosaic than those grown in other orientations. Polygonisation, observed by Scheuplein and Gibbs (1960), provided an explanation. X-ray examination of corundum gave similar results. The random dislocation density revealed by etching was about l0(^5) dislocations/cm(^2) in corundum and ruby, therefore, adding chromium did not produce dislocations. The imperfections did not correlate with the boules, crystallography. The paramagnetic resonance linewidth increases with the imperfection in the sample and this increase is angular dependent. The basic linewidth depends on the chromium concentration. Sample 337c showed little angular broadening in the + (^1)(-2) to + (^3_)(_2) and the – (^3)(_2) to – (^1)(^2) transitions. In G2a the latter transition showed a maximum broadening of about 2(^1)(_2) times near the polar angle 45º. X-rays showed that each sample had similar c-axis misorientations but G2a contained much more mosaic than 337c. The misorientation predicted by the broadening G2a is 0º 25. The – (^1)(_2) to + (^3)(_2) transition in 337c was about 22 oersteds wide and did not vary much with angle. In G2a this transition broadened to 33 oersteds at polar angles 45º and 30º. The chromium concentration predicted from the basic linewidth at 55º in both sample is 0.43 weight % of chromium. The concentrations given by chemical analysis are 0.052 weight % for 337c and between 0.02 and 0.032 weight % for G2a.