John M. Bowen

Growth, characterization, and optical spectroscopy of Al2O3:Ti3+

The process of growing large diameter single crystals of Al2O3:Ti3+ by vertical solidification of the melt is described, and some of the problems in producing high‐optical quality material are discussed. The characterization of the distribution and valance state of titanium ions was performed by x‐ray techniques and laser Raman microprobe methods. The presence of other impurity ions, specifically iron, was also determined. In some cases titanium was found in the grown crystal to be in the rutile form. In addition, Ti‐Fe pairs, and concentrated regions of titanium on the surface of the boule were also observed. Some procedures for minimizing these problems are discussed. The results of optical absorption, fluorescence, and lifetime measurements are reported. The addition of Fe is shown to produce a broad absorption band in the red region of the spectrum, and two‐photon laser excitation terminating in the ultraviolet spectral region produces a broad blue emission band.

Spectroscopic properties of alexandrite crystals II

Abstract Several aspects of the optical spectroscopic properties of alexandrite crystals not previously investigated are reported here. For Cr3+ ions occupying the Al3+ lattice sites with mirror symmetry in BeAl2O4, the positions of the zero-phonon lines for absorption transitions to the 2T1g and 4T2g levels are identified, and vibronic transition peaks in the fluorescence spectrum are compared to transitions appearing in the Raman spectrum and Stokes excitation spectrum. In addition, the effects of radiation trapping are shown to lengthen the fluorescence lifetime of the 2Eg - 4A2g transition for ions in these sites at low temperatures. For Cr3+ ions occupying the Al3+ lattice with inversion symmetry, the ground state splitting of the 2Eg - 4A2g transition is reported and the decrease of the fluorescence lifetime with temperature is shown to be due to the increase in vibronic emission probability as well as increased probability of direct radiationless decay.

Quantitative determination by circular dichroism of lysergic acid diethylamide in confiscated material

D-Lysergic acid diethylamide has been quantitated in a variety of confiscated specimens by circular dichroism spectropolarimetry. Separation of the drug from the specimens was unnecessary. The minimum quantity detected was approximately 2 μg.

Circular Dichroism: An Alternative Method for Drug Analysis

A case is made for the acceptance of circular dichroism spectropolarimetry as a method for the direct and quantitative analysis of controlled substances in solid dosage forms of drugs. The method is critically described and results are included for the analysis of codeine, heroin, L-cocaine, and D-lysergic acid diethylamide.