Photoacoustic spectroscopy method has been applied to study nonradiative processes in the excited states of Ce3+ and Cr3+ ions in YAG crystals. A comparative analysis between photoacoustic and absorption spectra has been performed.
Unexpected rise of longwave band magnitude observed in photoacoustic (PA) spectrum obtained for the YAG:Cr laser material is discussed. Explanation of this phenomenon is proposed based on comparison of measured and calculated photoacoustic signal dependence on modulation frequency. Finite lifetime of excited level has been taken into account for this reason. Contribution of PA signal generated after absorption of sample luminescence by walls of measuring cell has been considered.
The effect of nonradiative processes on spectroscopic properties of the Y3Ga5O12 crystal doped with Cr+4 has been examined. For this reason, the absorption, emission and photoacoustic spectra of the same have been measured and analyzed. For the interpretation of the obtained result the role of the nonradiative interconfigurational transfer between highly excited vibronic levels was considered. It is concluded that this relaxation mode is probably the reason for almost purely nonradiative character of the Cr+4 centers in the investigated medium.
CdS polycrystalline samples, doped by diffusion with Cu, were examined by photoacoustic spectroscopy. The relatively low dopant solubility Nd equals 2 X 1018 cm-3. This supports the suggestion that the well-known problem with the achievement of good conductivity in wide-band-gap semiconductors should be associated with the lack of good dopant solubility in the material.
Photoacoustic spectra of malachite green adsorbed on silica gel were investigated at high dye concentrations. The measurements were carried out for two markedly differing layer thicknesses of dyed silica. The ratio of maxima of two characteristic dye bands at (lambda) equals 620 nm and (lambda) equals 425 nm was chosen as an indicator of concentration dependent changes in the shapes of the photoacoustic spectra investigated. The comparison of experimental data with the theoretical model implies that the changes observed in the shape of the spectrum result first of all from the mechanism of the signal generation in inhomogeneous medium.
Infrared absorption (IR) and Fourier transformed photoacoustic spectra (FTIR PAS) of the europium dibenzoylmethane complexes are compared in the 400 - 1400 and 2400 - 3400 cm-1 regions. A close similarity has been found between the IR and FTIR PAS spectra in the whole spectral range examined, in respect of both line positions and intensity ratios. Vibration frequencies in the PAS and IR spectra and their interpretation are given.