Garnets infrared spectra

Newman, D. J., Price, D. C. Runciman, W. A. (1978) Superposition model analysis of the near-infrared spectrum of Fe2+ in pyrope-almandine garnets. Amer. Mineral., 63, 1278-81. 

Neodymium and YAG Lasers. The principle of neodymium and YAG lasers is very similar to that of the ruby laser. Neodymium ions (Nd +) are used in place of Cr + and are often distributed in glass rather than in alumina. The light from the neodymium laser has a wavelength of 1060 nm (1.06 xm) it emits in the infrared region of the electromagnetic spectrum. Yttrium (Y) ions in alumina (A) compose a form of the naturally occurring garnet (G), hence the name, YAG laser. Like the ruby laser, the Nd and YAG lasers operate from three- and four-level excited-state processes. 

The technique of laser heating in a DAC is based on three main features optical transparency of diamond anvils the samples can be heated via the optical absorption of intense laser radiation, and the temperature can be determined from the thermal radiation spectrum of the heated sample using the Planck formula [10]. Laser radiation for heating of a sample in a DAC was first implemented by Ming and Bassett [11], who used a pulsed ruby laser, and a continuous-wave Nd-YAG (yttrium-aluminum-garnet) laser to heat samples in a DAC above 3300 K, and up to 2300 K, respectively. Today two types of continuous wave infrared (IR) lasers are extensively used in laser heating experiments Solid state lasers (Nd-doped YAG, or YLF (yttrium-lithium-fluorite) crystals with the most intense line at... 

The theory of the effect of crystal structure on k is still in a very rudimentary state. It is generally observed that the larger the number of optical branches in the phonon spectrum, the lower the thermal conductivity. In garnets, there are 80 atoms in the primitive unit cells, and there are 97 optical modes at the zone center (Hurrell et al., 1%8). The combination of infrared and Raman studies has... 

White, R. G., 1964. Handbook of Industrial Infrared Analysis. New York Plenum Press. Wickersheim, K. A., R. A. Lefever, and B. M. Hanking, 1960. Infrared absorption spectrum of the silicate ion in the garnet structure. J. Chem. Phys. 32 271. 

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