HIGH-PRESSURE EFFECTS ON LOW-TEMPERATURE RELAXATION IN SOLIDS

Persistent spectral hole burning (SHB) was used to probe the influence of high hydrostatic pressure (up to 8.4 kbar) on optical relaxation in chlorin (Chl)-doped glassy (polystyrene, PS) and (poly)crystalline (n-octane, C-8 Shpol'skii system) samples at 4.2 K. Pressure induced width reduction of isobarically burnt and measured holes was found, FWHM of holes being for PS:Chl 4.3 and 2.4 GHz at 1 atm and 5.1 kbar, respectively, and for C-8:Chl (15730 cm-1 line) 130 and 45 MHz at 1 atm and 5.5 kbar, respectively. The latter value approaches the lifetime limit of 40 MHz. For the glassy matrix the effect of hole narrowing gives evidence of the dominant role of low frequency quasilocal vibrations in determining the hole width. Pressure induced instability of photoproduct was found in C-8:Chl at pressures above 5.5 kbar.