We applied hydrostatic pressure to spectral holes burned into a resorufin doped ethanol/methanol glass. We found that the line shift is perfectly linear with pressure and showed a pronounced dependence on the burn frequency as predicted by theory [J. Chem. Phys. 90, 3274 (1989)]. We exploited the burn frequency dependence to determine the solvent shift of the dye probe and the compressibility of the alcohol glass used. On the other hand, the behavior of the hole width under pressure shows features not predicted by theory: The broadening is, like the line shift, dependent on the burn frequency within the inhomogeneous band, yet in a nonlinear fashion. We attribute the color effect in the pressure induced broadening of the hole to a breakdown of the Gaussian approximation.
Experimental data describing the time evolution of photochemical holes in organic glasses are reported. The photochemical system is 1,4-dihydroxyanthraquinone (quinizarin) in ethanol/methanol glasses; its photochemistry is based on proton or deuteron transfer processes. The experiments show a logarithmic increase of the hole widths in a time domain between minutes and about 104 min. The experimental results yield a pronounced deuteration effect and little variation with temperature between 1.35 and 4.2 K. The data are interpreted in a semiquantitative way using current theories of spectral diffusion in amorphous solids. The fastest measured photochemical rates are on the order of seconds, leaving a ‘‘time independent’’ linewidth of about 0.4 cm−1 at 1.35 K.
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