Spectral diffusion of a photochemical proton transfer system in an amorphous organic host: Quinizarin in alcohol glass

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.