HYPERQUENCHED GLASSY FILMS OF WATER - A STUDY BY HOLE-BURNING

The results of infrared absorption (-OH) experiments and nonphotochemical hale-burning experiments of aluminum-phthalocyanine-tetrasulfonate (ATP) in hyperquenched glassy films of water (HGW) are reported. Films were produced by deposition of Liquid water clusters (similar to 2 mu m), generated by a thermal spray nozzle source, onto either a sapphire or polycrystalline copper cryoplate. Deposition temperatures (T-D) in the similar to 5-150 K range were employed. T-D = 5 K films were annealed at various temperatures (T-A) up to 140 K. For each value of T-A, the infrared and hole-burning properties (zero-phonon hole width and hole growth kinetics) of the film (annealed) are identical to those of unannealed HGW formed at T-D = T-A. Thus, HGW formed at a deposition temperature of T-D' is kinetically accessible, by annealing of HGW formed at temperatures T-D < T-D'. Dramatic irreversible manifestations of configurational relaxation in HGW are observed to onset at T-A (T-D) similar to 90 K. This configurational relaxation progresses smoothly with temperature up to 150 K (highest T-D and T-A used). Zero-phonon hole widths were usually determined for a burning and reading temperature of 5 K. Hole growth kinetics were always monitored at a burning temperature of 5 K. It was found, for example, that HGW annealed or deposited at 140 K yields a zero-phonon hole width of 180 MHz, a factor of 3 times narrower than the hole of HGW formed at T-D = 5 K. Decrease of the hole width with annealing onsets at T-A similar to 90 K. Both unannealed and annealed films yielded a T-1.3 power law for the dependence of the hole width on the burning temperature (less than or similar to 10 K), proving that pure dephasing/spectral diffusion is governed by the electron-TLS(int) (intrinsic two-level systems) interaction. An interpretation of the aforementioned configuration relaxation, onsetting at similar to 90 K, in terms of the TLS(int), model is given. ATP in HGW turns out to be the most efficient system for nonphotochemical hole burning yet discovered, with an average quantum yield as high as 0.18. (The S-1 lifetime of ATP is 4.8 ns.) Remarkably, the hole burning is essentially inoperative in cubic ice formed by warming of HGW. However, this cessation is consistent with the current mechanism for nonphotochemical hole burning.