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

The results of infrared absorption (-OH) experiments and nonphotochemi cal hale-burning experiments of aluminum-phthalocyanine-tetrasulfonate (ATP) in hyperquenched glassy films of water (HGW) are reported. Film s were produced by deposition of Liquid water clusters (similar to 2 m u m), generated by a thermal spray nozzle source, onto either a sapphi re or polycrystalline copper cryoplate. Deposition temperatures (T-D) in the similar to 5-150 K range were employed. T-D = 5 K films were an nealed 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 an d 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 depositio n temperature of T-D' is kinetically accessible, by annealing of HGW f ormed 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 smoothl y 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 tempera ture of 5 K. Hole growth kinetics were always monitored at a burning t emperature of 5 K. It was found, for example, that HGW annealed or dep osited at 140 K yields a zero-phonon hole width of 180 MHz, a factor o f 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 u nannealed and annealed films yielded a T-1.3 power law for the depende nce 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, onsett ing 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 burnin g is essentially inoperative in cubic ice formed by warming of HGW. Ho wever, this cessation is consistent with the current mechanism for non photochemical hole burning.