Although TiO 2 is generally considered to be an oxygen deficient n-type compound, the role of oxygen vacancies and Ti 3+ ions on its photocatalytic activity is not fully understood. In this study, we investigated the effects of high-temperature calcination and H 2 reduction treatment on the water oxidation activity of rutile TiO 2 under ultraviolet irradiation. Calcination above 900 °C decreased the photocatalytic activity of the TiO 2 owing to strong oxidation, but its initial activity was restored by H 2 treatment at above 500 °C. Electron spin resonance (ESR) spectra showed that the hightemperature calcination created O •− radicals (trapped hole in oxygen lattice site), while the H 2 reduction treatment created Ti 3+ ions (trapped electron in titanium lattice site) with oxygen vacancies. Diffuse reflectance ultraviolet−visible−near-infrared (UV− vis−NIR) spectroscopy indicated an increase in the amount of electrons in shallow traps and the conduction band with H 2 treatment temperature. Measurements of the sheet resistance and space charge layer capacitance of the thermally oxidized TiO 2 films indicated that the H 2 treatment improved the electrical conductivity owing to an increase in donor density (electron density). Thus, the increase in the photocatalytic and photoelectrochemical activities of the rutile TiO 2 was attributed to donor doping by H 2 reduction.

Raman and infrared spectra in the region of 1800-150 cm-l were recorded for a set of cis-trans isomers of B-carotene, i.e. the all-trans, 7-cis, 9-cis, 1 3 4 and 154s isomers. Spectral comparison revealed Raman and infrared key bands which (1) distinguish stretched or terminal-bent configurations (all-trans, 7-cis and 9 4 ) from central-bent configurations (13-cis and 15-cis), and (2) distinguish unmethylated 7-cis and 1 5 4 s Configurations.Keybands (1) include Raman bands at 1160 and 1140 cm-' and infrared bands a t 825 and 775 cm-' (the intensity varies with the position of the cis-bend). Key bands (2) include Raman bands a t 1274 and 962 cm-' and an infrared band at 741 cm-' (characteristic of the 7-cis configuration), and also a Raman band a t 1247 cm-' and an infrared band at 775 cm-' (characteristic of the 1 5 4 s configuration). The normal modes for the key bands were determined by a set of normal coordinate calculations for the isomeric configurations of a simplified model of Bcarotene. The key bands were mainly related to the C-H in-plane bendings, coupled with the C=C or C-C stretching, or to the C-H out-of-plane wagging vibrations, some of which coupled with the C=C torsion.

UV-induced photoisomerization of acetylacetone in low-temperature argon matrixes has been studied by Fourier transform infrared spectroscopy. Identifications of the species produced by UV irradiation (λ > 280 nm) were carried out with the aid of the density functional theory (DFT) calculation, in which the 6-31G* basis set was used to optimize the geometrical structures. By comparison of the observed infrared bands with the calculated spectral patterns, it was found that cis−trans isomerization around the C−C, CC, and C−O bonds occurs to produce less-stable enol isomers, 2-hydroxy-2-penten-4-one. Shorter-wavelength irradiation (λ < 280 nm) induced hydrogen-atom migration of the enol isomers to produce a keto isomer, 2,4-pentanedione.

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