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electroactive gas, here 02. This method was carried out by using a readily available commerical controller/rotator to vary modulation frequency. The theoretical advantage of SHM that the frequency response of modulated current is independent of the concentration of the electroactive species (D remaining constant) and of the number of electrons transferred is clearly shown for this useful case.Registry No. 02,

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Three types of platinized n-type anatase titanium dioxide powders were synthesized for use as photosensitizers in the oxidation of a-methylstyrene in acetonitrile suspensions. The oxidized, reduced, and n-octyl surface derivatized powders had mean particle diameters which ranged from 6.2 to 6.8 fim and BET surface areas (N2 adsorption) which varied from 72 to 75 m2/g. Photooxidations that employed the synthesized oxidized powders had an incident monochromatic photon-to-product efficiency of 0.037 ± 0.002 using 366-nm light. This represents a 7.6-fold increase in the photoefficiency when compared with platinized commercial anatase. This increased efficiency is attributed to surface characteristics that promote interfacial charge transfer versus electron-hole recombination. The powders possess a high roughness factor (approximately 300) and a surface topography that can be described by a fractal dimension (D ~3.0). An additional 2.3-fold increase over the synthesized oxidized powders is realized for the n-octyl-derivatized powders. This additional improvement is attributed to an increase in the surface affinity of the semiconductor particles for the nonpolar hydrocarbon starting material.

the number of molecules in that level at V-V steady state vs. the number at complete V-T/R equilibrium. As the temperature increases, high-energy states will retain a larger fraction of the overall vibrationally excited-state population at V-V steady state because their Boltzmann factors are increasing most rapidly with temperature.Thus, the V-T/R amplitude should increase with increasing temperature for levels fluorescing at 5.3 pm. The observed rate for this process, corresponding to 30 collisions, is about what would be expected for a medium-sized molecule with a low-lying vibrational frequency.The decrease in 5.3-µ fluorescence intensity with the addition of argon is in marked contrast to the behavior of laser-pumped small molecules such as CH3F, S02, CH3C1, or COF2 which often show an increase in fluorescence intensity as rare gas is added. There are several possible explanations for this observation. While the most tempting is to suggest that argon collisions "kick" (COF)2 molecules which would ordinarily fluoresce at 5.3 /um into background vibrational states with no oscillator strength at this wavelength, the fact that the overall decay rate does not change significantly with argon pressure argues against this explanation. Argon does not seem to compete favorably with parent gas in causing vibrational relaxation. This suggests that much of the collisional vibrational relaxation in (COF)2 is controlled by resonant V-V energy transfer processes. Another explanation is that the argon simply broadens the spectral absorption lines causing a decease in the absorption coefficient per unit frequency range. This assumes that a majority of the excitation arises from transitions in which the laser frequency is near the center of a vibration-rotation line. Although this as-