GaN p–i–n photovoltaic diode arrays were fabricated from epitaxial films deposited on sapphire by molecular beam epitaxy. Peak UV responsivity was 0.11 A/W at 360 nm, corresponding to 48% internal quantum efficiency. Visible rejection over 400–800 nm was 3–4 orders of magnitude. Typical pulsed time response was measured at 8.2 μs. Spectral response modeling was performed to analyze the photocurrent contributions from photogenerated carrier drift in the depletion region and from minority carrier diffusion in the p and n layers. With the model, a maximum internal quantum efficiency of 55% at 360 nm was calculated for the photovoltaic diode structure.

The spectra of vibrationally hot HOI formed in the reaction of alkyl iodides with oxygen atoms are observed by Fourier transform infrared emission spectroscopy. The v=1–3 levels of the OH stretch are observed via the Δv=−1 and Δv=−2 sequence bands. The spectrum of DOI is observed by using 2,2,2-d3-iodoethane as the precursor in the oxygen atom reaction. The v=1–4 levels of the OD stretch are observed in the Δv=−1 sequence band, and the v=1–5 levels of the OD stretch are observed in Δv=−2. Medium resolution spectra (0.031 cm−1 apodized) are recorded and rotationally analyzed for the ν1 fundamental and 2ν1−ν1 hot band of HOI. An estimate of the HOI ground state structure is made by constraining the OH bond length to its value for HOCl and HOBr and calculating the HOI bond angle and the OI bond length by least squares fit to the ground state rotational constants.

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The emission spectra of vibrationally excited hydroxyl radical products formed in the reactions of alkyl radicals with O(3P) atoms are detected using a laser photolysis/time-resolved Fourier transform infrared spectroscopy technique. For the reaction between oxygen atoms and ethyl, the radicals are produced simultaneously by the 193 nm photolysis of the precursors SO2 and diethyl ketone, respectively. The observed initial OH(v) product vibrational state distribution for the C2H5+O(3P) reaction is 0.18±0.03, 0.23±0.04, 0.29±0.05, 0.23±0.07, and 0.07±0.04 for v=1 to 5, respectively. The population inversion is best explained by a direct abstraction mechanism for this radical–radical reaction. Vibrationally excited hydroxyl radicals are also observed in the O+ethyl, O+n-propyl, and O+i-propyl reactions when using alkyl iodides as precursors of the alkyl radicals, although quantitative detail is not obtained due to competing reaction processes.