The N C O + N O reaction was studied by time-resolved infrared diode laser spectroscopy. The C02 + N2 channel was found to account for 56 f 7% of the total reaction rate, with N 2 0 + C O accounting for the remaining 44 f 7%. These branching ratios were found to be independent of temperature in the range 296-623 K. Furthermore, the C N + 0 2 reaction at room temperature produces C O + N O products with a yield of 23 f 10% in addition to the N C O + 0 channel, with a significant negative temperature dependence. Product energy disposal studies were also performed. C O vibration and the v3 mode of CO2 were found to account for only 0.55% and 3.4% of the available energy, respectively. These results are discussed in terms of statistical models and simple a b initio computations.

The reaction NCO + NO -products was studied at room temperature using pulsed laser photolysis with time-resolved infrared diode laser detection. C02, CO, and N20 reaction products were detected by infrared absorption under quantum-state relaxed conditions to provide absolute number densities of each species. The results indicate that three product channels are active: C02 + N2 is the most important channel, with CO + N2 + 0 and N 2 0 + CO also contributing significantly.

The structure of a new heteroaromatic sulphur compound has been determined; the results support the inclusion of d-orbitals in CNDO molecular orbital calculations.ALTHOUGH derivatives of 2,2'-bi-l, 3-dithiole have been examined, it is only recently that Wudl et aZ.1 have isolated the parent compound itself which being an odd-membered sulphur-containing heterocycle, is expected to be a planar aromatic system, similar to the sulphur-containing systems examined by Visser et aZ.2 We have determined the crystal structure of 2,2'-bi-1,3-dithiole and compared the results with predictions based on CNDO calculations.2,2'-Bi-1,3-dithiole forms orange, light-sensitive needles; crystal data: C,H4S,, monoclinic, a = 7.364, b = 4.023, G = 13.922 A, = 101.42*, 2 = 2, space-group P2,/c, p = 10.77 cm-l. 2496 independent hkl intensities were collected on an automated Picker full-circle diffractometer with Mo-K, (A = 0.71069 A) radiation. The structure was solved by the standard heavy-atom method, and the model, including the hydrogen atoms, was refined by full-matrix least-squares to a final R of 0.048 on the observed data.

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A beryllium-walled cryostat is described which allows collection of nearly a full sphere of accurate three-dimensional X-ray diffractometer data at liquid-nitrogen (LN2) and liquid-helium (LHe) temperatures. Cryogen consumption is 0.3-0.4 liters of LHe per hour at 30~K and 0.1-0.2 liters of LN2 per hour at 78 °K. The specimen is mounted on a copper block, the temperature of which is controlled to within 0.1 °. Measurements with a powder sample of TbVO4 show that at 33~JK the specimen temperature is within 2 ° of the temperature of the copper block. The cryostat has been used for the collection of several low-temperature data sets. Some special modifications in data-collection and dataprocessing software are described.