Experiments directed toward elucidating the nature of fragments produced by the photodissociation of ClN3 have been performed. The utlraviolet absorption spectrum of this molecule exhibits three features between 300 and 170 nm, with λmax = 250, 205, and <170 nm. The shortest wavelength feature (whose maximum was not resolved) was the strongest of the three, with ε170 = 5000 ℓ mol−1 cm−1. Photolysis of ClN3 at 193 nm produces N2 and NCl fragments in both the singlet and triplet manifolds. In the singlet manifold of fragments, emission from electronically excited NCl(b 1Σ+) was observed. The NCl(b 1Σ+) molecules are also vibrationally excited, and emission from levels as high as v′ = 10 was recorded. Time resolution of the NCl(b 1Σ+) emission indicated that the higher vibrational levels were quenched by the gas mixture (∼3% ClN3 in helium) much more rapidly than the lower vibrational levels. The rate constant for quenching of the low v′ levels (v′ = 0–2) of NCl(b 1Σ+) was determined to be kQ = (1.72±0.05)×103 s−1 Torr−1; the rate constant for quenching of the higher levels (v′?8) was found to be kQ = (3.8±0.2)×104 s−1 Torr−1. The spontaneous emission rate for NCl(b 1Σ+), v′ = 0–2, was measured to be A = 1590±160 s−1. In the triplet manifold of fragments, photolysis at 193 nm produces excited N2(A 3Σ+u) metastable molecules. The presence of this species was determined from the observation of N2(C 3Πu)→(B 3Πg) emission produced by energy pooling processes, and from the excitation of NO by energy transfer from the N2 metastables. Photolysis of ClN3 produces at 193 nm excited singlet and triplet fragments with comparable probability. Photolysis at 249 nm also generates both excited singlet and triplet NCl and N2 fragments. Emission from vibrationally excited NCl(b 1Σ+) was again observed, and the initial vibrational distribution appeared to be similar to that found for photolysis at 193 nm. The yields for production of NCl(b 1Σ+) at 193 and 249 nm are approximately equal. Photolysis at 249 nm also produces N2(A 3Σ+u) fragments, although in substantially smaller yield than found at 193 nm.

Chemiluminescence from the a l A and 6'8' excited electronic states of nitrogen halide diatomics is observed when HN, is allowed to react with mixtures of halogen atoms in a discharge-flow apparatus. Excited NF (a'A) is produced by the F + HN, reaction, and NC1 (a'A, b'8') and NBr (dA, 6'8') are produced by the F, C1, + HN, and F, Br + HN, reactions, respectively. In the low-density limit, the yield of NF(a'A) was found to be near unity. The yields of the b'8+ states of NCl and NBr were determined to have a lower limit of ca. 10%. A number of results from these experiments, including direct observation of N, radicals in the flow, support a hypothetical mechanism in which N, acts as an intermediate. A second possible mechanism proceeding via an HNF intermediate cannot be ruled out.

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The production of both the blB+ and alA states of NCI has been observed from the reaction of HN3 with flowing streams of C1 and F atoms. The results suggest that a two-step reaction sequence is responsible for the production of excited NCI, as follows:The rate contant (all products) for the first step is k(F + HN3) > 1 X cm3/molecule sec.Comparison of this value to results obtained in a previous study of the F + HN3 system yields a value k(F + N3) = 2 X 10-l2 cm3/molecule sec. The rate constant for the reaction of chlorine atoms with HN3 was determined to be k(C1+ HN3) < 1 X 10-l2 cm3/molecule sec. The difference between the C1 + HN3 and F + HN3 rates is interpreted in terms of an additionelimination mechanism.