Infrared Chemiluminescence in the System H+NOCl

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Abstract
Infrared emission has been observed arising from the low-pressure gas-phase system H+NOCl; HCl emission consists of the fundamental spectrum (Δv=1), and first and second overtones (Δv=2 and 3) of the ground electronic state. HCl† (vibrationally excited HCl in its ground electronic state) must be present in levels up to and including v=9 (possibly 10). The distribution of HCl† among vibrational levels is non-Boltzmann, indicating that some or all are formed by a chemical reaction rather than a thermal process. This reaction is thought to be H+NOCl→HCl†+NO. Only a weak emission due to NO† was observed. An emission of intensity comparable to HCl† was observed in the region of the ω1 fundamental of NOCl. From the stationary state distribution of HCl† among vibrational levels a calculation was made of the relative rate constants kv for reaction into each accessible vibrational level of HCl†. An examination of the stationary state distribution of HCl†v=1 among rotational levels indicates that while the over-all distribution is non-Boltzmann, rotators in high rotational levels are in approximate equilibrium at ∼2000°K and rotators in the lowest levels are in a distribution which roughly corresponds to that for 650°K. The absolute intensity of the infrared emission was found to be ∼0.05 w. This is equivalent to roughly 0.2 to 2.0% of the energy liberated by the reaction. From the emission intensity the partial pressure of HCl†v=1 was calculated to be ∼6×10—3 mm Hg, that is ∼0.3% of the total reagent pressure.

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