Infrared chemiluminescence in the reactions of 0.45 eV hydrogen atoms with Cl2, SCl2 and PCl3

Abstract

Infrared chemiluminescence from HCl has been observed in “arrested relaxation” experiments to yield vibrational and rotational distributions from the reactions H+Cl2, SCl2 and PCl3, where H denotes hydrogen atoms with translational energy of 0.45 eV. The following relative populations were determined: Nv-1: Nv-2: Nv-3: Nv-4: Nv-5: Nv-6 = 0.89:1.00:0.84:0.47:0.26:0.11 for H+Cl2: Nv-1: Nv-2: Nv-3: Nv-4: Nv-5: Nv-6 = 0.80:1.00:0.72:0.48:0.24:0.10 for H+SCl2: Nv-1: Nv-2: Nv-3: Nv-4: Nv-5 = 0.79:1.00:0.88:0.36:0.14 for H+PCl3. In all three reaction systems the chemiluminescence was attributed to the primary chlorine abstraction. Comparison with the results of the thermal processes (0.04 eV hydrogen atoms) led to the following conclusions: for H+Cl2 the excess of translational energy is transformed into translational product energy and rotational energy of the molecule HCl; for H+SCl2 the excess of translational energy is transformed mainly into translational energy of the products and perhaps internal energy of SCl; for H+PCl3 the excess of translational energy allows the observation of the primary abstraction reaction, which could in earlier experiments at 300 K not be separated from secondary chemiluminescent processes. Bimodal rotational distributions were confirmed for several vibrational states of HCl formed in the systems H+Cl2, and H+SCl2. Bimodal rotational distributions were also detected in the chemiluminescent reaction H(0.04 eV)+CH3SCl → HCl(v ⩽ 5)+CH3S.