The Cu*(2D5/2 and 2D3/2) chemiluminescent reactions with ClF

Abstract

The chemiluminescence from CuCl* and CuF* molecules formed by the reaction of metastable ²D_3/2 and ²D_5/2 copper atoms with ClF was studied at room temperature. The Cu* atoms were generated in a hollow-cathode, flowing-afterglow reactor. A strong preference (∼15∶1) for production of electronically excited CuCl* over excited CuF* was found. Computer simulations of the observed spectra provided electronic branching ratios, as well as vibrational distributions within each CuCl* and CuF* electronic state. The vibrational energy disposal for CuCl*, 〈f_v〉 = 0.06–0.32, was similar to, or smaller than, the statistical value, whereas 〈f_v〉 was much larger (≈0.6) for the CuF* products. The total rate constants for the reaction of ground ²S and metastable ²D_5/2 and ²D_3/2 states of Cu atoms with ClF were measured as 28 ± 3, 8.8 ± 2.5 and 10 ± 3 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The highest observed CuF*(b ³Π_0⁺,1) vibrational levels from the ClF and F₂ reactions were used to recommend D₀(CuF) = 34 300 cm⁻¹. The results from ClF were compared with the data from the analogous F₂, Cl₂ and Br₂ reactions. The branching fractions for chemiluminescent products decline in the order F₂ > Cl₂ > ClF > Br₂, and the formation of CuX(X) from reactions of the Cu*(²D_5/2 and ²D_3/2) atoms becomes more important in the series. The reactions of the ground and metastable-state copper atoms with SOCl₂, CCl₄ and PCl₃ also are discussed.