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VUV kinetic spectroscopy of ClO₂ and vibrational energy distributions in O₂ produced from NO₂ and ClO₂ by flash photolysis Morse, Robert Donald

Abstract

A flash photolysis apparatus suitable for kinetic spectroscopy in the vacuum ultraviolet is described. Four new Rydberg transitions of ClO₂ have been observed and their measurements given. Molar extinction coefficients of the previously reported bands of ClO₂ have been measured. Two of these electronic transitions (and possibly a third) have been assigned to a Rydberg series converging to the first ionization potential (10.36 eV). The flash photolysis of ClO₂ followed by kinetic spectroscopy in the vacuum ultraviolet has yielded a new spectrum of ClO. Six electronic transitions have been assigned; all are Rydberg in nature. The first four of these transitions are thought to be ²Σ ← X²π[sub i] from which a spin orbit coupling constant, A=-318 ± 5 cm⁻¹ is obtained for the ground state. Hot bands in three of the above systems of ClO have been observed in absorption. This has enabled the direct measurement of the ground state vibrational constant (ω[sub e]= 859 ± 6 cm⁻¹) for the first time. Extinction coefficients for a number of the ClO transitions have been measured. A kinetic study of ClO recombination by kinetic spectroscopy of these very strong and well resolved vibrational bands of ClO and ClO₂ has been initiated. This preliminary study showed that ClO decay is second order over its first two half lives, in agreement with previous results; at longer times, however, a deviation was noted. Initial vibrational energy distributions in O₂ produced from the flash photolysis of NO₂ and ClO₂ have been measured. Absolute populations of the levels ν"= 1 to 7 have been combined with previously measured relative populations of the levels 6 to 13 for the O₂ distribution from ClO₂ to give a complete initial vibrational energy distribution. Populations of the levels ν"= 4 to 13 of O₂ from NO₂ have been measured. Both distributions show that the initial energy content in O₂ is a significant portion of the heat of reaction. Extensions of the NO₂ distribution to include all of the levels observed, but not measured due to experimental difficulties, are discussed.

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