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Vibrationally excited oxygen with up to 15 quanta of energy has been produced in the flash photolysis of NO₂ . When the NO₂ was selectively photolysed such that only radiation below 4000 A° was admitted to the reaction vessel the highest level observed was reduced to v" = 11 which in terms of vibrational energy corresponds to the exothermicity of the reaction O + NO₂ —> NO + O₂ Relative population ratios for the successive vibrational levels v" = 6 to 11 were calculated for both the filtered and unfiltered photolysis of NO₂ using two independently calculated arrays of Franck-Condon Factors. In both cases the ratios showed that the population distribution was definitely non Boltzmann. in that the levels were almost equally populated. The distribution for the unfiltered experiments gave a pronounced dip at v" =11 indicating that the levels 12 ≤ v" ≤ 15 are formed by a second reaction. This reaction has been shown to be Q+ NO*₂—> O*₂ v" ≥12 +NO where the NO₂ is probably electronically excited. The adiabatic flash photolysis of both NO₂ and SO₂ has been investigated. These spectra show weakening of their banded structure up to 100 microseconds after the flash and then gradual strengthening until back to normal by 10 milliseconds. This effect is well known for SO₂ and has been postulated to be the result of the formation of a high temperature isomer of SO₂. Subsequently the postulated isomer had a transient spectrum in the vacuum ultraviolet assigned to it. We have found that the weakening of both the NO₂ and SO₂ banded structure is the result of temperature broadening. The spectrum assigned to the SO₂ isomer has been extended. It has also been produced from the flash photolysis of SO₂ under isothermal conditions showing that its assignment to a high temperature isomer is incorrect. From kinetic data this spectrum in the 1800 A° region and another the 1400 A° region has been tentatively identified as two triplet systems of SO.

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.