Kinetics of the cyclohexadienyl radical self-reaction and oxidation reaction using cavity ring-down spectroscopy

Visible absorption spectra of the cyclohexadienyl radical (c-C6H7) assigned to the A ∼ ← X ∼ electronic transition have been measured using laser photolysis coupled with a cavity ring-down spectroscopic detection technique. Spectral simulation of the rotational structure of an origin band at room temperature was performed using molecular constants predicted by quantum chemical calculations. Pressure dependence of the self-reaction of the cyclohexadienyl radical was measured in the pressure range of 10–100 Torr. The reaction rate coefficient of the cyclohexadienyl radical with molecular oxygen at 10 Torr N2 buffer and room temperature was determined to be (5.4 ± 0.7) × 10−14 cm3 molecule−1 s−1, which is in good agreement with previous reported value measured at 760 Torr.