Reaction kinetics of nitrate radicals with terpenes in solution studied by cavity ring-down spectroscopy

The use of cavity ring-down spectroscopy for kinetic measurements of photo-induced reactions in solution has been demonstrated for the first time. Second-order rate coefficients for reaction of NO3 with terpenes in acetonitrile were determined: (2.93±0.48)×109 M−1 s−1 (α-pinene), (2.86±0.35)×109 M−1 s−1 (β-pinene), and (1.40±0.12)×109 M−1 s−1 (limonene). The rate coefficients were found to be lower than previous measurements in the gas-phase, which we attribute to the onset of a diffusion-controlled limit to the reaction rate in solution.