(CH3)3COOH (tert-butyl hydroperoxide): OH reaction rate coefficients between 206 and 375 K and the OH photolysis quantum yield at 248 nm

Abstract

Rate coefficients, k, for the gas-phase reaction of the OH radical with (CH₃)₃COOH (tert-butyl hydroperoxide) were measured as a function of temperature (206–375 K) and pressure (25–200 Torr (He, N₂)). Rate coefficients were measured under pseudo-first-order conditions using pulsed laser photolysis to produce OH and laser induced fluorescence (PLP–LIF) to measure the OH temporal profile. Two independent methods were used to determine the gas-phase infrared cross sections of (CH₃)₃COOH, absolute pressure and chemical titration, that were used to determine the (CH₃)₃COOH concentration in the LIF reactor. The temperature dependence of the rate coefficients is described, within the measurement precision, by the Arrhenius expression k₁(T) = (7.0 ± 1.0) × 10⁻¹³ exp[(485 ± 20)/T] cm³ molecule⁻¹ s⁻¹ where k₁(296 K) was measured to be (3.58 ± 0.54) × 10⁻¹² cm³ molecule⁻¹ s⁻¹. The uncertainties are 2σ (95% confidence level) and include estimated systematic errors. UV absorption cross sections of (CH₃)₃COOH were determined at 185, 214, 228, and 254 nm and over the wavelength range 210–300 nm. The OH quantum yield following the 248 nm pulsed laser photolysis of (CH₃)₃COOH was measured relative to the OH quantum yields of H₂O₂ and HNO₃ using PLP–LIF and found to be near unity.