Oscillator strengths of the fundamental and overtone OH-stretching bands of tert-butyl hydroperoxide in gas phase

Abstract

We have recorded gas-phase room-temperature absorption spectra of t-BuOOH in the OH-stretching regions, $\Delta v_{OH}=1-5$, using a combination of Fourier transform infrared spectroscopy and cavity ring-down spectroscopy. The t-BuOOH samples are phase-extracted into dichloromethane, which can be accurately accounted for by spectral subtraction. We thereby obtain spectra of pure t-BuOOH and corresponding sample partial pressures allowing us to obtain absolute intensities of the OH-stretching bands in all regions. The subtraction of solvents and impurities provides accurate values for the band intensities and positions. A reduced dimensional local mode model is invoked to corroborate the experimentally determined band oscillator strengths and their assignments. The fundamental OH-stretching band oscillator strength is determined to be $(4.56\pm 0.15)\times 10^{-6}$ about twice as large as the literature value. In the $\Delta v_{OH}=5$ region, the intensity is spread out efficiently by a Franck–Condon-like mechanism to combination features associated with the OH-stretch and the COOH-torsion.