Fluorescence of cyclohexane vapor: pressure dependence and quenching studies

• Published in: The Journal of chemical physics 1986-09, Vol.85 (5), p.2445-2449
• Main Authors: WICKRAMAARATCHI, M. A, PRESES, J. M, WESTON, R. E. JR
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Exact sciences and technology; Intensities and shapes of molecular spectral lines and bands; Molecular properties and interactions with photons; Physics
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.451103

The pressure dependence of the fluorescence lifetime of cyclohexane vapor excited at wavelengths between 168.5 and 175.0 nm has been investigated. Due to the unusual dependence of the lifetime on cyclohexane pressure, a simple Stern–Volmer type of extrapolation cannot be used to obtain the collisionless lifetime at any of the excitation energies employed. Also, fluorescence decay curves fit a single-exponential function only under certain conditions of pressure and excitation wavelength. The rate constants for quenching of the excited state(s) by O2 at excitation wavelengths of 172.0 and 169.5 nm are (6.1±0.1)×10−10 and (7.9±1.4)×10−10 cm3 molecule−1 s−1, respectively. The difference between these rate constants is not significantly larger than the experimental uncertainty. At 172.0 nm, the rate constant for quenching by Xe is (7.1±0.3)×10−12 cm3 molecule−1 s−1. At this same excitation wavelength, quenching by He, Ar, and N2 is extremely small.