title: Picosecond investigation of the collisional deactivation of OH A 2Sigma+(v' = 1, N' = 4, 12) in an atmospheric-pressure flame.
abstract: The collisional deactivation of the laser excited states A 2Sigma+(v' = 1, N' = 4, 12) of OH in a flame is studied by measurement of spectrally resolved fluorescence decays in the picosecond time domain. Quenching and depolarization rates, as well as vibrational energy-transfer (VET) and rotational energy-transfer (RET) rates are determined. An empirical model describes the temporal evolution of the quenching and VET rates that emerge from the rotational-state relaxation. Fitting this model to the measured 1-0 and 0-0 fluorescence decays yields the quenching and VET rates of the initially excited rotational state along with those that correspond to a rotationally equilibrated vibronic-state population. VET from the higher rotational state (N' = 12) shows a tendency for resonant transitions to energetic close-lying levels. RET is investigated by analysis of the temporal evolution of the 1-1 emission band. The observed RET is well described by the energy-corrected sudden-approximation theory in conjunction with a power-gap law.
authors.affiliation: General Energy Research, Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Beaud
authors.forename: P P
authors.initials: PP
authors.lastname: Radi
authors.forename: D
authors.initials: D
authors.lastname: Franzke
authors.forename: H M
authors.initials: HM
authors.lastname: Frey
authors.forename: B
authors.initials: B
authors.lastname: Mischler
authors.forename: A P
authors.initials: AP
authors.lastname: Tzannis
authors.forename: T
authors.initials: T
authors.lastname: Gerber