title: Doppler-Resolved Kinetics of Saturation Recovery.
abstract: Frequency-modulated laser transient absorption has been used to monitor the ground-state rotational energy-transfer rates of CN radicals in a double-resonance, depletion recovery experiment. When a pulsed laser is used to burn a hole in the equilibrium ground-state population of one rotational state without velocity selection, the population recovery rate is found to depend strongly on the Doppler detuning of a narrow-band probe laser. Similar effects should be apparent for any relaxation rate process that competes effectively with velocity randomization. Alternative methods of extracting thermal rate constants in the presence of these non-thermal conditions are evaluated. Total recovery rate constants, analogous to total removal rate constants in an experiment preparing a single initial rotational level, are in good agreement with quantum scattering calculations, but are slower than previously reported experiments and show qualitatively different rotational state dependence between Ar and He collision partners. Quasi-classical trajectory studies confirm that the differing rotational state dependence is primarily a kinematic effect.
authors: †Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States.
authors: Damien
authors: D
authors: Forthomme
authors: †Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States.
authors: Michael L
authors: ML
authors: Hause
authors: †Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States.
authors: Hua-Gen
authors: HG
authors: Yu
authors: ‡Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States.
authors: Paul J
authors: PJ
authors: Dagdigian
authors: †Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States.|§Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States.
authors: Trevor J
authors: TJ
authors: Sears
authors: †Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States.
authors: Gregory E
authors: GE
authors: Hall