Endres CP, Caselli P, Schlemmer S. State-to-State Rate Coefficients for NH
3-NH
3 Collisions from Pump-Probe Chirped Pulse Experiments.
J Phys Chem Lett 2019;
10:4836-4841. [PMID:
31403798 PMCID:
PMC6748673 DOI:
10.1021/acs.jpclett.9b01653]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 08/04/2019] [Indexed: 06/10/2023]
Abstract
The kinetics of rotational inelastic NH3-NH3 collisions are recorded using pump-probe experiments, carried out with a K-band waveguide chirped pulse Fourier transform microwave spectrometer, in which the population of one inversion doublet is altered by the pump pulse. Due to self-collisions, the resulting deviation from equilibrium propagates to other states and, thus, can be interrogated by probe pulses as a function of the pump-probe delay time. A clear hierarchy of the state-to-state collision processes is found and subsequently translated into propensity rules. State-to-state rate coefficients are estimated, first via an analysis of the kinetics, and then more robustly and accurately derived from the pressure-dependent measurements using a global fitting procedure.
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