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SYLA: Symposium Laboratory Astrophysics
SYLA 2: Laboratory Astrophysics
SYLA 2.1: Hauptvortrag
Montag, 14. März 2022, 16:30–17:00, Audimax
State-to-State Rate Coefficients for NH3-NH3 Collisions obtained from Pump-Probe Chirped-Pulse Experiments — •Christian P. Endres1, Paola Caselli1, and Stephan Schlemmer2 — 1MPI für extraterrestrische Physik, Garching, Germany — 2Universität zu Köln, Köln, Germany
The kinetics of rotational inelastic NH3-NH3 collisions is studied using pump-probe experiments, which are carried out with a Ku-band waveguide chirped pulse Fourier transform microwave spectrometer by observing the ammonia inversion doublets in the ground vibrational state. The population of one ammonia inversion doublet of a single rotational state is altered by a resonant pump pulse. Due to collisions, the resulting deviation from thermal equilibrium propagates to other states and is interrogated by probe pulses as a function of the pump-probe delay time. The bandwidth of the spectrometer allows to probe the intensity of many inversion transitions within a single chirped pulse excitation (probe pulse) on sub-microsecond timescales as a function of the pump pulse conditions. State-to-state rates are obtained by simulations of all coupled states fitted to the temporal behavior of the complete pump probe experiments where many individual (J,K) rotational states are addressed step by step by separate pump pulse sequences.