Rapid passage signals induced by chirped quantum cascade laser radiation: K state dependent-delay effects in the nu2 band of NH3.
In this Letter, a 10 microm quantum cascade laser operating in the intrapulse mode is used observe rapid passage (RP) effects within a 40 cm single-pass gas cell containing low pressures of NH(3). The laser tuning range allows the rotational states J=2 with K=0, 1, and 2 to be probed. We show that the RP structures change as a function of optical density and that the magnitude of the delay in the switch from absorption to emission as a function of increased gas pressure is dependent upon the initial value of K. These measurements are qualitatively well modeled using the Maxwell-Bloch equations.
Northern
J H
JH
Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK.
Ritchie
G A D
GA
Smakman
E P
EP
van Helden
J H
JH
Cockburn
J
J
Duxbury
G
G