Transient-Nutation Effects in Time-Resolved Infrared-Microwave Double Resonance of Ammonia

Abstract

Transient nutation is observed in the time-resolved infrared-microwave double resonance of ammonia. This behavior is described by a Bloch equation for relaxation of the ammonia inversion levels, with an effective ${T}_{2}$ cross section of 400 \ifmmode\pm\else\textpm\fi{} 50 ${\mathrm{\AA{}}}^{2}$. A similar effect was produced by rapidly switching the Stark field applied to the molecules, which suddenly brings them into resonance with the cw microwave radiation.