QUANTUM BEAT SPECTROSCOPY OF DIATOMIC TRANSIENTS

Abstract

Quantum beat spectroscopy is a method for sub-Doppler spectroscopy which provides lifetime limited linewidths and so is ideally suited to the precise measurement (typically +/- 0.1 MHz) of small splittings $(<100 MHz)$. Quantum beat spectroscopy has been applied for the first time to $^{3}\Pi$ states of transient diatomics. The reactive species are produced in a supersonic free jet using a electric discharge and quantum beats observed between hyperfine levels or Zeeman split levels from a small applied magnetic field. Magnetic g factors, including their vibrational dependence, have been determined from the Zeeman beats for both the $A^{3}\pi - X^{3}\Sigma$ transition of NH and the $B^{3}\pi - A^{3}\Sigma$ transition of ${N_{2}}^{\infty}$. A perturbation in the higher vibrational levels of NH was observed to have a strong effect on the Zeeman tuning.