Abstract

This paper- describes experimental and theoretical studies of narrow resonances observed in four-wave nixing spectroscopy (4WM) of Doppler broadened systems. In a simple "two level system, narrow resonances are not; observed if the system is closed, i.e., if population is conserved (with the exception of an overall decay constant- due to transit time effects.) However, narrow resonances can be observed when the system is open. These resonances can be attributed to radiative decay of the upper level to a state other than the ground state. The resonances can also be collision Induced tine to state changing or velocity changing collisions. The width of the resonance is determined by the transit time and usually results in a spike In the 4WM response. However, in a closed two-level system characterized by Magnetic degeneracies, narrow resonances can still be observed due to nonconservation of alignment and orientation. Moreover, the sign of this contribution depends on the specifics of the transition and can result in the observation of either a narrow dip or a narrow spike in the 4 WM spectrum.

© 1988 Optical Society of America