Induced autoionization-like resonances in nonlinear third- and fifth-order susceptibilities of sodium vapor

A study was made of the influence of autoionization-like resonances in the continuum, induced by strong optical radiation, on the nonlinear susceptibilities governing third harmonic generation and the optical activity of sodium vapor. It was demonstrated experimentally for the first time that it should be possible to study high-lying states of atoms and molecules by the method of nonlinear polarization spectroscopy of the fifth-order optical nonlinearity. The experimental results were compared with the theory. An analysis was made of the feasibility of using this effect for spectroscopy of the states in the continuum and for generation of short-wavelength radiation in gaseous media.