Quantitative analysis of third harmonic generation of XUV radiation in a cell and a cw free jet of carbon monoxide

摘要

In the theory, the twohyphen;photon resonant thirdhyphen;order nonlinear susceptibility of a molecular gas is calculated. The variations of this susceptibility, with the rotational quantum numbers of the resonant states, are given in the case of two singlet states of different symmetries, Sgr; and Pgr;. In the experiment, third harmonic generation of XUV light (94.5ndash;97.5 nm) is obtained with and without twohyphen;photon resonance. The gaseous nonlinear medium is formed by CO as used either in a cell, or in a continuous supersonic free jet zone of silence. The intensity of the third harmonic wave generated is well related to the laser power, phasehyphen;matching conditions, twohyphen;photon resonances, and rotational temperature, through the nonlinear susceptibility, as described theoretically.