Investigation of molecular relaxation in SF6 by the amplitude-modulated wave method

A description is given of a new nonlinear spectroscopic method for obtaining narrow resonances in a Doppler absorption profile: the method of one amplitude-modulated laser wave. It is shown theoretically that narrow resonances in the line profile obtained by this method are deeper than those in the case of now-traditional methods of identically directed waves from two lasers. The requirements in respect of the laser frequency stability are not as stringent as in the two-laser case and variation of the frequency of one of the lasers is replaced by variation of the modulation frequency. The results are reported of an experimental investigation of the mechanism of relaxation in SF₆ at various pressures, carried out using amplitude-modulated radiation from one CO₂ laser. The resonance half-width is found to rise linearly with the pressure in the range 30–300 mTorr at a rate of 4 MHz/Torr. These experimental results confirm the collision mechanism proposed earlier.