Nonlinear Spectroscopy Methods Research Articles

Investigation of elastic scattering by nonlinear spectroscopy methods

An analysis is made of the special features of diffraction effects in collisions between molecules. A hypothesis is put forward on the nature of the frequency shift of nonlinear resonances in rotational–vibrational transitions.

Investigation of molecular relaxation in SF6by 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.

Collision induced resonant four-photon parametric generation as a method of nonlinear spectroscopy

Generation of the combination tone ω v = 2 ω 0 − ω μ in the case where the nonlinear process is possible only in the presence of coherent reorienting collisions, is considered. A simple measurement method of the cross-section difference between “orientation” and “alignment” destruction is proposed.

Electric-field induced nonlinear coherent infrared spectroscopy investigation of the Q 01 (1) vibro-rotational mode of the H 2 molecule

A new method of nonlinear spectroscopy has been applied to the investigation of the Q 01 (1) (Raman active) transition of the H 2 molecule. The method has been applied to the first direct measurement of the T 2 coherence relaxation time in a gaseous medium, by a coherent Transient Free-induction decay effect.