Investigation of long-lived states in a gas by means of coherent nonstationary spectroscopy

Methods of coherent echo spectroscopy are employed to experimentally invest igate long-lived states that arise in an SF6 gas under the action of polari zed infrared resonant radiation and that are associated with polarization m oments of levels degenerate of the magnetic quantum number. It is demonstra ted that, for high pressures of the working gas and buffer He and Xe specie s, the inelastic channel provides a dominant contribution to the collisiona l relaxation of polarization moments. For a low-pressure SF6 gas, the decay rate of the echo signal decreases with the growth in the delay time betwee n pumping pulses, which is associated with the increase in the contribution of molecules with small radial velocity projections to the coherent respon se. The existence of this effect gives grounds to believe that long-lived s tates with lifetimes limited by the radiative lifetime can be detected.