Some characteristics of spectra of multiphoton absorption in SF6 under conditions of essentially collisionless excitation of the molecules by CO2 laser pulses

A study was made of the multiphoton absorption spectra of a molecular SF₆ beam at various vibrational and rotational temperatures, and also of molecules of the same compound in a cell kept at room temperature but at a fairly low gas pressure (8.5 mTorr). An increase in the excitation energy density (in the range 0.1–3.0 J/cm²) did not increase the "red shift" of the multiphoton absorption spectra. The position of the maximum and the width of the spectrum were governed mainly by the vibrational temperature, i.e., by the initial distribution of molecules between the vibrational states.