Multiphoton satellites in the saturated-absorption Spectrum of SiF4 gas

A saturated-absorption spectrum of SiF4 gas, free of Doppler broadening, has been recorded in the lasing range of a low-pressure CO2 laser. Multiplets of superfine structure are observed, which are due to the tunnel transitions between the states of molecular rotation around equivalent symmetry axes. Multiplet satellites are revealed, whose origin is explained by two-photon processes. Splitting of the energy levels of the superfine structure multiplet is derived from satellite interpretation. A satellite is found, which can be caused by fourphoton processes.