Diode Laser Spectroscopy of the Dynamics of Multiphoton Excitation of SF6 Molecules by CO2 Laser Pulses

Abstract

The dynamics of excitation by CO2 laser pulses of SF6 molecules from individual rotational sublevels J″ of the ground vibrational state have been investigated in a pulsed molecular jet under essentially collisionless conditions. At different energy fluences of exciting laser pulse Φ = 10−5 + 10−1 J/cm2, the dependences of the fraction fJ of excited molecules on the rotational quantum number J″ have been obtained, when SF6 molecules were excited on the 10P(16) CO2 laser line, as well as on the 10P(18) and 10P(14) lines at Φ = 0.1 J/cm2. Comparison of experimental results with theoretical predictions18–20 shows rather strong disagreement between theory and experiments both in the population of the υ3 = 1 state and in the role of multiphoton transitions. It is shown that the narrowing of the exciting laser pulse spectrum (the 10P(16) line, Φ ≲ 10−2 J/cm2) results in drastic decrease of the fraction of excited molecules from the (υ3 = 0, J″ = 4) state which is most resonant with laser radiation.