Intensity and Pressure Effects in Infrared Multiphoton Dissociation. Phitilysis of Hexafluoroacetone and Trifluoromethyl Bromide with 2-ns Laser Pulses

Article abstract of DOI:10.1021/j150609a015

We have carried out a study of the effect pulse length on the infrared multiphoton dissociation of hexafluoroacetone.A constant fluence of 1.8 J cm^-2 was used, for both short-pulse (2-ns fwhm) and long-pulse (ca. 120 ns fwhm, 5-μs tail, gain swithed, self-mode-locked TEA CO2 laser) irradiation.The dissociation yields are very significantly different both in their magnitude and in their dependence on pressure of substrate of of added hexafluoroethane.At moderate pressures (>0.2 torr) collisional effects dominate the long-pulse irradiation.Possible explanations of these effects are discussed.A study of the isotopically selective dissociation of trifluoromethyl bromide revealed that, although the intensity is high, isotopic selectivity (α ca. 20) is retained.