Pressure and fluence dependence in the decomposition of cyclobutanone vaporby a pulsed CO2 laser

A re-examination of the decomposition of cyclobutanone vapor by a pulsed CO2 laser over a range of pressure and fluence has shown that the apparent disagreement in previous measurements of the pressure dependence of the C3H6/C2H4 product ratio can be explained by differences in absorbed energy density. At low pressures of cyclobutanone, the energy of the decomposing molecules is apparently higher at low fluence than at high fluence, and an explanation is suggested in terms of a variation in the relative proportions of "collision-modified" and "collision-free" reactions with changing pressure and absorbed energy density.