Trevor C. Brown

Vibrationally excited populations from IR‐multiphoton absorption. II. Infrared fluorescence measurements

Infrared emission spectra were obtained for 1, 1, 2‐trifluorethane (TFE) excited by infrared multiphoton absorption (1079.85 cm−1). The emission features show that the HF reaction product is formed in vibrational states up to about v=3. Furthermore, emission attributed to F–C≡C–H was observed near 3320 cm−1, indicating that the difluoroethylene primary products of TFE decomposition undergo secondary photolysis; since the difluoroethylene products at room temperature do not absorb laser light, they must be formed vibrationally excited. The emission from the C–H stretch modes of TFE was readily identified near 2980 cm−1 and the emission intensity was obtained as a function of laser fluence. These data are in excellent agreement with predictions based on the theoretical expression for fluorescence intensity and the reconstructed populations determined by the Master Equation calculations described in the preceding paper. These results provide additional support for the accuracy of the reconstructed population...

Vibrationally excited populations from IR‐multiphoton absorption. I. Absorbed energy and reaction yield measurements

The molecule 1,1,2‐trifluroethane (TFE) was used in experiments to determine the population distribution of excited molecules produced by infrared multiphoton absorption induced by high power TEA CO2 lasers operating at 1079.85 cm−1 [9.6 μm R(22) line]. Optoacoustic measurements of absorbed laser power provided a measure of the mean energy of the population distribution, while very low pressure photolysis measurements of the collision‐free decomposition yield gave information about the high‐energy tail of the distribution. The experimental results were accurately simulated using a Master Equation model that incorporated Quack’s statistical–dynamical theory of infrared multiphoton absorption (cases B and C), RRKM unimolecular reactions (three channels), and collisional energy transfer. The computer simulations included known TFE molecular properties and only four adjustable parameters, which were very highly constrained in order to fit the experimental data. From the simulations, we conclude that the optic...