MULTIPLE IR PHOTON LASER-INDUCED REACTIONS OF CYCLOPROPANE

The multiple photon IR laser induced reactions of cyclopropane resulting from excitation of either of two fundamental vibrational modes has been demonstrated. In each case the products are typical of those formed with thermal excitation but the relative yields are not. The yield of the lowest energy barrier channel, isomerization, relative to higher channels, fragmentation, is dependent on the mode excited. Excitation of the C-H asymmetric stretch at 3.22 μm produces propylene with almost no fragmentation; excitation of the CH 2 wag at 9.50 μm produces roughly equal yields of propylene and fragmentation products. Collisions play a critical role in this process. At 3.22 μm, the effect of collisions with argon is to increase yields of the fragmentation channel. As these collisions cannot add any significant amount of energy to the cyclopropane, it is concluded that the upper channel is opened due to intermode vibrational energy redistribution. At 9.50 μm, argon tends to favor the lower energy pathway. These results are consistent with an excitation that is initially nonstatistical or mode selective. © 1979 American Institute of Physics.