Effects of Reagent Translational and Vibrational Energy on the Dynamics of Endothermic Reactions

摘要

The endothermic reactions Br + CH sub 3 I implies CH sub 3 + IBr ( delta H sub 00 = 13 kcal/mole) and Br + CF sub 3 I implies CF sub 3 + IBr ( delta H sub 00 = 11 kcal/mole) have been studied by the crossed molecular beams method. Detailed center-of-mass contour maps of the IBr product flux as a function of recoil velocity and scattering angle are derived. For both systems it is found that the IBr product is sharply backward scattered with respect to the incident Br dirction, and that most of the available energy goes into product translation. Vibrational enhancement of the Br + CF sub 3 I reaction was investigated by using the infrared multiphoton absorption process to prepare highly vibrationally excited CF sub 3 I. At a collision energy of 31 kcal/mole (several times the barrier height), reagent vibrational energy appears to be less effective than an equivalent amount of (additional) translational energy in promoting reaction. More forward scattered IBr is produced in reactions of Br with vibrationally hot CF sub 3 I. (ERA citation 06:032623)