Photolysis Dynamics Laser Chemistry Lab

In one-photon dissociation of gaseous acetyl chloride at 248 nm, time-resolved Fourier-transform infrared emission spectroscopy is used to detect the fragments of HCl, CO, and CH2 in the presence of Ar or O 2. The high-resolution spectra of HCl and CO are analyzed to yield the corresponding internal energy deposition of 8.9 ± 1.1 and 6.2 ± 0.9 kcal/mol. The presence of the CH2 fragment is verified by detecting the CO2 product resulting from the reaction of CH 2 and the added O2. The probability of the HCl formation via a hot Cl reaction with the precursor is examined to be negligible by performing two experiments, the CH3COCl pressure dependence and the measurement of Br2 with Cl reaction. The HCl elimination channel under the Ar addition is verified to be slowed by 2 orders of magnitude, as compared to the Cl elimination channel. The observed fragments are proposed to dissociate on the hot ground electronic state via collision-induced internal conversion. A two-body dissociation channel is favored leading to HCl and CH2CO, followed by secondary dissociation. © 2010 American Chemical Society.