Photodissociation dynamics of reactive species

In this project we investigate the photochemistry of halogen-containing radicals. These molecules are of considerable interest in atmospheric chemistry because of their role in the catalytic reactions leading to the stratospheric ozone destruction. Due to the high reactivity of the radicals, we perform the experiments in the gas phase. We utilize a pulsed valve in order to generate a molecular beam. A suitable precursor is expanded into the vacuum through an electrically heated SiC tube, which leads to the pyrolysis of the precursor, generating the desired radical. The reactions of the isolated radicals are subsequently studied with nanosecond lasers. One laser excites the radicals into a dissociative state and a second laser then ionizes the resulting photofragments. The ionized fragments are then detected by time-of-flight mass (tof) spectrometry, allowing to identify of the photodissociation products. A phosphor screen mounted behind the detector of the tof spectrometer enables us to measure the spatial distribution of the fragments. Analysis of the data yields the kinetic energy distribution of the fragments and in turn gives us insight into the photodissociation mechanism of the investigated radicals.