Research Group Prof. Dr. G. Friedrichs

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SLS Oct 19October 2019: Nine full days of beamline time at the Swiss Light Source (Villigen, CH) have been granted to quantify the wavelength dependent yield of molecular chlorine (Cl2) from UV photolysis of oxalyl chloride ((COCl)2). 24h/day operation of the experiment required a strong team consisting of Nancy Faßheber, Gernot Friedrichs, Sebastian Hesse, Yasuyki Sakai (Univ. Fukui, Japan), Michael Stuhr, and Marcel Wohler.

Oxalyl chloride is a widely used precursor for Cl atoms to initiate photochemical generation of hydrocarbon radicals for reaction kinetics studies. A recently published paper, however, has reported unexpected and high direct Cl2 formation from the UV photolysis of oxalyl chloride, hence challenging the results of several previous studies. The aim of our experiment was to use the versatile PEPICO setup (photoelectron photoion coincidence mass spectrometry) at the VUV beamline in combination with UV laser photolysis at wavelengths of 355, 248 and 213 nm to quantifiy the photolysis products. Indeed, direct formation of Cl2 has been observed. Now, a detailed analysis of the extensive data set and supplemental ab initio quantum chemical calculations are needed to fully assess the experimental outcome.