Absolute photoionization cross sections of the primary photofragments of chlorine dioxide and dichlorine monoxide

Photoionization of the primary photofragments of chlorine dioxide (OClO) an d dichlorine monoxide (Cl2O) is reported. The nascent photofragments are fo rmed by UV photolysis, they are subsequently photoionized by time-correlate d XUV laser radiation and finally detected by time-of-flight mass spectrome try. Primary photolysis of OClO leads to the formation of ClO + O at lambda = 359.5 nm, whereas ClO + Cl are formed by photolysis of Cl2O at lambda = 250 nm. The XUV photoionization of the photolysis products relies on single photon ionization. This allows to derive partial photoionization cross sec tions of the parent cations and their photolysis products from mass spectra l intensities by using the absolute photoionization cross sections of the a tomic products for calibration. Specifically, we obtain for OClO at E = 13. 74 eV: sigma(ClO) = 27 +/- 5 Mb and sigma(OClO) = 18.5 +/- 3 Mb. Consistent findings are obtained from equivalent experiments on Cl2O. The present res ults are compared with previous photoionization work on ClO and OClO to dem onstrate the reliability of UV-pump/XUV-probe spectroscopy.