Photoionization mass spectrometry of chlorine oxides

Photoionization mass spectrometry of four chlorine oxides (Cl2O, Cl2O4, Cl2 O6, and Cl2O7) is reported. Photoionization efficiency curves of parent and fragment ions are measured in the energy regime between 10 and 21 eV using monochromatic synchrotron radiation. Ionization energies (IE) of the chlor ine oxides and fragmentation appearance energies (AE) are obtained from pho toion yield curves of mass-selected cations. Specifically, we obtain IE(Cl2 O) = 10.88 +/- 0.02 eV, IE(Cl2O4) = 11.23 +/- 0.05 eV, IE(Cl2O6) = 12.66 +/ - 0.05 eV, and IE(Cl2O7) = 12.15 +/- 0.05 eV. The experimental results are used to derive numerous thermochemical stability data of the neutral and io nic chlorine oxides and their fragments, as well as plausible cation fragme ntation mechanisms. Resonant excitation with tunable vacuum ultraviolet rad iation is applied in the case of Cl2O to obtain further insight into autoio nization processes. Three series of Rydberg excitations are assigned conver ging to the (C) over bar((2)A(2)) ionization energy at 12.74 eV. (C) 1999 E lsevier Science B.V.