DISSOCIATIVE SINGLE, DOUBLE, AND TRIPLE IONIZATION FOLLOWING SI2P INNER-SHELL PHOTOEXCITATION OF SICL4

The multiple photoionization of SiCl4 has been investigated in the val ence and Si2p inner shell regions using time-of-flight mass spectromet ry and synchrotron radiation in the range 38 - 133 eV. The ion yield a nd the branching ratios are reported for charged species arising from the dissociative photoionization processes. Various monocations, such as Cl+, Cl2+, and SiCln+(n = 0 - 4), are observed together with doubly charged species such as Si2+, Cl2+, and SiCl2+. The photoion-photoion coincidence technique has been employed to investigate a variety of d issociation processes via Coulomb explosion and to elucidate the disso ciation mechanisms. Ion pairs of Si+ - Cl+ and SiCl+ - Cl+ are observe d dominantly in the Si2p edge. With the help of ab initio Hartree-Fock calculation, we estimated the term values and symmetries of the discr ete core-excited states and then predicted the Si2p discrete excitatio n energies. Also, the discrete excitation energies of Si2p in SiCl4 ar e compared with those in the isovalent species SiBr4. The variation of the ionic fragmentation as a function of photon energy is discussed i n conjunction with the relevant electronic states.