A multi-coincidence study of the double, triple photoionization and fragmentation of the SiF_4 molecule around the Si 2p edge

摘要

Multiple ionization of the SiF_4 molecule has been studied using synchrotron radiation and time-of-flight mass spectrometry in a multi-coincidence mode, in the photon energy range of 70-109.4 eV, which encompasses the Si 2p edge. Photoionization branching ratios have been measured under efficient ion extraction and the results are compared to previously published data. Two electron-ion coincidence techniques (PE2PICO, and PE3PICO) have been used in the elucidation of the fragmentation mechanisms of highly excited molecular ions, formed following the absorption of a high-energy photon. It is shown that the unstable doubly charged parent molecule, SiF_4~(2+), fragments preferentially (90%) via the asymetric mechanism m~(2+) → m_1~(2+) + m_2.