Pathway studies in Si(2p) inner-shell processes of H2Si(CH3)(2) by mass spectrometry and the photoion - Photoion coincidence method in the range 24-133 eV

Dissociative multiple photoionization processes of dimethylsilane (H2Si(CH3 )(2)) have been investigated in the valence and Si(2p) core level photoexci tation/photoionization regions by time-of-flight (TOF) mass spectrometry co upled to synchrotron radiation, operated in both the photoelectron-photoion coincidence (PEPICO) and photoion-photoion coincidence (PIPICO) modes. Two group absorption bands below and above the Si(2p(3/2)) threshold 106.51 eV are observed in both total photoion and PIPICO yield waves. Various monoca tions of H-n(+)(n = 1-3), CHn+(n = 0-4), C2Hn+(n = 1-3), SiC2Hn+(n = 0-3), SiCHn+(n = 0-5), SICHn+(n = 0-7) are observed. the yields depending on the excitation energy. In the valence ionization region, especially E < 30 eV, extrusions of H, H-2, CH3, and of CH4 (or H + CH3) and CH3 + H-2 (or H + CH 4), are predominantly observed leading to the formation of SiC2Hn+ (n = 6, 7) and SiCHn+(n = 3-5), respectively, whereas in the Si(2p) excitation and ionization regions, ionic fragments of smaller masses such as H+, CH3+, Si, and SICH3+ are relatively abundant in the PEPICO spectra. Bond-selective fragmentation processes occur in the two absorption regions. An ab initio c alculation was also carried out to predict discrete excitation energies and their modes corresponding to the transitions from the core to valence and Rydberg orbitals.