Ionic pathway studies in fragmentation of the core-excited (CH 3) 3SiBr molecule involving the Br(3d) and Si(2p) inner-shells in the range of 60–133 eV

Abstract

Dissociative multiple photoionization of bromotrimethylsilane [(CH 3) 3SiBr] has been probed in the valence, the Br(3d), and the Si(2p) core-level photoexcitation/photoionization regions by time-of-flight (TOF) mass spectrometry and photoion–photoion coincidence (PIPICO) method together with linearly polarized synchrotron radiation. The inner-shell photoionization spectra are dominated by a huge resonance attributed to the diffusion of the outgoing photoelectrons by the centrifugal barrier for the Br(3d 9 ϵf ) outgoing channel. In addition to the giant resonance, discrete photoabsorption bands below the Br(3d 5/2) and Si(2p 3/2) thresholds have been observed in both the total photoion and PIPICO yield spectra. In the valence excitation/ionization region, single ionization leading to the formation of C n H p SiBr +( n=0–3), C n H p Si +( n=0–3), and CH 3 + prevails. Above the Br(3d) threshold including the Si(2p) region, however, destruction of the three or more bonds could account for the dominant PIPICO channels leading to the formation of H +–CH p +( p=1–3) and CH n +–H p Si +( p=0,1) ion pairs. The exclusive formation of only the singly charged ions over the entire energy range indicates that charge redistribution is much faster than the bond cleavages.