Valence-level photofragmentation of gaseous Si(CH3)Cl-3 and solid-state analogs studied with synchrotron radiation

The dissociative photoionization channels of gaseous Si(CH3)Cl-3 and ion de sorption mechanisms of solid-state analogs following valence-level excitati on have been investigated by means of photoionization mass spectroscopy, th reshold photoelectron spectroscopy (TPES), and photon-stimulated ion desorp tion (PSID) using synchroton radiation. The adiabatic ionization threshold of the parent molecular ion was determined to be 11.18 eV, consistent with the value of 11.16 eV obtained from the TPES spectrum. An energy shift simi lar to 0.8 eV toward lower binding energies for the orbitals of solid Si(CH 3)Cl-3 with respect to the gas phase values was observed. Two thresholds at 14.97 and 17.51 eV in the CH3+ photoionization efficiency spectrum are pro bably associated with the ionization of 2e " and 11a(1) orbitals, respectiv ely. The H+ desorption threshold at 20.1 eV in the PSID spectrum may be att ributed to the excitation of C 2s electron correlation states to the unoccu pied states. The Cl+ desorption threshold at 19.9 eV is likely initiated by an Auger-stimulated desorption process. (C) 1999 American Institute of Phy sics. [S0021-9606(99)70731-2].