Photoionization mass spectrometric studies of SiHn(n=1ndash;4)

摘要

A photoionization mass spectrometric study of SiH4atT=150 K reveals the presence of SiH+4with an adiabatic threshold at 11.00plusmn;0.02 eV. The implications for the structure of this Jahnndash;Teller split state are discussed. The appearance potentials of SiH+2and SiH+3are 11.54plusmn;0.01 eV and le;12.086 eV, respectively. The reaction of F atoms with SiH4generates SiH3(Xthinsp;2A1), SiH2(Xthinsp;1A1andathinsp;3B1), and SiH (Xthinsp;2Pgr;) in sufficient abundance for photoionization studies. The measured adiabatic ionization potentials (eV) are: SiH3, 8.01plusmn;0.02; SiH2(Xthinsp;1A1), 9.15plusmn;0.02 or 9.02plusmn;0.02; SiH2(athinsp;3B1), 8.244plusmn;0.025; SiH, 7.91plusmn;0.01. The singletndash;triplet splitting in SiH2is either 0.78plusmn;0.03 or 0.91plusmn;0.03 eV. The dissociation energy of SiH is 2.98plusmn;0.03 eV. A Rydberg series is observed, converging to SiH+(athinsp;3Pgr;) at 10.21plusmn;0.01 eV. Heats of formation of the various neutral and ionic species are presented, as are the stepwise bond energies of SiH4.