Photoionization mass spectrometric study of Si2H6

Abstract

The adiabatic I.P. of Si2H6 obtained by a photoionization mass spectrometric study at two temperatures is 9.74±0.02 eV. The first fragment, Si2H+4, initially appears with a shallow slope at ≤10.04±0.02 eV, and with a much steeper slope at ≤10.81±0.02 eV. It is argued that the initial onset corresponds to formation of H2SiSiH+2, while the steeper onset is attributed to formation of H3SiSiH+. The second fragment, Si2H5, has an appearance potential of ≤11.59±0.02 eV (11.41±0.03 is a probable value). Successive decomposition leads to Si2H+2 (from Si2H+4 ) and Si2H+3 (from Si2H+5 ). The photoion yield curve for Si2H+3 also displays shallow and steep onsets. Upper limits for the appearance potentials can be readily extracted, but the true thermochemical onsets are less well defined. Heats of formation (or upper limits) are presented for each of these species. For Si2H+6, Si2H+5, and Si2H+4, the experimental values are in good agreement with recent ab initio calculations. For the daughter species, the experimental values exceed the calculated ones, as expected.

Cross‐Sections, Rate Constants and Transport Coefficients in Silane Plasma Chemistry

“…Work function of bulk crystalline silicon from CRC Handbook of Chemical Physics [59] BERKOWITZ et al [I751 (experimental) RUSCIC and BERKOWITZ [176] (experimental) derived from thresholds of photoelectron spectra recorded by BOCK et al [177]. When applied to the SiH4 and SizH6 spectra this method gives adiabatic IP in excellent agreement with the values measured by RUSCIC and BERKOWITZ RUSCIC and BERKOWITZ [178] (experimental) CURTISS et al…”

Quantum Monte Carlo binding energies for silicon hydrides

“…The atomization energy of Si 3 H 8 is derived from the result of Gunn and Green, 36 who give ⌬H f 0 ͑Si 3 H 8 , Tϭ298 K͒ϭ25.9 kcal/mol. For consistency, this was corrected by 3 kcal/mol on the assumption that the final state of the Si is amorphous, as was done in the JANAF tables for SiH 4 and by Ruscic and Berkowitz 35 for Si 2 H 6 . From the 298 K enthalpy of Si 3 H 8 computed with our scaled SCF vibrational frequencies, and the JANAF enthalpies of the reference states, crystalline Si and H 2 gas, we derive a correction to Tϭ0, obtaining ⌬H f 0 ͑Si 3 H 8 ,Tϭ0͒ϭ33.9 kcal/mol.…”

Infrared spectrum of the disilane cation (Si2H6+) from Ar-tagging spectroscopy

“…The low-resolution photoelectron spectrum exhibits a progression in the symmetric SiH 3 umbrella mode measured to be n 2 (a 1g ) B 0.11 eV, which corresponds to B900 cm À1 . 45,46 The current calculations predict for this mode a significantly lower frequency of only B800 cm À1 (817 and 787 cm À1 at the MP2 and B3LYP level, respectively). As the vibrational assignment is probably correct and the calculations are accurate to better than AE20 cm À1 , the discrepancy is probably due to the large uncertainty in the photoelectron measurement arising from the low spectral resolution.…”

“…44,45 The only vibrationally resolved feature that has been assigned to the symmetric SiH 3 umbrella mode is n 2 (a 1g ) B 0.11 eV (B900 cm À1 ). 45,46 Photoionization mass spectrometry of Si 2 H 6 yields an adiabatic ionization potential of AIE = 9.74(2) eV, and low appearance energies of r10.04(2) and r10. Corresponding geometrical, vibrational, and energetic parameters are listed in Tables 1 and 2.…”