11128-24-8Relevant academic research and scientific papers
Rotational state-specific dynamics of SiF C2Δ-B2Σ+ collision-induced transfer
Jackson, Neil A.,Randall, Colin J.,McKendrick, Kenneth G.
, p. 51 - 59 (1998)
Laser excitation on the C2Δ-X2Π transition was used to prepare discrete rotational levels of the SiF C2Δ, υ = 0 state, allowing their state-specific collisional behavior to be investigated. Time- and wavelength-resolved returning C-X fluorescence spectra established that the initial populations were only partially perturbed by rotationally inelastic processes within the C2Δ state at the typical pressures of our experiments. Transfer within the F1 manifold appears to be favored by a factor of ～2 over transfer from F1 to F2. There is relatively little dependence on rotational state (in the range j = 2.5-21.5) of the rate constant for total collisional removal of the C2Δ state by either H2 or N2. As previously established, a fraction of the collisionally removed population is deposited in the lower-lying B2Σ+ state. Dispersed B-X fluorescence spectra revealed broad rotational distributions in the predominant B2Σ+, υ′ = 0 product level in collisions with H2 and N2, indicating substantial release of rotational energy during the transfer between electronic states. There is a positive correlation between the peak and average product j′ and the initial rotational state j. The main features of the observed behavior are reproduced by a limiting impulsive model. We believe this to be a consequence of the respective valence and Rydberg characters of the C2Δ and B2Σ+ states.
Absolute cross sections for electron-impact ionization and dissociative ionization of the SiF free radical
Hayes, Todd R.,Wetzel, Robert C.,Baiocchi, Frank A.,Freund, Robert S.
, p. 823 - 829 (1988)
Absolute cross sections for electron-impact ionization of the SiF free radical from threshold to 200 eV are presented for formation of the parent SiF+ ion and the fragment Si+ and F+ ions.A fast beam of SiF is prepared by charge transfer neutralization of an SiF+ beam.The radicals form in the ground electronic state and predominantly in their ground vibrational state, as shown by agreement of the measured ionization threshold with the ionization potential.The absolute cross section for SiF -> SiF+ at 70 eV is 3.90 +/- 0.32 Angstroem2.The ratio of cross sections for formation of Si+ to that for SiF+ at 70 eV is 0.528 +/- 0.024; the ratio for formation of F+ to that of SiF+ is 0.060 +/- 0.008.The observed threshold energy for Si+ formation indicates the importance of ion pair formation SiF -> Si+ + F-.Breaks in the cross section at 14.3 and 17 eV are assigned as dissociative ionization thresholds.
Matrix Reactions of SiH4 and GeH4 with F2. Infrared Spectra of Several HF Product Complexes
McInnis, Thomas C.,Andrews, Lester
, p. 5276 - 5284 (1992)
Silane and germane were condensed with F2 at high dilution in argon on a 13 +/- 1 K substrate.Weak product complexes produced on condensation and increased by ultraviolet photolysis are assigned to SiH3F..HF, SiH2..HF or SiH2..(HF)2, and HSiF..HF.Annealing produced new bands due to F atom reactions that are attributed to SiH3..HF.The GeH3F molecule was observed in the similar GeH3F..HF complex.H-F vibrations in these complexes suggest that F is more basic in GeH3F than in SiH3F owing to the more electropositive nature of germanium as compared to silicon.
LASER-INDUCED FLUORESCENCE SPECTROSCOPY OF SiF PRODUCED BY IR MULTIPLE-PHOTON DISSOCIATION OF SiF4
Popov, V. K.,Rossberg, M.,Strube, W.,Wollbrandt, J.,Linke, E.
, p. 225 - 230 (1990)
Excitation spectra and dispersed fluorescence were measured in the β-system (B2Σ-X2?) of the SiF radical produced by multiphoton dissociation (MPD) of SiF4 with a TEA CO2 laser.Within the limits of error no effect of the wavelength of the photolysis laser on the spectra was found.Formation and decay kinetics of SiF during and after IR laser excitation, as monitored by LIF, are also presented.The temporal behaviour if the SiF LIF signal was different for different wavelengths of the CO2 laser.For wavelengths close to the linear absorption band there was no induction period in the formation of SiF.The pressure dependence of the kinetics was different for the two CO2 laser branches.
Large rotational energy release in collision-induced SIF C(2)Δ-B(2)Σ(+) valence-Rydberg transfer
Jackson, Neil A.,Watson, Cameron W.,McKendrick, Kenneth G.
, (1995)
Distinct rotational population distributions were prepared in SiF C(2)Δ, v=0 radicals by laser excitation. Collisions with H2 or N2 transferred a fraction of the C(2)Δ molecules to the lower-lying B(2)Σ(+) state. B-X fluorescence spectra revealed the nasc
THERMAL REACTIONS OF F2 AND NF3 WITH SILICON(110) STUDIED BY LASER IONIZATION MASS SPECTROMETRY
Squire, D. W.,Dagata, J. A.,Hsu, D. S. Y.,Dulcey, C. S.,Lin, M. C.
, p. 2827 - 2834 (1988)
The techniques of laser and electron ionization mass spectrometry have been employed to study the thermal etching of Si(110) by F2 and NF3 at substrate temperatures between 300 and 1200 K.By two-photon resonance-enhenced ionization of SiF2 via the B1B2 state, the apparent activation energy for gaseous silicon difluoride production was found to be 8.9+/-0.3 and 22.1+/-1.7 kcal/mol for F2 and NF3, respectively.SiF was not detected.An extensive search for SiF3 during etching by F2 at 1000 K, by means of resonance ionization from 320 to 325 and from 416 to 510 nm, also showed no signs of the species.Both SiF and SiF3 are thermochemically unimportant etch products under the conditions employed.In F2 etching, SiF4 and total silicon fluoride ΣSiFx+ signals as measured by electron ionization rose rapidly at lower temperatures and stabilized between 700 and 900 K before rising again.No such behavior was observed for SiF2 production from F2 or for the products formed in NF3 etching.Apparent activation energies for total silicon fluoride and SiF4 production are similar.For F2, they were found to be abaut 9 kcal/mol in the low-temperature region, and for NF3 both were measured to be abaut 21 kcal/mol.A proposed reaction mechanism explaining these and related results is discussed.
Energetics and dynamics in the reaction of Si+ with SiF4. Thermochemistry of SiFx and SiF+x (x=1, 2, 3)
Weber, M. E.,Armentrout, P. B.
, p. 6898 - 6910 (2007/10/02)
The title reaction is studied using guided ion beam mass spectrometry.Absolute reaction cross sections are measured as a function of kinetic energy from thermal to 40 eV, and three endothermic product channels are observed.The dominant SiF+ + SiF3 channel is only slightly endothermic, while the SiF3+ + SiF and SiF2+ + SiF2+ channels have much higher thresholds.The SiF3+ cross section magnitude is about half that of SiF+, while the SiF2+ cross section is an order of magnitude smaller than that of SiF+.A second feature which appears in the SiF2+ cross section is due to dissociation of SiF3+ .There is evidence that SiF+ and SiF3+ are produced via a direct mechanism.Competition between these two channels is interpreted in terms of molecular orbital correlations and qualitative potential energy surfaces.One surface is found to correlate only with the SiF3+ + SiF channel, while another correlates diabatically with this channel and adiabatically with the SiF+ + SiF3 channel.Competition on this latter surface has an energy dependence which is consistent with the Landau-Zener model.Reaction thresholds are analyzed to yield 298 K heats of formation for SiFx and SiFx+ species.From an evaluation of these and literature values, we recommend the following values:.
