SiO Molecules Research Articles

Electronic structure of defects at Si/SiO2 interfaces

After summarizing the essential features of an idealized model of the Si/SiO2 interface, we discuss first-principles EMTO calculations of the electronic structure of SiO2 supercells and Si/SiO2 superlattices containing periodic arrays of noninteracting localized defects. Among the defects investigated were Si and O interstitials and vacancies; interstitial O2, SiO, and H2O molecules; and substitutional Al-interstitial H complexes. As an application of these theoretical studies, we suggest an interpretation of the U-shaped continuum of localized interface states which is often derived from experimental measurements of suitably processed Si/SiO2 interfaces.

R-centroids and Franck-Condon factors of the SiO molecule

The r-centroids and Franck-Condon factors for the bands of the E 1σ + − X 1σ + and a 3πr − X 1σ + systems of the astrophysically important SiO molecule have been determined. The characteristics bands of this molecule are found in the sunspots. The Franck-Condon factors are determined by the approximate analytical method of Jarmain and Fraser. The absence of the bands in these systems is explained.

Detection of the SiO /v = 2, J = 2-1/ maser

Masers in one or more rotational transitions of the first three excited vibrational states of the SiO molecule have now been detected toward over 60 late-type Mira variables and supergiants and toward the infrared source IRc2 in the KL Nebula. The precise geometry and pump mechanism for the SiO masers, however, are not yet well understood. Buhl et al. (1974) found the v = 2, J = 2-1 transition to be undetectable in a search involving four stars, although similar transitions are usually strongly masing. A description is presented of the results of a sensitive search for this line in a number of late-type stars and Ori A, taking into account its final detection in Chi Cyg. The only detected SiO, v = 2 line maser star, Chi Cyg, has the largest known visual range of any Mira variable and is also one of the nearest (90 pc). It is one of the coolest stars yet identified, with an effective temperature of about 1800 K at minimum.

The infrared spectrum of SiO near 1240 cm −1 and its relation to the circumstellar SiO maser

The infrared absorption spectrum of the SiO molecule has been measured at temperatures between 1150 and 1350°C with a tunable diode laser. Transitions ranging from J″ = 0 to J″ = 60 and v″ = 0 and v″ = 4 have been measured. These measurements have been combined with microwave measurements made by other workers to yield a consistent set of Dunham ro-vibrational constants. The relation of the infrared absorption spectrum to inversion mechanisms for the circumstellar SiO maser is discussed.

Molecular emission from expanding envelopes around evolved stars. II - SiO - On the mechanism of mass loss and the efficiency of grain formation

The currently available body of data on SiO radio emission from circumstellar envelopes of late-type stars is presented and analyzed. Mass-loss rates of SiO molecules are derived and compared with total mass-loss rates suggested by other authors using independent considerations. The comparison implies that less than approx.1% of the available silicon is in the form of gas-phase SiO. It is concluded that the efficiency of incorporation of Si into grains is greater than approx.99%.Data on SiO and CO are used to examine the correlation between envelope expansion velocity and period of the underlying star. Our finding that carbon-rich and oxygen-rich stars both follow the same relation implies that the mechanism for mass loss in long-period variables is (1) independent of stellar rype or the C/O ratio, (2) independent of the constitution of grains, and (3) associated either directly or indirectly with pulsation.Also, data on CO and SiO emission in the same stellar envelopes are compared.

The Interaction Between the Electronic States G 1Π and I 1Π in the SiO Molecule

In the SiO spectrum the band systems G1Π-X1Σ+ and I1Π-X1Σ+ are situated in the spectral region 1300-1470 Å. The upper states perturb each other strongly. This paper contains a deperturbation calculation of the upper levels in Si16O and in Si18O. The isotopic shifts are also studied. The mutual interaction is treated in an adiabatic approximation and is found to increase linearly with v for near-degenerate vibrational G and I levels.

Theoretical study of the X1Σ+, A1Π, C1Σ− and E1Σ+ states fo the SiO molecule

The self-consistent-field plus configuration-interaction method has been used to compute potential energy curves and certain one-electron properties for the X1Σ+, C1Σ−, A1Π, and E1Σ+ states of SiO. This study employed a basis consisting of 51 Slater-type orbitals which is an expanded version of the one reported by McLean and Yoshimine. The computed ground-state dissociation energy (De) of 8.1 eV is in excellent agreement with the experimental value of 8.26±0.13 eV. The theoretical ground-state electric dipole moment function is in good agreement with the experimental curve constructed from the microwave data for the v=0–3 vibrational levels. Einstein A coefficients for vibration–rotation transitions computed from existing theoretical and experimental data are in good agreement. The E1Σ+ state is shown to dissociate adiabatically to ground-state atoms over a potential barrier with a maximum near 5 bohr. Calculated transition probabilities and radiative lifetimes for the A1Π–X1Σ+ and E1Σ+–X1Σ+ band systems agree well with recent laboratory experiments. Absorption cross sections as a function of wavelength have been computed and used to determine the opacity of SiO boundary layers that will form on the surface of probe vehicles entering the Jovian atmosphere at high speeds. These calculations demonstrate that the brilliant shock layer emission will be significantly absorbed by the SiO A1Π–X1Σ+ and SiO E1Σ+–X1Σ+ band systems in the boundary layer in the spectral region between 170 and 230 nm.

Constraints on the properties of circumstellar shells from observations of thermal CO and SiO millimeter line emission

view Abstract Citations (48) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Constraints on the properties of circumstellar shells from observations of thermal CO and SiO millimeter line emission. Lambert, D. L. ; Vanden Bout, P. A. Abstract An attempt to detect CO and SiO microwave emission from Betelgeuse and long-period variables (LPVs) is described. The absence of SiO 86 GHz emission from the Betelgeuse circumstellar shell is shown to require that either all Si is associated into silicate dust grains or SiO molecule formation is inhibited. The former explanation is consistent with published estimates of the column density of silicate grains. The latter explanation is supported by the absence of emission in the CO 115 GHz line. Circumstellar absorption lines are not present in the TiO y(0, 0) band near 7100 A. TiO, like SiO and CO, appears to be underabundant in the shell. The new detections of circumstellar microwave emission include an observation of the CO 115 GHz line from R Cas (the first LPV for which both SiO 86 GHz emission and CO 115 GHz emission are seen) and of the SiO 86 GHz line from the S star Cyg. The absence of the isotopic line 30SiO at 84 GHz shows that the shells around R Cas, R Leo, and Cyg have an optical depth in the 86 GHz line of r < 10. This suggests that the SiO molecules contain a minor fraction of the total Si and that a substantial fraction of the Si is in the silicate grains. The shell around R Leo has been detected through the K I fluorescent emission. This confirms that the shells are large. Subject headings: radio sources: lines - stars: abundances - stars: circumstellar shells - stars: long-period variables Publication: The Astrophysical Journal Pub Date: May 1978 DOI: 10.1086/156088 Bibcode: 1978ApJ...221..854L Keywords: Abundance; Millimeter Waves; Radio Sources (Astronomy); Stellar Envelopes; Thermal Emission; Variable Stars; Carbon Monoxide; Cosmic Dust; Granular Materials; Interstellar Matter; Silicon Oxides; Astrophysics; Carbon Monoxide:Circumstellar Shells; Circumstellar Shells:Long-Period Variables; Circumstellar Shells:M Supergiants; Circumstellar Shells:Sio; SiO: Circumstellar Shells full text sources ADS | data products SIMBAD (6)

The vacuum ultra-violet photoelectron spectrum of the SiO(X1Σ+) molecule

The vacuum ultra-violet photoelectron spectrum of the SiO(X1Σ+) molecule has been recorded and interpreted with the aid of both ab initio molecular orbital and multiple-scattering Xα calculations. Three bands have been observed with vertical ionization potentials of 11·61, 12·19 and 14·80 eV, corresponding to ionization to the X2Σ+, A2Π and B2Σ+ states of SiO+ respectively. Estimates of r e, and D e for these ionic states have been made.

Grain Formation in Nova Envelopes

Grain formation in ejected envelopes of novae is investigated. The solar abundance is assumed as one of the typical examples that C/O is smaller than unity. Then, magnesium silicate is proved to be the first main condensate. We estimate the number density c1 (t1) of monomers (SiO molecules for our case) at the beginning of condensation to beabout 105 cm for ΔM = 3 x 10-4 M⊙and Vexp = 1000 km sec-1 (ΔM is the ejected mass and V exp is the expansion velocity).

The true potential energy curves for different states of SiO and SiS molecules

The true potential energy curves forX1Σ+, a3πr,A1π,e3Σ−,E1Σ+,c3πi states of astrophysically important molecule SiO, whose spectra were observed in the sunspots, have been constructed using the method of Lakshman and Rao. Dissociation energy and ionization potential have been estimated as 65,350 cm−1 and 92,854 cm−1 respectively and found to be in good agreement with the values cited in literature.

Deperturbation study of the 0–1 band of the d3Π i- b3Π r transition of the SiO molecule

The structure of the (0–1) band of the d 3Π i - b 3Π r system of SiO has been photographed under high resolution with a chemiluminescent flame source, and a rotational analysis has been carried out. All theoretically predicted 27 branches of the d 3Π i - b 3Π r transition have been identified. The upper-state level is shown to be perturbed by the v = 23 level of the A 1Π state. Due to mixing of the A 1Π with the d 3Π, the (23-1) band of the A 1Π- b 3Π r transition has also been observed. The deperturbed molecular constants of the d 3Π i and A 1Π levels have been evaluated.

The chemiluminescent flame spectrum of SiO

The band systems of the SiO molecule have been excited in a flame produced by the chemiluminescence of SiCl 4 vapor reacting with oxygen atoms in the presence of an argon atmosphere. A general survey has been made of the emission spectrum of this flame and the various band systems lying in the region 2300–4600 Å have been identified. Many new bands have been observed and have been assigned to the SiO molecule. The emission bands tentatively attributed to a new 1Σ −- 1Σ − transition of neutral SiO [H. Bredohl, R. Cornet, I. Dubois, and F. Remy, Can. J. Phys. 51, 2322 (1973)] and reassigned by R. F. Barrow and T. J. Stone [ J. Phys. B. 8, L13 (1975)] to belong to the known E 1Σ +- X 1Σ + system of SiO have been extended in the present source. They are shown to confirm the Barrow and Stone assignments. A few bandheads corresponding to the isotopic species 29SiO and 30SiO have been observed for A 1Π- X 1Σ + system. In addition, several strong unidentified bands have been reported.

New wet-replication technique. II. Replication of various wet specimens

The physical ability of a differentially pumped hydration chamber to replicate water surfaces and droplets has been proven in the preceding report. This has provided a new approach to tackle some questions of solid-state nucleation, aerosol science, and fluid dynamics. In this report, the physical aspects of the wet-replication technique have been described with particular attention to the flow of evaporating gases through saturated water vapor in a hydration chamber. The reasons for selecting SiO as the replicating material when biological specimens are used are explained. At low water-vapor pressure the outward SiO beam is diffracted by the streaming water vapor. At higher vapor pressures the flow pattern changes to an effusive type and cross-beam collision predominates near the axis of the inner aperture. The penetrating central SiO beam is thus involved in random collisions until it is thermalized in the water vapor. Some SiO molecules are dragged or diffused toward the cooler specimen surface to produce a replica of all lateral and reentrant surfaces of the specimen. This shape-replication ability of the present technique has been demonstrated using objects of various sizes in the range 100 Å–10 μm and of different degrees of rigidity. The technique at hand may have some limitations when applied on delicate processes and to soft biological materials, and some modifications of the technique are suggested accordingly.

GJ-Faktor der Molekeln SiO und PbTe und Anisotropie der Magnetisierbarkeit von SiO / Molecular gJ-Factor of SiO and PbTe and Magnetic Susceptibility Anisotropy of SiO

The gJ-factor of the molecules 28Si16O and 208Pb130Te and the magnetic susceptibility anisotropy ξT of 28Si16O have been measured in the ground vibrational state: The molecular quadrupole moment and its electronic part are derived for the SiO molecule from gJ, ξT , and the rotational constant B0 .

Influence of adsorbed SiO molecules on the field electron emission of p-type germanium: R Z Bakhtizin and V I Stepanov, Fiz Tverd Tela, 14 (1), 1972, 294–296 ( in Russian)

Influence of adsorbed SiO molecules on the field electron emission of p-type germanium: R Z Bakhtizin and V I Stepanov, Fiz Tverd Tela, 14 (1), 1972, 294–296 ( in Russian)

On the E1Σ+–X1Σ+ System of SiO in the Vacuum Ultraviolet Region

The E1Σ+–X1Σ+ system attributed to the SiO molecule has been obtained in absorption in flash discharges through SiH4 containing traces of oxygen. The region from 1 650 Å to 2 000 Å has been studied. The fifteen deepest vibrational levels of the E state have been analysed. The following molecular constants have been derived:T0 = 52 578.31 cm-1ω'e = 675.52 cm-1ω'eχ'e = 4.204 cm-1B'e = 0.54727 cm-1r'e = 1.7399 ÅD'e = 1.43 × 10-6 cm-1

A 3Σ–3Π transition of the SiO molecule

The spectrum in the region 4200–4300 Å, attributed to the SiO molecule, has been excited strongly in a r.f. discharge through a mixture of argon and a trace of SiCl4 vapor flowing through a quartz tube. The spectrum consists of a single sequence Δν = 0. The 0–0 and 1–1 bands have been photographed at high dispersion. A rotational analysis of these bands shows that they involve a 3Σ–3II transition and not a 1Σ–3Π transition as reported earlier. The following rotational constants were determined:[Formula: see text]

The Spectrum of VY Canis Majoris from 2.9 to 14 Microns

view Abstract Citations (20) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Spectrum of VY Canis Majoris from 2.9 to 14 Microns Gillett, F. C. ; Stein, W. A. ; Solomon, P. M. Abstract The bright infrared object VY CMa has been observed from X = 2.9 to X = 14 with a resolution = 0.01A).02. Three independent observations show an absorption feature extending from about X 7.7 to X 9 . Preliminary analysis indicates that the band can be attributed to SiO molecules in the extended atmosphere of the star. It is difficult, however, to reconcile these results with previous models that have been suggested for the object. Publication: The Astrophysical Journal Pub Date: June 1970 DOI: 10.1086/180553 Bibcode: 1970ApJ...160L.173G full text sources ADS | data products SIMBAD (2)

A Possible Identification of Interstellar Silicate Absorption in the Infrared Spectrum of 119 Tauri

view Abstract Citations (66) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Possible Identification of Interstellar Silicate Absorption in the Infrared Spectrum of 119 Tauri Knacke, R. F. ; Gaustad, J. E. ; Gillett, F. C. ; Stein, W. A. Abstract The infrared spectrum of the reddened M supergiant 119 Tauri has been observed at low resolution from 2.9 to 12 ~ Broad absorption features at 5 and 8 jh, similar to those in other M-star spectra, are attributed to the fundamental vibration-rotation bands of CO and SiO molecules in the stellar atmos- phere. Additional features at 9.7 and 10.6 j~ may be produced by a silicate mineral, possibly (Mg,Fe)Si03, in the interstellar grains Publication: The Astrophysical Journal Pub Date: March 1969 DOI: 10.1086/180333 Bibcode: 1969ApJ...155L.189K full text sources ADS | data products SIMBAD (3)