States Of SiO Research Articles

Self-trapped excitons and interstitial-vacancy pairs in oxides

Abstract Experimental data on the temperature dependence of the lifetimes of transient luminescence, optical absorption, and volume change, associated with self-trapped excitons (STEs), as well as the observed optical conversion from defect pairs (DPs) to STEs, have inspired two recent theoretical studies aimed at STEs and DPs in SiO2. One is a quantum-mechanical reaction-rate processing of the lifetime versus temperature data, while the other is a quantum-chemical study of excitons and DPs, both aiming at revealing the character of the STE and DP structures, as well as of the adiabatic potential energy surfaces (APESs) and ionic displacements resulting in the STE-to-DP interconversion. Both theoretical approaches are found to lead to convergent conclusions which are now summarized and discussed from a unified viewpoint. It is shown that qualitative characteristics of the APES of the lowest excited state of SiO, can also be related to a wider class of compounds with highly ionic and mixed ionic-covalent b...

AN APPROACH TO VISIBLE CHEMICAL LASER DEVELOPMENT USING FAST NEAR RESONANT ENERGY TRANSFER

Abstract - Extremely efficient near resonant intermolecular energy transfer from selectively formed metastable states of SiO and GeO is used to pump select receptor atoms with a focus on the creation of visible chemical laser amplifiers and oscillators. Visible transitions associated with thallium (A = 535nm), gallium (A = 417nm), sodium (A = 569,616,319nm), and potassium receptor atoms have been considered. A detailed outline of the alkali based systems is presented. 1. Introduction Certain unique aspects of a very select group of high quantum yield, highly exother- mic simple metal or metalloid oxidations show the promise of creating an energy storage medium which can be used to develop what appear to be the first chemically driven laser amplifiers (and oscillators) operating in the visible spectral region.l Created population inversions rely on ultrafast near resonant intermolecular energy transfer from metastable oxide storage states formed in chemical reaction to pump subsequently amplifying receptor atom transitions including those associated with thallium

Reduction of the concentration of slow insulator states in SiO 2/InP-MIS structures

The well-known drift phenomena usually found in the InP-metal-insulator-semiconductor (MIS) devices can be explained by the assumption of a spatial and energetical distribution of slow states located within the insulator. The concentration of these states can be reduced by far more than one order of magnitude if a suitable technique of insulator deposition is applied. In this paper we will discuss the influence of the deposition temperature, the spatial separation of sample and plasma (“indirect plasma method”), and the addition of phosphorus into the reaction chamber during the initial period of insulator deposition on the properties of n-type and p-type InP-MIS capacitors. Plasma-enhanced chemical vapor deposited silicon dioxide is used as insulator. The samples were characterized by means of capacitance/voltage ( C( V)) and deep level transient spectroscopy (DLTS) measurements. Only minor hysteresis of the C( V) curves and concentrations of slow insulator states of only (1–2)×10 11 cm -2 eV -1 are measured for the best of our samples.

Diffusion of radiolytic molecular hydrogen as a mechanism for the post-irradiation buildup of interface states in SiO2-on-Si structures

A review is made of recent literature dealing with radiation-induced point defects distributed volumetrically in thermally grown SiO2-on-Si or superficially at the silicon interface, with particular emphasis on the results of electron-spin-resonance experimentation. The observed defect types and their anneal kinetics are then compared with recent advances in the understanding of similar species and processes in irradiated bulk fused silica. It is concluded that radiolytic molecular hydrogen is formed in thermally grown SiO2 layers, just as it is in bulk fused silica, and that the diffusion of this hydrogen determines the temperature and time dependencies of the post-irradiation interface state buildups.

Ab initio calculations of radiative transition probabilities in the X 1σ + state of SiO and the X 2σ +and A 2 Π states of SiO +

Potential energy and dipole moment functions have been calculated for the X 1σ + state of SiO and for the X 2σ + and A 2 Π states of SiO + using MC SCF wavefunctions and large basis sets. For SiO the calculated dipole moment of 3.01 D is in good agreement wth the experimental value of 3.088 D. The dipole moments of the X and A states of SiO + are calculated to be 4.28 D and 2.89 D. respectively. For SiO + the transition moment function between the X and A states has also been evaluated, and rates for all important transitions within and between the X and A states are given (υ ⩽ 10): The SiO + ion is predicted to be an excellent IR emitter. It is found that all vibrational levels between 1 ⩽ υ ⩽ 10 of the X 2σ + state are almost entirely radiatively depopulated via transitions into energetically lower-lying vibrational levels of the A 2Π state. From the transition rates radiative lifetimes for the first ten vibrational levels of each state have be predicted. For the X state they lie between 70 μs and 423 ms and for the A state between 140 μs and 336 ms.

Masing and nonmasing silicon monoxide emission from evolved stars

view Abstract Citations (18) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Masing and nonmasing silicon monoxide emission from evolved stars. Wolff, R. S. ; Carlson, E. R. Abstract Observations of the J = 3-2 and J = 2-1 rotational transitions in the ground (nu = 0) and first vibrational (nu = 1) states of SiO toward six evolved stars are reported. Comparisons of the line widths of the two ground state rotational transitions indicate that the thermal emission regions are not coextensive in all stars, with the J = 3-2 line exhibiting a greater velocity dispersion. The J = (3-2)/(2-1) (nu = 0) line intensity ratio is also found to vary from star to star, and there is a general tendency of both line width and integrated intensity to increase with infrared color excess. The masing (nu = 1) J = 3-2 and J = 2-1 transitions show marked variability in both line shape and intensity. Repeated observations of the J = 2-1 (nu = 1) transition indicate that the integrated line intensities vary in phase with the IR fluxes of the periodically variable stars. A search for emission in the J = 2-1 line of the (nu = 2) excited state yielded negative results in all cases. Publication: The Astrophysical Journal Pub Date: June 1982 DOI: 10.1086/159974 Bibcode: 1982ApJ...257..161W Keywords: Emission Spectra; Late Stars; Masers; Silicon Oxides; Stellar Envelopes; Stellar Evolution; Infrared Spectra; Spectral Energy Distribution; Spectral Line Width; Stellar Spectrophotometry; Variable Stars; Vibrational Spectra; Astrophysics full text sources ADS | data products SIMBAD (6)

Chemiluminescent SiCl4 + O2 + Ar/He/ Reactions

Abstract A chemiluminescent flame was formed in the reaction between SiCl4 and oxygen in an atmosphere of argon or helium. Internal state distributions of some reaction products were studied. Inverted vibrational populations in the A1φ and f3φi states of SiO were observed. The relative electronic populations of atomic silicon and relative rotational populations in the SiO A1φ state corresponded to temperatures of about 3400 K and 400 K, respectively.

Rydberg series in the vacuum ultraviolet absorption spectrum of silicon monoxide

New observations of the absorption spectrum of SiO in the 700-1500 AA wavelength range are reported. The experiments were performed with a 1 m normal incidence spectrograph at the synchrotron radiation facility of the 500 MeV accelerator in Bonn. The known band systems have been extended, and a Rydberg series converging on the x2 Sigma + state of SiO+ has been found from which an improved value of the ionisation potential is derived (11.584+or-011 eV). A further Rydberg series above the first ionisation threshold is found to converge on the B2 Sigma + state of SiO+ at 14.805 eV.

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.

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.

Interface States Induced by Amorphous SiO2 in MOS Structures

In order to understand physical origin of interface states in MOS structures, model calculations of the interface states are carried out. The model of the ideal Si–SiO 2 , interface is introduced. This model represents that the Si–SiO 2 interface is given as the boundary between two bonding-type materials and the intrinsic interface state is absent. It will be assumed that observed interface state is caused by the difference between real interface and the ideal one. The real boundary of MOS structures may be described approximately in terms of the crystalline Si and the amorphous SiO 2 with an ideal glassy structure. Based on the simple model of amorphous SiO 2 , the density of interface states is calculated semi-qualitatively. The obtained results suggest that the interface states induced by the amorphous SiO 2 do not give the observed density of the interface states and the amorphous state of SiO may take into account this density.

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.

Spectroscopic constants and radiative lifetimes for valence-excited bound states in SiO

Using the self-consistent polarization propagator approximation we have calculated the spectroscopic constants for the following bound states in silicon monoxide: a 3Σ+, b3Π, d3Δ, e 3Σ-, C 1Σ+, D 1Δ, A 1Π, E 1Σ+, 3Σ+(II), 3Σ+(III), 3Π (III), F 1Σ+, H 1Σ+, and G 1Π. The molecular parameters for the seven lowest states agree very well with experiments, whereas the seven remaining levels were determined less accurately. The electronic transition moments were calculated for the dipole allowed transitions. The calculated radiative lifetime for the A 1Π state was found to be 49.5 nsec. With the experimental potential energy curves the corresponding lifetime was 31.6 nsec.

Perturbations in the A1Π state of SiO

Perturbations in the nu =0 level of the A1 Pi state of SiO have been observed through the appearance of strong extra lines by applying fast-pumping techniques.

The spectrum of SiO in the vacuum ultraviolet region

The absorption spectrum of SiO has been photographed at high resolution in the region 1200–1500 Å. Several new electronic states have been observed, valence states as well as Rydberg states. Tables of the molecular constants of all the known states of SiO are given. Due to interactions between the electronic states, the constants of all states analyzed vary irregularly. From the Rydberg series a value of the ionization potential has been derived. It agrees with the value earlier reported, 11.6 ± 0.2 eV.