Experimentally determined oscillator strengths and linewidths for the Schumann-Runge band system of molecular oxygen—III. The (7-0) to (19-0) bands

Experimental oscillator strengths and predissociation linewidths have been derived from equivalent width measurements at room temperature for the (11-0) to (15-0) Schumann-Runge bands of molecular oxygen, and at low temperature for the (15-0) to (19-0) bands, using the Adelaide 6 m vacuum ultraviolet monochromator operated at a resolution of 0.006 nm. Photometric methods were used to measure the ultraviolet absorption for 40 groups of ratational lines, and the resulting data were interpreted using a curve of growth type of analysis to give oscillator strengths and pre-dissociation linewidths. The variation of the oscillator strengths with N? within each band was found to agree well with the theoretical predictions of Allison, while the mean band oscillator strengths derived from the results are in good agreement with previous measurements. The results demonstrate the need for accurate data about multiplet line splittings. A revised analysis of previous data for the (7-0) to (14-0) bands is also presented.     

Experimentally determined oscillator strengths and linewidths for the Schumann-Runge band system of molecular oxygen—II. The (2-0) to (5-0) bands

Experimental oscillator strengths and predissociation linewidths have been measured at room temperature for the (2-0) to (5-0) Schumann-Runge bands of molecular oxygen using the Adelaide 6 m vacuum ultraviolet monochromator operated at a resolution of about 0.06 Å. Photoelectric detectors were used to measure the ultraviolet absorption at normally two different gas pressures for 37 groups of rotational lines, and the resulting data were interpreted using an equivalent width type of analysis. The variation with N″ of the oscillator strengths within each band was found to be smaller than that measured earlier for the higher vibrational bands. Measured oscillator strengths agree well with previously accepted values except for the (3-0) band, while the linewidths of the present work agree well with recent theoretical values for the (3-0) and (4-0) bands but are larger for the (2-0) and (5-0) bands. A modification was performed on the parameters of a recent theoretical predissociation model to produce excellent overall agreement between experimental and theoretical linewidths from ν' = 2 to 14. The present work provides results which can be used to construct accurate synthetic absorption profiles for studies of the atmospheric absorption of ultraviolet radiation by the Schumann-Runge bands.     

Experimentally determined oscillator strengths and linewidths for the Schumann-Runge band system of molecular oxygen—I. The (6-0)–(14-0) bands

Experimental oscillator strengths and predissociated linewidths have been measured at room temperature for the (6-0)–(14-0) Schumann-Runge bands of molecular oxygen using the Adelaide 6 m vacuum u.v. monochromator operated at a resolution of about 0.06 Å. Photoelectric detectors were used to measure the u.v. absorption at two different gas pressures for 138 groups of rotational lines distributed throughout the (6-0)–(14-0) bands and the resulting data were interpreted using an equivalent width type of analysis. Experimental measurements of the variation with N″ of the oscillator strengths within each band have been obtained for the first time. Measured oscillator strengths are found to be somwhat higher in general than previously reported values with a slightly faster decrease as N″ increases than is predicted theoretically. The mean predissociated linewidths obtained for each band show a smooth variation with v′, agreeing well with other results for v′=12?14 and lying between previously reported experimental and theoretical values for v′=6?9. The present work provides results which can be used to construct highly accurate synthetic absorption profiles for studies of the atmospheric absorption of u.v. radiation by the Schumann-Runge bands.     

Quantitative laser photoacoustic detector spectroscopy: HD 5-0 transitions

Intracavity photoacoustic spectroscopy of HD in the 5-0 R(0), R(1), and R(2) transitions demonstrates the use of a transition of known strength to calibrate the response of a photoacoustic detector by simultaneous in situ measurements. Excellent agreement in line strengths for the HD 5-0 transitions is found with the earlier determination due to McKellar et al. Our experiments, however, were conducted with a pressure-pathlength product only 10^-6 of that used by McKellar et al.     

Line strengths of CO2: 4550-7000 cm

Line positions and strengths of ¹²C¹⁶O₂ were measured between 4550 and 7000 cm⁻¹ using near infrared absorption spectra recorded at 0.01-0.013 cm⁻¹ resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory at Kitt Peak, Arizona. These were retrieved from 42 laboratory spectra obtained at room temperature with five absorption cells having various optical path lengths (from 0.1 to 409 m) filled with natural and enriched samples of CO₂ at pressures ranging from 2 to 581 Torr. In all, band strengths and Herman-Wallis-like F-factor coefficients were determined for 58 vibration-rotation bands from the least-squares fits of over 2100 unblended line strengths; strengths of 34 of these bands had not been previously reported. Band strengths in natural abundance generally ranged from 3.30 × 10⁻²⁰ to 2.8 × 10⁻²⁵ cm⁻¹/molecule cm⁻² at 296 K. It was found that the high J transitions (J′ ? 61) of the 20012 ← 00001 band centered at 4977.8347 cm⁻¹ are perturbed, affecting both measured positions and strengths. Two other interacting bands, 21113e ← 01101e and 40002e ← 01101e, were also analyzed using degenerate perturbation theory. Comparisons with corresponding values from the literature indicate that absolute accuracies better than 1% and precisions of 0.5% were achieved for the strongest bands.     

Intensity of CO2 bands in the 4.8- to 5.3-μm region. The (1110,0310)II-0000 band

Measurements of the line strengths of the (11¹0,03¹0)_II-00⁰0 band of CO₂ (1932.466 cm^?1) have been made with high resolution. They exhibit a strong Coriolis interaction which enhances the P-branch intensity while reducing that of the R branch. The rotationless dipole moment of the transition and the ξ-constant representing this interaction have been determined as: R(0) = (6.57 ± 0.03) × 10^?4D, ξ = ?0.0598 ± 0.0002.     

Infra-red absorption bands 1-0, 2-0, 3-0 and 4-0 of the two isotopic species D79Br and D81Br of deuterium bromide

High resolution spectra of the 1-0, 2-0, 3-0, and 4-0 infra-red absorption bands of the two isotopic species of deuterium bromide have been recorded up to very high J values. The equilibrium molecular parameters obtained in the analysis fit the 267 observed lines within their experimental uncertainties, and give precise calculated wavenumbers for some observed chemical laser lines of these molecules.     

Mixing and CP violation: fromB^0 - \overline {B^0 } to T^0 - \overline {T^0 }

We extend from \(B^0 - \overline {B^0 } to T^0 - \overline {T^0 } \) the study of neutral pseudoscalar mesons with respect to mixing and CP violation. The possibility of a quite large top quark mass necessitates a more careful computation of the box diagram amplitude. Our result is that, while in \(B^0 - \overline {B^0 } \) systems CP violation is expected to be very small (～10^?6) and mixing quite large (10–20% or more), precisely the opposite occurs for \( T^0 - \overline {T^0 } \) . In particular, CP violation in the \( T_u^0 - \overline {T_u^0 } \) system could be of the same order of magnitude as in the \(K^0 - \overline {K^0 } \) system (～10^?3) while the mixing is totally negligible.     

Empirical low energy values for methane transitions in the 5852-6181 cm region by absorption spectroscopy at 81 K

The high resolution absorption spectrum of methane has been recorded at liquid nitrogen temperature by direct absorption spectroscopy between 1.62 and 1.71 μm (5852-6181 cm⁻¹) using a newly developed cryogenic cell and a series of distributed feedback (DFB) laser diodes. The minimum value of the measured line intensities is on the order of 3 × 10⁻²⁶ cm/molecule The investigated spectral range corresponds to the high energy part of the tetradecad dominated by the 2ν₃ band for which a theoretical treatment is not yet available. The positions and strengths at 81 K of 2187 transitions were obtained from the spectrum analysis. From the values of the line strength at liquid nitrogen and room temperatures, the low energy values of 845 transitions could be determined. The obtained results are discussed in relation with the previous work of Margolis and compared to the line list provided by the HITRAN database.     

Rotation-vibration spectrum of HT: Line position measurements of the 1-0, 4-0, and 5-0 bands

Optoacoustic techniques have been used to determine the line positions of the 1-0 fundamental and 4-0 and 5-0 overtones of the HT (¹H³H) molecule with an accuracy of better than 0.01 cm⁻¹. Comparison with line positions predicted from ab initio calculations that include adiabatic, relativistic, radiative, and nonadiabatic corrections shows disagreement outside of the experimental uncertainties.     

Predissociation linewidths and oscillator strengths for the (2-0) to (13-0) Schumann-Runge bands of O2

Analysis of the absorption spectrum of O₂ in the Schumann-Runge bands (B³Σ_u^?-X³Σ_g^?) from the 2-0 to the 13-0 band yields oscillator strengths which are in good agreement with past theoretical calculations. Predissociation linewidths deduced from the data tend to be larger than theoretical predictions for v′ ≤ 5 and are reasonably near theory for v′ > 5. The qualitative dependence of the linewidths on vibrational level is in accord with that expected for a repulsive potential intersecting the B³Σ state near v′ = 4. For a given band the predissociation linewidth deduced from the spectra tends to increase as the total angular momentum increases. The new linewidths are smaller than some past experimental results, and this will have an impact on future calculations of the photodissociation rates of O₂, NO, and H₂O in the earth's upper atmosphere.     

Rotational Analysis of the 0-0 and 1-0 B-X Bands of Ga18O Molecules

The B²Σ⁺-X^{2 +} system of the ⁶⁹Ga¹⁸O and ⁷¹Ga¹⁸O molecules excited in a low-pressure arc, has been recorded in the region between 300 and 500 nm. The 0-0 and 1-0 bands of both molecular species have been rotationally analyzed and the molecular constants of involved states have been derived.     

Density functional study of ethylamine and allylamine on Si(1 0 0)-2 × 1 and Ge(1 0 0)-2 × 1 surfaces

We have investigated the interactions of ethylamine and allylamine with models of the Si(1 0 0)-2 × 1 and Ge(1 0 0)-2 × 1 semiconductor surfaces. Ab initio molecular orbital calculations, along with density functional theory (DFT), are used to examine the interaction of these amines with cluster models of the semiconductor surfaces. The transition states and final adsorption products for adsorption of the molecules are predicted. The DFT calculations show the amines form N-dative bond states with Si(1 0 0)-2 × 1 or Ge(1 0 0)-2 × 1 as the initial adsorption product. The initial dative-bond products can be further activated, resulting in N-H bond cleavage on both surfaces. The overall reaction of a given amine on Si(1 0 0) via N-H dissociation is more exothermic than on the Ge(1 0 0) surface.     

Absolute frequency measurements of the 0002-0000, 2001-0000, and 1201-0000 bands of N2O by heterodyne spectroscopy

The absolute frequencies of 39 lines in the 00⁰2-00⁰0, 20⁰1-00⁰0, and 12⁰1-00⁰0 bands of N₂O in the range 4300–4800 cm^?1 have been measured by heterodyne frequency techniques. The lines were each measured in Doppler-limited absorption, with a color-center laser as a tunable probe of the N₂O and two stabilized CO₂ lasers as reference frequencies. New rovibrational constants have been fitted to these measurements. Tables of calculated transition frequencies are given, with estimated absolute uncertainties as small as 10^?4 cm^?1. The pressure shifts of four lines have been measured, and the values fall within the range of 0 to ?2 MHz/kPa (0 to ?0.2 MHz/Torr).     

First-principles study of adsorption and diffusion on Ge/Si(0 0 1)-(2 × 8) and Ge/Si(1 0 5)-(1 × 2) surfaces

Using first-principles total-energy calculations, we have investigated the adsorption and diffusion of Si and Ge adatoms on Ge/Si(0 0 1)-(2 × 8) and Ge/Si(1 0 5)-(1 × 2) surfaces. The dimer vacancy lines on Ge/Si(0 0 1)-(2 × 8) and the alternate S_A and rebonded S_B steps on Ge/Si(1 0 5)-(1 × 2) are found to strongly influence the adatom kinetics. On Ge/Si(0 0 1)-(2 × 8) surface, the fast diffusion path is found to be along the dimer vacancy line (DVL), reversing the diffusion anisotropy on Si(0 0 1). Also, there exists a repulsion between the adatom and the DVL, which is expected to increase the adatom density and hence island nucleation rate in between the DVLs. On Ge/Si(1 0 5)-(1 × 2) surface, the overall diffusion barrier of Si(Ge) along direction is relative fast with a barrier of ∼0.83(0.61) eV, despite of the large surface undulation. This indicates that the adatoms can rapidly diffuse up and down the (1 0 5)-faceted Ge hut island. The diffusion is also almost isotropic along [0 1 0] and directions.     

B0-B(-)0 mixing beyond factorization in QCD sum rules

We present a calculation of the B0-B(-)0 mixing matrix element in the framework of QCD sum rules for three-point functions. We compute alpha(s) corrections to a three-point function at the three-loop level in QCD perturbation theory, which allows one to extract the matrix element with next-to-leading order (NLO) accuracy. This calculation is imperative for a consistent evaluation of experimentally measured mixing parameters since the coefficient functions of the effective Hamiltonian for B0-B(-)0 mixing are known at NLO. We find that radiative corrections violate factorization at NLO; this violation is under full control and amounts to 10%. The resulting value of the B parameter is found to be B(B)(m(b))=1+0.1(PT)-0.05(non-PT).     

Chemisorption of 4-(4-amino-phenylazo) benzoic acid molecule on the Si(0 0 1)-(4 × 2) surface

Structural and electronic properties of self-assembled monolayer with 4-(4-amino-phenylazo) benzoic acid (APABA) on the Si(0 0 1)-(4 × 2) surface are investigated by ab initio calculation based on density functional theory. For the APABA chemisorption on the silicon surface, we have assumed two different binding sites: (i) amino group of molecule and (ii) carboxyl group of molecule. Considering amino-site, we have assumed two possible models for the chemisorption of molecules on the Si(0 0 1)-(4 × 2) surface: (i) an intrarow position between two neighboring Si dimers in the same dimer row (Model I), (ii) on-dimer position (Model II). We have found that Model II is 1.10 eV energetically more favorable than Model I. The Si-N bond length was calculated as 1.85 Å which is in excellent agreement with the sum of the corresponding covalent radii of 1.87 Å. Considering carboxyl-site, we have assumed exactly the same model as mentioned above. Again we have found that Model II is energetically favorable than Model I. The calculated bond lengths for Si-O and O-C are 1.76 and 1.35 Å, respectively.     

ThTiO_4~(-/0),Th_2TiO_6~(-/0)和ThTi_2O_6~(-/0)的电子结构和化学成键的密度泛函理论研究

本文采用B3LYP密度泛函理论方法,探究双核、三核掺杂钍氧簇体系ThTiO_4~(-/0)、Th_2TiO_6~(-/0)和ThTi_2O_6~(-/0)的几何构型、电子结构和化学成键等规律,并与等价电子体(TiO_2)-/0n(n=2,3)进行对比,研究掺杂效应对于掺杂体系的结构和成键等性质的影响.结果表明:掺杂钍氧簇与其等价电子体(TiO_2)-/0n(n=2,3)具有类似的键连方式.ThTiO_4~-中单电子占据的位置与Ti2O-4中单电子的所处位置类似,都是被两个金属原子共用,而Th_2 TiO_6~-,Th Ti_2O_6~-以及Ti_3O_6~-中的单电子均处于那个不含端氧的金属原子上.     

Soft X-ray appearance potential spectroscopy (SXAPS) study of TiO2(1 1 0)-1 × 2 and (0 0 1)-1 × 1 surfaces

A soft X-ray appearance potential spectroscopy (SXAPS) apparatus with high sensitivity was built to measure non-derivative spectra. SXAPS spectra (non-derivative) of Ti 2p and O 1s for TiO₂(1 1 0)-1 × 2 and (0 0 1)-1 × 1 surfaces have been measured using low incident currents (about 10 μA/cm²) and a photon counting mode. Density of empty states on Ti and O sites are deduced by self-deconvoluting the spectra. The self-deconvoluted SXAPS spectra are qualitatively similar to those measured by X-ray absorption spectroscopy (XAS). The Ti 2p_3/2 spectrum shows two strong peaks which correspond to t_2g and e_g states. For the O 1s spectrum two strong peaks near the threshold are also found which can be ascribed to O 2pπ and O 2pσ states. These results suggest that the spectra almost obey the dipole selection rule, so-called the “approximate dipole selection rule”. The SXAPS spectra of Ti 2p and O 1s for the (1 1 0) and (0 0 1) surfaces resemble qualitatively, which is consistent with the XAS results. The spectra measured on the (1 1 0)-1 × 2 surface at an incident angle of 45° off normal to the surface and on the (1 1 0) surface sputtered by Ar ions indicate that SXAPS is very sensitive to the surface electronic states.     

CP Asymmetries in Two-Body Baryonic Decays of Bd0 - Bd0 System

The partialdecay-rate asymmetries indicating the CP violating effects in two-body baryonic decays of B: - B: eystem are systematically studied. It turns out that the CP asymmetries are large in some processes, 1.6×l0⁸, 5.5×l0⁹ and 4.2 x 10⁹ bb pairs are needed for testing the CP violation in B_d⁰ - B_d⁰ → pp, Δ⁰Δ ⁰ and Δ⁺⁺Δ ⁺⁺, respectively. It is impossible to detect the CP violating effects in those decays where penguin diagrams dominate.