Line Intensity of R(0) and R(3) of the CH4 2ν3 Band from Diode Laser Spectroscopy

We have determined the spectroscopic parameters that are necessary to describe accurately the R(0) line profile of the CH₄ 2ν₃ band from about 1 Torr to a few hundred Torr of pure CH₄. The intensities determined at each pressure are in overall agreement to better than 0.7%. The R(3) manifold of the same band has also been investigated. Relative positions and absolute intensities of the three transitions composing the triplet have been determined. The intensity distribution inside the triplet is in fair agreement with recent theoretical predictions.     

Measurement of the branching ratios for the decays J/ψ → ϱπ and J/ψ → γη′

Decays of the J/ψ (3.1) resonance into final states with two charged hadrons and two photons are investigated. Branching ratios for the decays J/ψ → ?π and J/ψ → γη′ are determined to be

$\text{Г(J/ψ → pφ)}\text{Г(J/ψ → all)}\text{= (1.0± 0.2) ·10}{}^{\mathrm{?2}}\text{,}\text{Г(J/ψ → γη′)}\text{ГJ/ψ → all)}\text{= (2.0± 0.7) ·}{}^{\mathrm{?3}}$

Upper limits for the same decay modes of ψ′ (3.7) are also determined.     

I–V characteristics and critical currents in superconducting/ferromagnetic bilayers

Current–voltage (I–V) characteristics and critical current density, J_c, for the onset of vortex motion were measured at different magnetic fields, H, and temperatures, T, in a superconducting (S)/ferromagnetic (F) bilayer and in a single Nb film. We choose Nb as a superconductor and a weak ferromagnetic alloy, Pd_1−xNi_x with x = 16, as F. We found that J_c was smaller for the S/F bilayer with respect to the single Nb film. The result was related to the reduced value of the superconducting order parameter in the bilayer.     

Ab initio calculation of neutral and singly charged Mgn (n?11) clusters

Under generalized gradient approximation (GGA), geometrical structure, size dependence of stability and electronic properties of neutral Mg_n, singly charged cationic Mg_n⁺ and singly charged anionic Mg_n⁻ clusters consisting of up to 11 atoms have been studied systematically by ab initio method within the norm-conserving pseudopotentials. In addition to the electronic shell effects, the “closed” geometrical structure can also enhance the stability of the clusters. The enhanced stability for the cationic cluster resulted from the removal of an antibonding electron is larger than that for the anionic cluster by promoting an extra electron to occupy a bonding orbital. The density of states (DOS) shows the increase in interaction between valence and unoccupied states leads to an increase in s-p hybridization.     

Effect of series resistance and interface states on the I-V, C-V and G/ω-V characteristics in Au/Bi-doped polyvinyl alcohol (PVA)/n-Si Schottky barrier diodes at room temperature

The forward and reverse bias current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of the Au/PVA (Bi-doped)/n-Si Schottky barrier diodes (SBDs) have been investigated at room temperature by taking the interface states (N_ss) and series resistance (R_s) effects into account. The voltage dependent profiles of resistance (R_i) were obtained from both the I-V and C/G-V measurements by using Ohm’s Law and Nicollian methods. The obtained values of R_i with agreement each other especially at sufficiently high bias voltages which correspond the value of R_s of the diode. Therefore, the energy density distribution profile of N_ss was obtained from the forward bias I-V data taking the bias dependence of the effective barrier height (BH) Φ_e and R_s into account. The high value of ideality factor (n) was attributed to high density of N_ss and interfacial polymer layer at metal/semiconductor (M/S) interface. In order to examine the frequency dependence of some of the electrical parameters such as doping donor concentration (N_D), Φ_e, R_s and N_ss values, C-V and G/ω-V measurements of the diode were performed at room temperature in the frequency range of 50 kHz-5 MHz. Experimental results confirmed that the N_ss, R_s and interfacial layer are important parameters that influence electrical characteristics of SBD.     

I–V characterization of a quantum well infrared photodetector with stepped and graded barriers

I–V characterization of an n-type quantum well infrared photodetector which consists of stepped and graded barriers has been done under dark at temperatures between 20–300 K. Different current transport mechanisms and transition between them have been observed at temperature around 47 K. Activation energies of the electrons at various bias voltages have been obtained from the temperature dependent I–V measurements. Activation energy at zero bias has been calculated by extrapolating the bias dependence of the activation energies. Ground state energies and barrier heights of the four different quantum wells have been calculated by using an iterative technique, which depends on experimentally obtained activation energy. Ground state energies also have been calculated with transfer matrix technique and compared with iteration results. Incorporating the effect of high electron density induced electron exchange interaction on ground state energies; more consistent results with theoretical transfer matrix calculations have been obtained.     

An ab Initio Study of the ÃΠ State and the ÃΠ←X?Σ Electronic Transition of MgNC

We use the RENNER program system (see, for example, P. Jensen, G. Osmann, and P. R. Bunker, in “Computational Molecular Spectroscopy” (P. Jensen and P. R. Bunker, Eds.), Wiley, Chichester, 2000, and references therein) to make a detailed calculation of the rovibronic energies in the first excited electronic state, òΠ, of the MgNC radical. This calculation is based on ab initio data (supplemented here with points for larger bending displacements from linearity) calculated at the level of MR-SDCI(+Q)/[TZ3P+f(Mg), aug-cc-pVQZ (N and C)] by T. E. Odaka, T. Taketsugu, T. Hirano, and U. Nagashima (J. Chem. Phys.115, 1349-1354 (2001)). These authors employed ab initio derived spectroscopic constants to calculate vibronic energies using perturbation expressions (J. T. Hougen and J. P. Jesson, J. Chem. Phys.38, 1524-1525 (1963)), and their results suggested that an observed vibronic band belonging to the òΠ←X?²Σ⁺ electronic transition (R. R. Wright and T. A. Miller, J. Mol. Spectrosc.194, 219-228 (1999)) should be reassigned. The present work confirms this conclusion, which is further substantiated by the rotational structures calculated in the vibronic states and by Franck-Condon theory predicting relative intensities.     

Influence of tensile damage on V–I curve and critical current of DyBCO coated conductor

The coated conductors are subjected to mechanical and electromagnetic stresses in preparation and service. When the stress is high, the coated layer is damaged, resulting in loss of superconducting property. The present work was carried out to reveal the influence of tensile damage on V–I curve, critical current and n-value of DyBa₂Cu₃O_7−δ coated conductor. The changes of the V–I curve, critical current and n-value with increasing applied tensile strain were measured experimentally. The features of the shift of the V–I curve to the lower current range and increase in its curvature, and accordingly the decrease in critical current and n-value, with increasing applied strain, were detected. For analysis of the experimental results, the model of Fang et al, which treats with the voltage generation due to the current shunting under existent crack, was applied. The experimentally observed features were described satisfactorily.     

Laser spectroscopy of VS: hyperfine and rotational structure of the CΣ-XΣ transition

The (0,0) and (0,1) bands of the C⁴Σ⁻-X⁴Σ⁻ electronic transition of VS (near 809 and 846 nm, respectively) have been recorded at high resolution by laser-induced fluorescence, following the reaction of laser-ablated vanadium atoms with CS₂ under supersonic free-jet conditions. A least squares fit to the resolved hyperfine components of the rotational lines gives the rotational constants and bond lengths as C⁴Σ⁻: , ; X⁴Σ⁻: , . The electron spin parameters for the two states show that there are some similarities between the states of VS and those of VO, but the hyperfine parameters show that the compositions of the partly filled molecular orbitals are by no means the same. The ground state Fermi contact parameter of VS, b(X⁴Σ⁻), is only 58% of that of the ground state of VO, which implies that the σ orbital of the ground σδ² electron configuration has less than 50% vanadium 4s character. Similarly, the excited state Fermi contact parameter, b(C⁴Σ⁻), is very much smaller than that of VO. No local rotational perturbations have been found in the C⁴Σ⁻ state of VS, though an internal hyperfine perturbation between the F₂ and F₃ electron components at low N confuses the hyperfine structure and induces some forbidden (ΔJ=±2) rotational branches.     

不同E/cB值下同轴绝缘子闪络特性

基于磁场闪络抑制原理,研究了由回路电流产生的同轴自磁场对径向真空固体绝缘界面沿面闪络特性的影响规律。根据同轴结构电场E和磁场B的比值与半径无关、只与电路参数相关的特点,分别设计了E/cB（c为光速）为0.041,0.05,0.056和0.062的四种同轴电极结构,开展了有磁场和无磁场两种条件下电介质的真空沿面闪络实验研究。实验结果表明,在有利于磁场闪络抑制条件的自磁场位形下,真空沿面闪络耐压水平相比无磁场情况有明显提高,且比值E/cB越小闪络电压提高幅度越大。当E/cB比值为0.041时,沿面闪络电压可提高约1.3倍;而当自磁场位形反向时,沿面闪络电压相比于无磁场情况有所降低。     

Ab initio study of the spectroscopy of the XΠ electronic ground states of CNO and NCO

The X²Π electronic ground states of NCO and CNO have been investigated by complete ab initio methods. The dependence of the Renner-Teller parameters, ? and , on the ab initio method and on the basis set have been studied. These parameters have also been compared to experimental data for NCO. The potential energy surfaces of the X²Π state have been determined by the MRCI method and the cc-pVQZ basis set for NCO and CNO. The rovibronic levels of both isomers have been calculated variationally up to approximatively 4000 cm⁻¹ for J ? 5/2 and K ? 2, with the inclusion of the geometry dependence of the spin-orbit coupling. The agreement with experimental data obtained for NCO is remarkable. A similar accuracy for the ab initio rovibronic levels of CNO is expected since no experimental data exists for this isomer.     

Experimental studies on the Kβ/Kα intensity ratio of Zn at different thickness and pressure

Kβ/Kα intensity ratios of Zn were measured at a photon excitation energy of using a high-resolution Si(Li) detector for several thickness at different pressure. Present results were compared with theoretical data and other experimental values. The results were in good agreement theoretical values based on Hartree-Fock theory.     

Photonic band structure and effect of ε and μ on the reflectivity of one-dimensional magnetic photonic crystal structure

In this paper, we study the photonic band structure and reflection properties in one-dimensional magnetic photonic crystals (MPCs). Investigation of dispersion characteristics shows that in the case of MPCs, photonic band gaps arise due to the contrast in the wave impedance, not due to the contrast in the refractive index, while contrast in the refractive index of the two layers decides the position and number of the band gaps. We also study the effect of permittivity and permeability on reflection bands, which shows that the structure that has larger values of magnetic permeability (μ) than dielectric permittivity (ε) have wider TM-reflection bands, whereas the structure for which ε is greater than μ has wider TE-reflection bands. But the gap to mid-gap frequency ratio for TM-reflection bands is larger than TE-reflection bands. Thus, magnetic permeability has greater impact on the reflectivity of MPCs than dielectric permittivity. Finally, the analysis of the omni-reflectance in MPCs has also been studied.     

Surface tension (γLV), surface energy (γSV) and crystal-melt interfacial energy (γSL) of metals

The results of temperature-dependent surface tension calculations of pure liquids aluminium (933-1200 K) and iron (1811-2500 K), in the framework of the theoretical considerations suggested by Eyring, are presented. It is observed that the surface tension decreases linearly with temperature. The calculated surface tension data are fitted as γ = 985-0.275(T − Tm) and γ = 1560-0.387(T − Tm) for Al and Fe, respectively. Moreover, the surface tension (γ_LV) at melting point, surface energy (γ_SV) and crystal-melt interfacial energy (γ_SL) are calculated for many metals. The agreement between the calculated and the reported measured values is reasonable.     

The Near-Infrared YΣ-XΠ Transition of CuSe

The near-infrared Y²Σ⁺-X²Π transition of the diatomic molecule CuSe was observed for the first time. A King-type carbon tube furnace was used to produce the gas phase of the CuSe molecules. The Fourier transform spectrometer associated with the National Solar Observatory, Kitt Peak, Arizona was used to record the molecular emission spectrum in the region 9850-12 400 cm⁻¹. A vibronic analysis and comparisons of the spin-orbit constant and the ²Σ⁺ transition energy to those for related isovalent molecules are presented.     

Axis-Switching and Coriolis Coupling in the Ã(010)-X?(000) Transitions of DCCl and HCCl

The rotationally resolved Ã(010)-X?(000) spectrum of DCCl between 12 880 and 12 964 cm⁻¹ was measured using frequency-modulated laser absorption spectroscopy of jet-cooled and ambient temperature samples. Transitions to levels with K_a′=0 and 1 were assigned, and their analysis leads to improved accuracy of both the ground state rotational constants of DCCl and, when combined with existing data for HCCl, the geometry of the radical. In addition to the expected perpendicular band structure, a number of parallel (Δ K_a=0) subbands were observed. Their intensity derives from a combination of c-type Coriolis coupling and axis-switching (J. T. Hougen and J. K. G. Watson, 1965, Can. J. Phys.43, 298) resulting from the change in geometry between the two states. The two contributions have been calculated for the (010)-(000) band of DCCl and previously recorded data for HCCl. Satisfactory agreement with experimental measurements was obtained. The Coriolis contributions are small for these transitions, but may add to or subtract from the axis-switching. For higher bending excitation in the upper state, Coriolis coupling is predicted to make larger contributions to the parallel subband intensities.