Fourier transform spectral study of BΣ-XΣ system of AlO

The spectrum of B²Σ⁺-X²Σ⁺ system of AlO has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of 0.05 cm⁻¹. Nineteen bands of the Δv = 1, 0, −1, and −2 sequences of this band system have been analyzed for the rotational structure. Out of which seven bands, viz. 3-2, 4-3, 2-3, 3-4, 4-5, 5-6 and 6-7 have been analyzed for the first time. The rotational lines of these 19 bands along with 20 earlier analyzed bands, a total of 7200 lines, have been fitted in a simultaneous least squares fit. The study has resulted in determining more precise vibrational and rotational constants of the two states. Because of the high resolution employed it became necessary to invoke H₀ and H₁ coefficients, and a fifth order term to explain the anomalous spin-doubling observed in the v″ = 5, 6 and 7 levels of the X²Σ⁺ state.     

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.     

Fourier Transform Emission Spectroscopy of the FΣ-XΣ System of RuN

Emission spectra of RuN have been recorded at high resolution in the region 12 000-35 000 cm⁻¹ using a Fourier transform spectrometer. The molecules were excited in a ruthenium hollow cathode lamp in the presence of about 2.5 Torr of Ne and 5 m Torr of N₂. New bands with origins near 17 758.1, 18 866.4, 19 800.4 and 20 721.5 cm⁻¹ have been assigned as the 0-1, 0-0, 1-0, and 2-0 bands of a new ²Σ⁺-²Σ⁺ system with the lower state as the ground state. This transition has been labeled as F²Σ⁺-X²Σ⁺, with the F²Σ⁺ state arising from the 1σ²2σ²1π⁴1δ⁴4σ¹ configuration. A rotational analysis of these bands has been carried out and spectroscopic constants have been extracted. The principal equilibrium constants for the ground state of RuN are ΔG(1/2)″=1108.3235(22) cm⁻¹, B_e″=0.5545023(42) cm⁻¹, α_e″=0.0034468(57) cm⁻¹, r_e″=1.5714269(60) Å, while the equilibrium constants for the excited state are ω_e′=946.8471(40) cm⁻¹, ω_ex_e′=6.4229(14) cm⁻¹, B_e′=0.50085(21) cm⁻¹, α_e′=0.00375(10) cm⁻¹, r_e′=1.65345(34) Å. This transition is analogous to the E²Σ⁺-X²Σ⁺ system of RhC (W. J. Balfour et al., J. Mol. Spectrosc.198, 393 (1999)).     

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.     

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.     

High-resolution Fourier transform emission spectroscopy of the AΠ-XΣ system of GeSe

Natural germanium and selenium consist of, respectively, five and six stable isotopes. Several of these isotopes have considerable abundances and one should expect to observe the bands of at least six isotopic variants of germanium monoselenide (GeSe). In this paper, for the first time, the results of the high-resolution electronic spectrum of the main transition A¹Π-X¹Σ⁺ of the specific isotopomer ⁷⁴Ge⁸⁰Se, excited in a microwave discharge and recorded in the 33 500-26 000 cm⁻¹ region using a Fourier transform spectrometer, is discussed. From the rotational analysis of 25 bands involving v″ = 0-12 and v′ = 0-7, accurate vibrational and rotational constants of the A¹Π state are determined. The present study has revealed perturbations in the v′ = 6 and 7 levels of the A¹Π state.     

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.     

The Fourier Transform Emission Spectrum of BΠ1-XΣ Band-System of InCl

The emission spectrum of the B³Π₁-X¹Σ⁺ band-system of the InCl molecule has been recorded on a Fourier transform spectrometer at an apodized resolution of 0.025 cm⁻¹. The rotational structure of 1-0, 2-1, 0-0, 0-1, 1-2, 0-2, and 1-3 bands belonging to the B³Π₁-X¹Σ⁺ transition of In³⁵Cl has been analyzed and accurate equilibrium rotational constants of the B³Π₁ state, have been obtained. Precise Λ-doubling constants of the B³Π₁ state (v=0, 1, and 2) are also reported for the first time.     

Rotationally Resolved LIF Spectra of the AΣ-XΠr Transition of Jet-Cooled GeCl

The A²Σ⁺-X²Π_r band system of ⁷⁴Ge³⁵Cl has been rotationally resolved for the first time using isotopically enriched ⁷⁴GeCl₄ as the precursor in a pulsed discharge jet experiment. The previous vibrational analysis of W. J. Balfour and K. S. Chandrasekhar (1986, J. Phys. B19, L187-L191) has been verified from the observed isotopic splittings of both the chlorine and germanium isotopomers. The ²Π_1/2 components of three vibronic bands have been rotationally analyzed leading to revised values for the ground state rotational constant B″₀=0.154165(35) cm⁻¹ and the lambda-doubling constant p″₀=6.560(97)×10⁻³ cm⁻¹. We have experimentally determined the value of B′_e=0.118710(24) cm⁻¹ for the A²Σ⁺ state leading to an excited state equilibrium bond length of 2.44581(25) Å.     

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.     

Calculation of on-state I–V characteristics of LDMOSFETs based on an accurate LDD resistance modeling

In this paper, we present an I–V model for LDMOSFETs. It is based on modeling the Lightly-Doped Drain (LDD) region of the device as voltage-controlled resistors where velocity saturation effect is also taken into account. Using the LDD region model along with a model for the channel region of the device, the on-state I–V characteristic of the transistor is accurately calculated. The models for the LDD region resistors can be incorporated into a circuit simulator such as HSPICE which has an accurate model for the channel region of the transistor. The accuracy of the models is verified by comparing its results with those of a device simulator. The results show a maximum error of 1% for a wide range of voltages and overlapped LDD region lengths.     

Anomalous B–H behaviour of electrical steels at very low flux density

The behaviour of ferromagnetic materials under very low magnetic field was investigated more than a century ago by Lord Rayleigh. However, it has been shown since that the so-called Rayleigh law fails for very low magnetic fields, although the explanation for this phenomenon was not given. An anomalous B–H behaviour at very low alternating peak flux density in conventional grain-oriented (GO) and non-oriented (NO) electrical steels is reported. It has been found that the initial permeability is constant for all the measured frequencies (from 20 to 400 Hz) at peak flux density below 0.1 mT, and in this region the magnetisation is almost reversible (for both GO and NO). At higher flux density the B–H loops become visibly irreversible, with a relatively narrow (for GO) or very wide (for NO) transition region. For GO the B–H loop becomes visibly “distorted” for all frequencies at around 2 mT. The eddy current loss calculated from the so-called “classical” equation gives values higher than the measured total losses at lower frequencies. Both these measured results are difficult to explain.     

A Theoretical Study of AtildeΠ MgCN

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 MgCN radical. This calculation is based on ab initio data computed at the MR-SDCI(+Q)/[TZ3P+f (Mg), aug-cc-pVQZ (N and C)] level of theory. We have also obtained the standard spectroscopic constants and have used these to calculate vibronic energies from perturbation expressions (J. T. Hougen and J. P. Jesson, J. Chem. Phys.38, 1524-1525 (1963)); these results are compared to those computed with RENNER. It is shown that for MgCN, the perturbation theory is dilapidated due to Fermi resonances. No spectra involving the Ã²Π electronic state of MgCN have been observed. To assist such observations, we have calculated Franck-Condon factors for some of the vibronic bands in the òΠ←Xtilde;²Σ⁺ electronic transition.     

Intracavity laser absorption spectroscopy of AuO: Identification of the BΣ-XΠ3/2 transition

The visible electronic spectrum of AuO has been recorded at rotational resolution using intracavity laser absorption spectroscopy. Six vibrational bandheads have been identified, and three of the bands have been analyzed and assigned as bands of a newly identified B²Σ⁻-X²Π_3/2 transition of AuO. The molecular parameters for the newly identified B²Σ⁻ state are presented.     

High-Resolution Fourier Transform Study of MgCl: The AΠ-XΣ Band System

The A²Π-X²Σ⁺ emission band system of the MgCl molecule has been studied by means of high-resolution Fourier transform spectroscopy. Excited MgCl molecules were produced by two different techniques: (i) at Orsay, they were created by mixing Mg vapor with a flow of He/Cl₂ and excited in a “heated” Schüller-type discharge tube, and (ii) at Waterloo, they were generated by using a copper hollow cathode lamp loaded with MgCl₂ powder. Rovibronic analysis of the (0, 0) and (0, 1) bands was performed. Molecular constants were derived in a weighted nonlinear least squares fit, including both the new line positions and the previously published microwave frequencies (M. Bogey, C. Demuynck, and J. L. Destombes, Chem. Phys. Lett.155, 265 (1989); Y. Ohshima and Y. Endo, Chem. Phys. Lett.213, 95 (1993)).     

Sub-millimeter spectroscopy of BaS (XΣ)

The pure rotational spectrum of BaS (X¹Σ⁺) has been recorded in the frequency range 355-396 GHz using direct absorption methods. Data were recorded for six isotopomers: ¹³⁸Ba³²S, ¹³⁷Ba³²S, ¹³⁶B³²S, ¹³⁵Ba³²S, ¹³⁴Ba³²S, and ¹³⁸Ba³⁴S, in vibrational states ranging from v = 0 to v = 6. This work is an extension of past microwave and millimeter studies. Revised spectroscopic constants have been established for the six species. The dissociation energy for ¹³⁸Ba³²S is estimated to be 42 392 cm⁻¹.     

Magnetic properties of CoPt–SiNx/Ag nanocomposite films

When the thickness of Ag under layer is 25 nm, the CoPt/Ag film has maximum out-of-plane squareness (S_⊥), minimum in-plane squareness (S_∥), and the largest out-of-plane coercivity (H_c⊥), they are 0.95, 0.35, and 15 kOe, respectively. Different volume percent of SiN_x ceramic materials were co-sputtered with Co₅₀Pt₅₀ films on the Ag under layer to reduce the grain size of the CoPt film. Comparing the X-ray diffraction pattern of CoPt-SiN_x/Ag films without annealing with that of the films which annealed at 600 and 700 °C, it is found that the intensities of CoPt (0 0 1) and CoPt (0 0 2) superlattice lines were reduced after annealing. As the SiN_x content is raised to 50 vol%, the particle size of CoPt is reduced to be about 9 nm.