Study on spectroscopic parameters and molecular constants of HCl(X~1Σ~+) molecule by using multireference configuration interaction approach

Equilibrium internuclear separations, harmonic frequencies and potential energy curves (PECs) of HCl($X^{1}\Sigma ^{ + })$ molecule are investigated by using the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with a series of correlation-consistent basis sets in the valence range. The PECs are all fitted to the Murrell--Sorbie function, and they are used to accurately derive the spectroscopic parameters ($D_{\rm e}$, $D_{0}$, $\omega_{\rm e}\chi_{\rm e}$, $\alpha_{\rm e}$ and $B_{\rm e})$. Compared with the available measurements, the PEC obtained at the basis set, aug-cc-pV5Z, is selected to investigate the vibrational manifolds. The constants $D_{0}$, $D_{\rm e}$, $R_{\rm e}$, $\omega_{\rm e}$, $\omega_{\rm e}\chi_{\rm e}$, $\alpha_{\rm e}$ and $B_{\rm e}$ at this basis set are 4.4006~eV, 4.5845~eV, 0.12757~nm, 2993.33~cm$^{ - 1}$, 52.6273~cm$^{ - 1}$, 0.2981~cm$^{ - 1}$ and 10.5841~cm$^{ - 1}$, respectively, which almost perfectly conform to the available experimental results. With the potential determined at the MRCI/aug-cc-pV5Z level of theory, by numerically solving the radial Schr\"{o}dinger equation of nuclear motion in the adiabatic approximation, a total of 21 vibrational levels are predicted. Complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced, which are in excellent agreement with the available Rydberg--Klein--Rees data. Most of these theoretical vibrational manifolds are reported for the first time to the best of our knowledge.     

Parameter extraction for a Ti/4H-SiC Schottky diode

Based on the MIS model, a simple method to extract parameters of SiC Schottky diodes is presented using the $I$-$V$ characteristics. The interface oxide capacitance $C_\i$ is extracted for the first time, as far as we know. Parameters of 4H-SiC Schottky diodes fabricated for testing in this paper are: the ideality factor $n$, the series resistance $R_{\rm s}$, the zero-field barrier height $\phi_{\rm B0}$, the interface state density $D_{\rm it}$, the interface oxide capacitance $C_\i$ and the neutral level of interface states $\phi_0$.     

The splitting of low-lying states for hydroxyl molecule under spin--orbit coupling

The splitting of potential energy curves for the states $X^{2}\Pi _{3/2}$, $^{2}\Pi _{1/2}$ and $A^{2}\Sigma ^{ +}$ of hydroxyl OH under spin--orbit coupling (SOC) has been calculated by using the SO multi-configuration quasi-degenerate perturbation theory (SO-MCQDPT). Their Murrell--Sorbie (M--S) potential functions have been derived, then, the spectroscopic constants for $X^{2}\Pi _{3/2}$,$^{ 2}\Pi _{1/2}$ and $A^{2}\Sigma ^{ + }$ have been derived from the M--S function. The calculated dissociation energies for the three states are $D_{0}$[OH($X^{2}\Pi _{3/2})$]=34966.632cm$^{-1}$, $D_{0}$[OH($^{2}\Pi _{1/2})$]=34922.802cm$^{-1}$, and $D_{0}$[OH($A^{2}\Sigma ^{ + })$]=17469.794cm$^{-1}$, respectively. The vertical excitation energy $\nu [ {{ }^2\Pi _{1/2} ( {\nu = 0} ) \to {X}{ }^2\Pi _{3/2} ( {\nu = 0} )} ] = 139.6{\rm cm}^{-{\rm 1}}$. All the spectroscopic data for the $X^{2}\Pi _{3/2}$ and $^{2}\Pi _{1/2 }$ are given for the first time except the dissociation energy of $X^{2}\Pi _{3/2}$.     

Critical radius and dipole polarizability for a confined system

The analytical transfer matrix method (ATMM) is applied to calculating the critical radius $r_{\rm c}$ and the dipole polarizability $\alpha_{\rm d}$ in two confined systems: the hydrogen atom and the Hulth\'{e}n potential. We find that there exists a linear relation between $r_{\rm c}^{1/2}$ and the quantum number $n_{r}$ for a fixed angular quantum number $l$, moreover, the three bounds of $\alpha_{\rm d}$ ($\alpha_{\rm d}^{K}$, $\alpha_{\rm d}^{B}$, $\alpha_{\rm d}^{U}$) satisfy an inequality: $\alpha_{\rm d}^{K}\leq\alpha_{\rm d}^{B}\leq\alpha_{\rm d}^{U}$. A comparison between the ATMM, the exact numerical analysis, and the variational wavefunctions shows that our method works very well in the systems.     

Observation of four-wave mixing in caesium atoms using a noncycling transition

In this paper the generation of four-wave mixing (FWM) signal using a noncycling transition of caesium atoms is investigated when the pumping laser is locked to the transition $6{\rm S}_{1/2}F=4\to6{\rm P}_{3/2}F'=4$, and meanwhile the probe frequency is scanned across the $6{\rm S}_{1/2}F=4 \to6{\rm P}_{3/2}$ transition. The efficiency of the four-wave mixing signal as a function of the intensity of the pumping beams and the detuning of the pumping beams is also studied. In order to increase the detection efficiency, a repumping laser which is resonant with $6{\rm S}_{1/2} F=3\to 6{\rm P}_{3/2}F'=4$ transition is used. A theoretical model is also introduced, and the theoretical results are in qualitative agreement with experimental ones.     

Characteristics and parameter extraction for NiGe/n-type Ge Schottky diode with variable annealing temperatures

Current transport mechanism in Ni-germanide/n-type Ge Schottky diodes is investigated using current--voltage characterisation technique with annealing temperatures from 300~\duto 500~\du. Based on the current transport model, a simple method to extract parameters of the NiGe/Ge diode is presented by using the $I$--$V$ characteristics. Parameters of NiGe/n-type Ge Schottky diodes fabricated for testing in this paper are as follows: the ideality factor $n$, the series resistance $R_{\rm s}$, the zero-field barrier height $\phi _{\rm b0}$, the interface state density $D_{\rm it}$, and the interfacial layer capacitance $C_{\rm i}$. It is found that the ideality factor $n$ of the diode increases with the increase of annealing temperature. As the temperature increases, the interface defects from the sputtering damage and the penetration of metallic states into the Ge energy gap are passivated, thus improving the junction quality. However, the undesirable crystallisations of Ni-germanide are observed together with NiGe at a temperature higher than 400~\du. Depositing a very thin ($\sim $1~nm) heavily Ge-doped $n^{+}$ Ge intermediate layer can improve the NiGe film morphology significantly.     

Ab initio calculation of accurate dissociation energy, potential energy curve and dipole moment function for the A1∑ + state 7LiH molecule

The reasonable dissociation limit of the A¹∑⁺ state $^{7}$LiH molecule is obtained. The accurate dissociation energy and the equilibrium geometry of this state are calculated using a symmetry-adapted-cluster configuration-interaction method in complete active space for the first time. The whole potential energy curve and the dipole moment function for theA¹∑⁺ state are calculated over a wide internuclear separation range from about 0.1 to 1.4\,nm. The calculated equilibrium geometry and dissociation energy of this potential energy curve are of R_{\e}=0.2487\,nm and D_{\e}=1.064\,eV, respectively. The unusual negative values of the anharmonicity constant and the vibration-rotational coupling constant are of \textit{\omega }_{\e}\textit{\chi }_{\e}=--4.7158cm^{ - 1} and \textit{\alpha }_{\e}=--0.08649cm^{ -1}, respectively. The vertical excitation energy from the ground to the A¹∑⁺ state is calculated and the value is of 3.613\,eV at 0.15875nm (the equilibrium position of the ground state). The highly anomalous shape of this potential energy curve, which is exceptionally flat over a wide radial range around the equilibrium position, is discussed in detail. The harmonic frequency value of 502.47cm¹ about this state is approximately estimated. Careful comparison of the theoretical determinations with those obtained by previous theories about the A¹∑⁺ state dissociation energy clearly shows that the present calculations are much closer to the experiments than previous theories, thus represents an improvement.     

Stereodynamics study of reactions N(~2D)+HD→NH+D and ND+H

The product polarizations of the title reactions are investigated by employing the quasi-classical trajectory (QCT) method. The four generalized polarization-dependent differential cross-sections (PDDCSs) $({2\pi } / \sigma )(\d\sigma _{00} / \d\omega _t )$, $({2\pi } / \sigma )(\d\sigma _{20} / \d\omega _t )$, $({2\pi } / \sigma )(\d\sigma _{22 + } / \d\omega _t )$, and $({2\pi } / \sigma )(\d\sigma _{21 - } / \d\omega _t )$ are calculated in the centre-of-mass frame. The distribution of the angle between ${{\bm k}}$ and ${{\bm j^\prime }}$, $P(\theta _r )$, the distribution of the dihedral angle denoting ${{\bm k}}${--}$\bm k^\prime $--$\bm j^\prime $ correlation, $P(\phi _r )$, as well as the angular distribution of product rotational vectors in the form of polar plots $P(\theta _r ,\phi _r )$ are calculated. The isotope effect is also revealed and primarily attributed to the difference in mass factor between the two title reactions.     

The transfer of the quantum correlation from two-mode nonclassical state field to the supercurrents in two distant SQUID rings

We have considered two distant mesoscopic superconducting quantum interference device (SQUID) rings A and B in the presence of two-mode nonclassical state fields and investigated the correlation of the supercurrents in the two rings using the normalized correlation function $C_{\rm AB}$. We show that when the parameter $\alpha$ is very small for the separable state with the density matrix $\hat {\rho } = (\left| {\alpha , - \alpha } \right\rangle \left\langle {\alpha , - \alpha } \right| + \left| { - \alpha ,\alpha } \right\rangle \left\langle { - \alpha ,\alpha } \right|) / 2$ and entangled coherent state (ECS) $\left| u \right\rangle = N_1 (\left| {\alpha , - \alpha } \right\rangle + \left| { - \alpha ,\alpha } \right\rangle )$ fields, the dynamic behaviours of the normalized correlation function $C_{\rm AB}$ are similar, but it is quite different for the entangled coherent state $\left| {u}' \right\rangle = N_2 (\left| {\alpha , - \alpha } \right\rangle - \left| { - \alpha ,\alpha } \right\rangle )$ field. When the parameter $\alpha $ is very large, the dynamic behaviours of $C_{\rm AB}$ are almost the same for the separable state, entangled coherent state $\left| u \right\rangle $ and $\left| {u}' \right\rangle $ fields. For the two-mode squeezed vacuum state field the maximum of $C_{\rm AB}$ increases monotonically with the squeezing parameter $r$, and as $r \to \infty $, $C_{\rm AB} \to 1$. This means that the supercurrents in the two rings A and B are quantum mechanically correlated perfectly. It is concluded that not all the quantum correlations in the two-mode nonclassical state field can be transferred to the supercurrents; and the transfer depends on the state of the two-mode nonclassical state field prepared.     

Autler--Townes doublet in novel sub-Doppler spectra with caesium vapour cell

With a coupling laser locked to caesium 6S$_{1 / 2}$ $F_{\rm g}$=4--6P$_{3 / 2}$ $F_{\rm e}$=5 cycling transition and a co-propagating probe laser scanned across 6S$_{1 / 2}$ $F_{\rm g}$=4--6P$_{3 / 2}$ $F_{\rm e}$=3, 4 and 5 transitions, a novel scheme for sub-Doppler spectra in Doppler-broadened V-type three-level system is demonstrated by detecting the transmission of the coupling laser through a caesium vapour cell. The Autler--Townes doublet in the sub-Doppler spectra of the coupling laser is clearly observed. The effects of coupling laser intensity on the splitting and linewidth of the Autler--Townes doublet are experimentally investigated and the results agree well with theoretical predictions. Taking the multiple hyperfine levels of caesium atom into account, a brief analysis is presented.     

Effect of substrate temperature on the growth and properties of boron-doped microcrystalline silicon films

Highly conductive boron-doped hydrogenated microcrystalline silicon (\mu c-Si:H) films are prepared by very high frequency plasma enhanced chemical vapour deposition (VHF PECVD) at the substrate temperatures $T_{\rm S})$ ranging from 90$^\circ$C to 270$^\circ$C. The effects of $T_{\rm S}$ on the growth and properties of the films are investigated. Results indicate that the growth rate, the electrical (dark conductivity, carrier concentration and Hall mobility) and structural (crystallinity and grain size) properties are all strongly dependent on $T_{\rm S}$. As $T_{\rm S}$ increases, it is observed that 1) the growth rate initially increases and then arrives at a maximum value of 13.3 nm/min at $T_{\rm S}$=210$^\circ$C, 2) the crystalline volume fraction ($X_{\rm c})$ and the grain size increase initially, then reach their maximum values at $T_{\rm S}$=140$^\circ$C, and finally decrease, 3) the dark conductivity ($\sigma _{\rm d})$, carrier concentration and Hall mobility have a similar dependence on $T_{\rm S}$ and arrive at their maximum values at $T_{\rm S}$=190$^\circ$C. In addition, it is also observed that at a lower substrate temperature $T_{\rm S}$, a higher dopant concentration is required in order to obtain a maximum $\sigma _{\rm d}$.     

Structural and thermodynamic properties of wurtzite-type aluminium nitride from first-principles calculations

The lattice parameter, bulk modulus and its pressure derivative of the wurtzite-type aluminium nitride (w-AlN) are investigated by using the Cambridge Serial Total Energy Package (CASTEP) program in the framework of Density Functional Theory (DFT). The calculated results are in good agreement with the available experimental data and other theoretical results. Through the quasi-harmonic Debye model, the dependences of the normalized lattice parameters $a/a_{0}$ and $ c/c_{0}$, axial ratio $c/a$, normalized primitive-cell volume $V/V_{0}$, Debye temperature ${\it\Theta} _{\rm D} $ and heat capacity $C_{\rm V}$ on pressure $P $ and temperature $ T$ are obtained. It is found that the interlayer covalent interactions (Al-N bonds) are more (even a little) sensitive to temperature and pressure than intralayer ones (N--N bonds), which gives rise to a little lattice anisotropy in the w-AlN.     

Calculation of Rydberg energy levels for the francium atom

Based on the weakest bound electron potential model theory, the Rydberg energy levels and quantum defects of the $np^{2}$P$^{\circ}_{1 / 2}$ ($n$ = 7--50) and $np^{2}$P$^{\circ}_{3 / 2}$ ($n$ =7--50) spectrum series for the francium atom are calculated. The calculated results are in excellent agreement with the 48 measured levels, and 40 energy levels for highly excited states are predicted.     

First principle study of nitrogen vacancy in aluminium nitride

In the framework of density functional theory, using the plane-wave pseudopotential method, the nitrogen vacancy ($V_{\rm N})$ in both wurtzite and zinc-blende AlN is studied by the supercell approach. The atom configuration, density of states, and formation energies of various charge states are calculated. Two defect states are introduced by the defect, which are a doubly occupied single state above the valance band maximum (VBM) and a singly occupied triple state below the conduction band minimum (CBM) for wurtzite AlN and above the CBM for zinc-blende AlN. So $V_{\rm N}$ acts as a deep donor in wurtzite AlN and a shallow donor in zinc-blende AlN. A thermodynamic transition level $E({3 + } \mathord{\left/ {\vphantom {{3 + } + }} \right. \kern-\nulldelimiterspace} + )$ with very low formation energy appears at 0.7 and 0.6eV above the VBM in wurtzite and zinc-blende structure respectively, which may have a wide shift to the low energy side if atoms surrounding the defect are not fully relaxed. Several other transition levels appear in the upper part of the bandgap. The number of these levels decreases with the structure relaxation. However, these levels are unimportant to AlN properties because of their high formation energy.     

New two-fold integration transformation for the Wigner operator in phase space quantum mechanics and its relation to operator ordering

Using the Weyl ordering of operators expansion formula (Hong-Yi Fan, \emph{ J. Phys.} A {\bf 25} (1992) 3443) this paper finds a kind of two-fold integration transformation about the Wigner operator $\varDelta \left( q',p'\right) $ ($\mathrm{q}$-number transform) in phase space quantum mechanics, $\iint_{-\infty}^{\infty}\frac{{\rm d}p'{\rm d}q'}{\pi }\varDelta \left( q',p'\right) \e^{-2\i\left( p-p'\right) \left( q-q'\right) }=\delta \left( p-P\right) \delta \left( q-Q\right),$ and its inverse% $ \iint_{-\infty}^{\infty}{\rm d}q{\rm d}p\delta \left( p-P\right) \delta \left( q-Q\right) \e^{2\i\left( p-p'\right) \left( q-q'\right) }=\varDelta \left( q',p'\right),$ where $Q,$ $P$ are the coordinate and momentum operators, respectively. We apply it to study mutual converting formulae among $Q$--$P$ ordering, $P$--$Q$ ordering and Weyl ordering of operators. In this way, the contents of phase space quantum mechanics can be enriched. The formula of the Weyl ordering of operators expansion and the technique of integration within the Weyl ordered product of operators are used in this discussion.     

Lowest- Q2 measurement of the γp → Δ reaction: Probing the pionic contribution

To determine nonspherical angular-momentum amplitudes in hadrons at long ranges (low Q²), data were taken for the p(ˉe, e'p)π⁰ reaction in the Δ region at Q ² = 0.060 (GeV/c)² utilizing the magnetic spectrometers of the A1 Collaboration at MAMI. The results for the dominant transition magnetic dipole amplitude and the quadrupole to dipole ratios at W = 1232 MeV are , Re( )%, and Re( )%. These disagree with predictions of constituent quark models but are in reasonable agreement with lattice calculations with nonlinear (chiral) pion mass extrapolations, with chiral effective field theory, and with dynamical models with pion cloud effects. These results confirm the dominance, and general Q² variation, of the pionic contribution at large distances.     

Design of surface emitting distributed feedback quantum cascade laser with single-lobe far-field pattern and high outcoupling efficiency

A 7.8-$\mu $m surface emitting second-order distributed feedback quantum cascade laser (DFB QCL) structure with metallized surface grating is studied. The modal property of this structure is described by utilizing coupled-mode theory where the coupling coefficients are derived from exact Floquet--Bloch solutions of infinite periodic structure. Based on this theory, the influence of waveguide structure and grating topography as well as device length on the laser performance is numerically investigated. The optimized surface emitting second-order DFB QCL structure design exhibits a high surface outcoupling efficiency of 22{\%} and a low threshold gain of 10~cm$^{ - 1}$. Using a {$\pi $} phase-shift in the centre of the grating, a high-quality single-lobe far-field radiation pattern is obtained.     

Comparative study of different properties of GaN films grown on(0001) sapphire using high and low temperature AlN interlayers

Comparative study of high and low temperature AlN interlayers and their roles in the properties of GaN epilayers prepared by means of metal organic chemical vapour deposition on (0001) plane sapphire substrates is carried out by high resolution x-ray diffraction, photoluminescence and Raman spectroscopy. It is found that the crystalline quality of GaN epilayers is improved significantly by using the high temperature AlN interlayers, which prevent the threading dislocations from extending, especially for the edge type dislocation. The analysis results based on photoluminescence and Raman measurements demonstrate that there exist more compressive stress in GaN epilayers with high temperature AlN interlayers. The band edge emission energy increases from 3.423~eV to 3.438~eV and the frequency of Raman shift of $E_{2 }$(TO) moves from 571.3~cm$^{ - 1}$ to 572.9~cm$^{ - 1}$ when the temperature of AlN interlayers increases from 700~$^{\circ}$C to 1050~$^{\circ}$C. It is believed that the temperature of AlN interlayers effectively determines the size, the density and the coalescence rate of the islands, and the high temperature AlN interlayers provide large size and low density islands for GaN epilayer growth and the threading dislocations are bent and interactive easily. Due to the threading dislocation reduction in GaN epilayers with high temperature AlN interlayers, the approaches of strain relaxation reduce drastically, and thus the compressive stress in GaN epilayers with high temperature AlN interlayers is high compared with that in GaN epilayers with low temperature AlN interlayers.     

Improved calculation of relic gravitational waves

In this paper, we have improved the calculation of the relic gravitational waves (RGW) in two aspects. First, we investigate the transfer function by taking into consideration the redshift-suppression effect, the accelerating expansion effect, the damping effect of free-streaming relativistic particles, and the damping effect of cosmic phase transition, and give a simple approximate analytic expression, which clearly illustrates the dependence on the cosmological parameters. Second, we develop a numerical method to calculate the primordial power spectrum of RGW in a very wide frequency range, where the observed constraints on $n_{\rm s}$ (the scalar spectral index) and $P_{\rm S}(k_0)$ (the amplitude of primordial scalar spectrum) and the Hamilton--Jacobi equation are used. This method is applied to two kinds of inflationary models, which satisfy the current constraints on $n_{\rm s}$, $\alpha$ (the running of $n_{\rm s}$) and $r$ (the tensor--scalar ratio). We plot them in the $r-{\it\Omega}_{\rm g}$ diagram, where ${\it\Omega}_{\rm g}$ is the strength of RGW, and study their measurements from the cosmic microwave background (CMB) experiments and laser interferometers.     

Investigation of the characteristics of GIDL current in 90nm CMOS technology

A specially designed experiment is performed for investigating gate-induced drain leakage (GIDL) current in 90nm CMOS technology using lightly-doped drain (LDD) NMOSFET. This paper shows that the drain bias $V_{\rm D}$ has a strong effect on GIDL current as compared with the gate bias $V_{\rm G}$ at the same drain--gate voltage $V_{\rm DG}$. It is found that the difference between $I_{\rm D}$ in the off-state $I_{\rm D}-V_{\rm G}$ characteristics and the corresponding one in the off-state $I_{\rm D}-V_{\rm D}$ characteristics, which is defined as $I_{\rm DIFF}$, versus $V_{\rm DG}$ shows a peak. The difference between the influences of $V_{\rm D}$ and $V_{\rm G}$ on GIDL current is shown quantitatively by $I_{\rm DIFF}$, especially in 90nm scale. The difference is due to different hole tunnellings. Furthermore, the maximum $I_{\rm DIFF }$($I_{\rm DIFF,MAX})$ varies linearly with $V_{\rm DG}$ in logarithmic coordinates and also $V_{\rm DG}$ at $I_{\rm DIFF,MAX}$ with $V_{\rm F}$ which is the characteristic voltage of $I_{\rm DIFF}$. The relations are studied and some related expressions are given.