Absolute Intensities Measurements in the nu(4) + nu(5) Band of (12)C(2)H(2): Analysis of Herman-Wallis Effects and Forbidden Transitions

We measured absolute line intensities in two bands of (12)C(2)H(2) near 7.5 μm, namely the nu(4) + nu(5)(Sigma(+)(u))-0(Sigma(+)(g)) and nu(4) + nu(5)(Delta(u))-0(Sigma(+)(g)) bands, using Fourier transform spectroscopy with an accuracy estimated to be better than 2%. Using theoretical predictions from Watson [J. K. G. Watson, J. Mol. Spectrosc. 188, 78 (1998)], the observation of the forbidden nu(4) + nu(5)(Delta(u))-0(Sigma(+)(g)) band and the Herman-Wallis behavior exhibited by its rotational lines were studied quantitatively in terms of two types of interactions affecting the levels involved by the band: l-type resonance and Coriolis interaction. In the case of the nu(4) + nu(5)(Sigma(+)(u))-0(Sigma(+)(g)) band, the influence of l-type resonance is also confirmed. We also attributed the intensity asymmetry observed between the R and P branches of that latter band to a Coriolis interaction with l = 1 levels. We did not observe the nu(4) + nu(5)(Sigma(-)(u))-0(Sigma(+)(g)) band, consisting only of a Q branch, in agreement with Watson's prediction. Copyright 2000 Academic Press.     

High-Resolution Analysis of the nu(4) Absorption Band of CH(2)(79)BrF

The gas-phase infrared spectrum of the nu(4) fundamental band of CH(2)(79)BrF was recorded in the 1010-1116 cm(-1) wavenumber region using a TDL spectrometer. In this first high-resolution investigation of the synthesized (79)Br isotopic form, more than 10 200 transitions of this a/b-hybrid band centered at 1068.5385 cm(-1) were assigned and, using the Watson's A-reduced Hamiltonian in the I(r)-representation, a reliable set of molecular constants for the excited state v(4) = 1 was determined. From ground state combination differences having rotational quantum numbers J and K(a) up to 97 and 21, respectively, improved and extended ground state rotational and centrifugal distortion constants were calculated as well. Comparison between the observed and calculated band intensities in appropriate regions of the spectrum gave an estimate of the transition dipole-moment ratio along the a and b axes as ||Deltaμ(a)/Deltaμ(b) || = 2.0 +/- 0.2, in agreement with the predicted theoretical value of 1.99. Copyright 2000 Academic Press.     

The Significance of the Δkl Parameters in the Vibration-Rotational Energies of Diatomic Molecules

We discuss the physical significance of the parameters Δ_kl that arise from mostly the adiabatic and nonadiabatic effects in the vibration-rotational energles of diatomic molecules for which data from isotopic variants are available. Examples are given of the use c f these parameters to derive radial functions for HC1 and LiH. Similar to those for the U_kl coefficients, relations among the Δ_kl coefficients have been developed, but caution is urged in their use.     

Frequency Measurement of Pure Rotational Transitions of D(2)O from 0.5 to 5 THz

Frequencies of pure rotational transitions of D(2)O were measured in the region 0.5-5 THz with a high-precision far-infrared spectrometer using a tunable radiation source. Measured frequencies of about 150 spectral lines, 30 of them being newly measured lines, provide an excellent frequency standard for the far-infrared region together with our previous measurements on H(2)(16)O, H(2)(17)O, and H(2)(18)O. Molecular parameters of Watson's A-reduced Hamiltonian have been obtained to reproduce the observed frequencies. Copyright 2001 Academic Press.     

Periodic solution and chaotic strange attractor for shunting inhibitory cellular neural networks with impulses

By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence, uniqueness, and global exponential stability of periodic solution for shunting inhibitory cellular neural networks with impulses, dx(ij)dt=-a(ij)x(ij)- summation operator(C(kl)inN(r)(i,j))C(ij) (kl)f(ij)[x(kl)(t)]x(ij)+L(ij)(t), t>0,t not equal t(k); Deltax(ij)(t(k))=x(ij)(t(k) (+))-x(ij)(t(k) (-))=I(k)[x(ij)(t(k))], k=1,2,...] . Furthermore, the numerical simulation shows that our system can occur in many forms of complexities, including periodic oscillation and chaotic strange attractor. To the best of our knowledge, these results have been obtained for the first time. Some researchers have introduced impulses into their models, but analogous results have never been found.     

The Coriolis Interaction between the nu(9) and nu(7) Fundamental Bands of Methylene Fluoride

The infrared spectrum of the nu(12) fundamental band of ethylene (C(2)H(4)) has been measured with an unapodized resolution of 0.004 cm(-1) in the frequency range of 1380-1500 cm(-1) using the Fourier transform technique. By assigning and fitting a total of 1387 infrared transitions using a Watson's A-reduced Hamiltonian in the I(r) representation, rovibrational constants for the upper state (v(12) = 1) up to five quartic and three sextic centrifugal distortions terms were derived. They represent the most accurate constants for the band so far. The rms deviation of the fit was 0.00033 cm(-1). The A-type nu(12) band with a band center at 1442.44299 +/- 0.00003 cm(-1) was found to be relatively free from local frequency perturbations. The inertial defect Delta(12) was found to be 0.24201 +/- 0.00002 u ?(2). Copyright 2000 Academic Press.     

Precise measurement of dp elastic scattering at 270 MeV and three-nucleon force effects

The cross section, the deuteron vector A(d)(y) and tensor analyzing powers A(ij), the polarization transfer coefficients K(y('))(ij), and the induced polarization P(y(')) were measured for the dp elastic scattering at 270 MeV. The cross section and A(d)(y) are well reproduced by Faddeev calculations with modern data-equivalent nucleon-nucleon forces plus the Tucson-Melbourne three-nucleon force. In contrast, A(ij), K(y('))(ij), or P(y(')) are not described by such calculations. These facts indicate the deficiencies in the spin dependence of the Tucson-Melbourne force and call for extended three-nucleon force models.     

Moments of the neutron charge form factor and the N --> Delta quadrupole transition

Recent data allow a new parametrization of the neutron charge form factor GnE. A parameter-free quark-model relation between GnE and the N-->Delta quadrupole form factor G(N-->Delta)C2 is used to predict G(N-->Delta)C2 from GnE data. In particular, is related to N-->Delta quadrupole moment Q(N-->Delta), while connects to the N-->Delta quadrupole transition radius Delta)>. From the latter we derive an experimental value for the charge radius of the light constituent quarks r(gamma(q)) = 0.8 fm. Finally, the C2/M1 ratio in pion electroproduction is predicted from the elastic neutron form factor data.     

Connection between the elastic GEp/GMp and P-->Delta form factors

It is suggested that the falloff in Q2 of the P-->Delta magnetic form factor G*M is related to the recently observed falloff of the elastic electric form factor G(Ep)/G(Mp). Calculation is carried out in the framework of a generalized parton distribution model whose parameters are determined by fitting the elastic form factors F(1p) and F(2p) and isospin symmetry. When applied to the P-->Delta transition with no additional parameters, the shape of G*M is found to exhibit the requisite falloff with Q2.     

An investigation of the structure and bond rotational potential of some fluorinated ethanes by NMR spectroscopy of solutions in nematic liquid crystalline solvents

NMR spectra of 1,2-dibromo-1,1-difluoroethane and 1-bromo-2-iodo-tetrafluoroethane dissolved in nematic liquid crystalline solvents have been analysed to yield the magnitudes and signs of the scalar couplings, J(ij), and total anisotropic couplings, T(ij), between all the (1)H, (19)F, and (13)C nuclei, except for those between two (13)C nuclei. The values obtained for T(ij) in principle contain a contribution from J(ij)(aniso), the component along the static applied magnetic field of the anisotropic part of the electron-mediated spin-spin coupling. Neglecting this contribution allows partially averaged dipolar couplings, D(ij), to be extracted from the T(ij), and these were used to determine the structure, orientational order, and the conformational distribution generated by rotation about the C-C bond. The values obtained are compared with the results of calculations by ab initio and density functional methods. The differences found are no greater than those obtained for similar compounds which do not contain fluorine, so that there is no definitive evidence for significant contributions from J(CF)(aniso) or J(FF)(aniso) in the two compounds studied.     

Non-uniqueness of the heat-current operator and the hopping thermoelectric and thermomagnetic phenomena

The Hardy's corrections to the Maradudin's lattice part of the total heat current operator are shown to yield no corrections to the hopping thermoelectric coefficients of amorphous solids and glasses in the lowest (minus-first) order of the electron phonon coupling constant. But even after including the magnetic field (0, 0,), the lowest non-zero (zeroth order) contributions to the Peltier and Seebeck tensors are shown to be diagonal, yielding thus no contribution to the Nernst and Ettingshaussen coefficients. Therefore, the Hardy corrections, which might yield the next (first) order contributions to these coefficients, appear to be crucial for treating the thermomagnetic phenomena in amorphous and glassy materials.     

Analysis of the nu(12) Band of Ethylene-(13)C(2) by High-Resolution FTIR Spectroscopy

The Fourier transform infrared (FTIR) spectrum of the nu(12) fundamental band of ethylene-(13)C(2) ((13)C(2)H(4)) was recorded with an unapodized resolution of 0.004 cm(-1) in the frequency range from 1380 to 1500 cm(-1). Rovibrational constants for the upper state (nu(12)=1) up to five quartic and three sextic centrifugal distortion terms were derived for the first time by assigning and fitting a total of 1177 infrared transitions using a Watson's A-reduced Hamiltonian in the I(r) representation. The rms deviation of the fit was 0.00045 cm(-1). The ground state rovibrational constants were also determined for the first time by a fit of 738 combination differences from the present infrared measurements, with a rms deviation of 0.00060 cm(-1). The A-type nu(12) band with a band center at 1436.65411+/-0.00005 cm(-1) was found to be relatively free from local frequency perturbations. The inertial defect Delta(12) was found to be 0.24300+/-0.00002 u?(2). Copyright 2001 Academic Press.     

Gapless color-flavor-locked quark matter

In neutral cold quark matter that is so dense that the strange quark mass Ms is unimportant, all three quark flavors pair in a color-flavor locked (CFL) pattern, and all nine fermionic quasiparticles have a gap Delta (or 2Delta). We argue that, as the density decreases (or Ms increases), there is a quantum phase transition (at M(2s/mu approximately 2Delta) to a new "gapless CFL phase" in which only seven quasiparticles have a gap. There is still an unbroken U(1)(Q) gluon/photon, but, unlike CFL, gapless CFL is a Q conductor with gapless (charged) quasiquarks and a nonzero electron density at zero temperature, so its low energy effective theory and astrophysical properties are qualitatively new. At the transition, the dispersion relations of both gapless quasiparticles are quadratic, but for larger M2s/mu, one becomes conventionally linear while the other remains quadratic, up to tiny corrections.     

Auger decay and the direct double ionization probability of a 2p inner-shell hole in a singly charged Ar+ ion

We have performed multi-component full-configuration interaction calculations to investigate the nature of chemical bonding of [LiH;e⁺] at the small and large internuclear distance. We discuss the importance of geometrical changes in positronic compounds induced by a positron attachment in terms of the virial theorem, with a comparison of the adiabatic- and vertical-positron affinity (PA). The systematic improvement of the PA values achieved by optimisation of (i) the molecular geometry and (ii) the positronic basis centre is also discussed. The stable dissociation channel of [LiH;e⁺] is compared with the ionic- and neutral-dissociation channels of its parent molecule LiH through the analysis of the potential energy curve and the electronic and positronic densities. The vertical PA as a function of is also presented, which is the difference between the potential energy curve of the parent molecule (LiH → Li + H) and its positronic compound ([LiH; e⁺] → Li + [H; e⁺]). Unlike the preceding study of [M. Mella et al., J. Chem. Phys. 113, 6154 (2000)], it took more than bohr to converge the vertical PA due to the long-range ionic bonding interaction.     

Investigation of the conjectured nucleon deformation at low momentum transfer

We report new precise H(e,e(')p)pi(0) measurements at the Delta(1232) resonance at Q(2)=0.127 (GeV/c)(2) obtained at the MIT-Bates out-of-plane scattering facility which are particularly sensitive to the transverse electric amplitude (E2) of the gamma(*)N-->Delta transition. The new data have been analyzed together with those of earlier measurements to yield precise quadrupole to dipole amplitude ratios: Re(E(3/2)(1+)/M(3/2)(1+))=(-2.3+/-0.3(stat+syst)+/-0.6(model))% and Re(S(3/2)(1+)/M(3/2)(1+))=(-6.1+/-0.2(stat+syst)+/-0.5(model))% for M(3/2)(1+)=(41.4+/-0.3(stat+syst)+/-0.4(model))(10(-3)/m(pi(+))). The derived amplitudes give credence to the conjecture of deformation in hadrons favoring, at low Q2, the dominance of mesonic effects.     

A theory of vibrational frequency shifts revisited: application to dimers of LiH with the inert gases He,Ne, Ar and Kr

The objective of this paper is to contribute towards an understanding of the anomalous blue vibrational shifts that have been observed on forming some hydrogen bonds. It is shown that linear complexes of the LiH molecule with an inert gas atom Rg exhibit red or blue shifts of the LiH vibrational frequency depending upon whether Rg is attached to the Li or the H atom.

The shifts in the frequency of the Li–H vibration on forming the weakly bound linear complexes Li–H…Rg and H–Li…Rg (Rg?=?He, Ne, Ar, Kr) were determined by ab initio computations at the MP2/6-311++G(2d,?2p) level of theory. These frequency shifts were found to be in good agreement with predictions from a model based on perturbation theory and involving first and second derivatives U′ and U′′ of the interaction energy with respect to displacement of the Li–H bond length from its equilibrium value in the isolated molecule. Concentration of the Li–H vibrational motion in the light H atom causes U′ and U′′ to be dominated by repulsion in Li–H…Rg and by attraction in H–Li…Rg, producing blue and red shifts, respectively. The bond length changes on complexation are well predicted by U′.     

Structural investigations on an amorphous Se90Te10 alloy produced by mechanical alloying using EXAFS, cumulant expansion and RMC simulations

We investigated an amorphous Se(90)Te(10) alloy produced by mechanical alloying using two different approaches. First, we used extended x-ray absorption fine structure (EXAFS) spectroscopy and the cumulant expansion method using the Einstein model for the temperature dependence of the cumulants to obtain the cumulants C(*)(1), C(*)(2), and C(*)(3). From these, we found information about the structure of the alloy as well as the thermal and structural disorder, anharmonicity of the effective interatomic pair potentials, thermal expansion of the Se-Se and Se-Te bonds and asymmetry of the partial distribution functions g(Se-Se)(r) and g(Se-Te)(r). The cumulants C(*)(1), C(*)(2), and C(*)(3) also allowed us to reconstruct the g(EXAFS)(ij)(r,T) functions from EXAFS. Then, we made reverse Monte Carlo (RMC) simulations using the total structure factor S(K) obtained from synchrotron x-ray diffraction and the EXAFS oscillations χ(k) on the Se K edge as input data to obtain the g(RMC)(ij)(r) functions. Both methods furnished very similar g(ij)(r) functions, and the structural data obtained from them were also very similar. The results obtained from both methods showed the presence of Se-Te pairs indicating that there is alloying at the atomic level. In addition, we could not find any evidence of the presence of Te clusters in the alloy.     

High-field quasiparticle tunneling in Bi2Sr2CaCu2O(8+delta): negative magnetoresistance in the superconducting state

We report on the c-axis resistivity rho(c)(H) in Bi(2)Sr(2)CaCu(2)O(8+delta) that peaks in quasistatic magnetic fields up to 60 T. By suppressing the Josephson part of the two-channel (Cooper pair/quasiparticle) conductivity sigma(c)(H), we find that the negative slope of rho(c)(H) above the peak is due to quasiparticle tunneling conductivity sigma(q)(H) across the CuO2 layers below H(c2). At high fields (a) sigma(q)(H) grows linearly with H, and (b) rho(c)(T) tends to saturate ( sigma(c) not equal0) as T-->0, consistent with the scattering at the nodes of the d-wave gap. A superlinear sigma(q)(H) marks the normal state above T(c).     

Elastic constants from microscopic strain fluctuations

Fluctuations of the instantaneous local Lagrangian strain epsilon(ij)(r,t), measured with respect to a static "reference" lattice, are used to obtain accurate estimates of the elastic constants of model solids from atomistic computer simulations. The measured strains are systematically coarse-grained by averaging them within subsystems (of size L(b)) of a system (of total size L) in the canonical ensemble. Using a simple finite size scaling theory we predict the behavior of the fluctuations as a function of L(b)/L and extract elastic constants of the system in the thermodynamic limit at nonzero temperature. Our method is simple to implement, efficient, and general enough to be able to handle a wide class of model systems, including those with singular potentials without any essential modification. We illustrate the technique by computing isothermal elastic constants of "hard" and "soft" disk triangular solids in two dimensions from Monte Carlo and molecular dynamics simulations. We compare our results with those from earlier simulations and theory.     

基态Lin(n=2, 3)结构与完全解析势能函数

使用Gaussian03程序包, 采用全电子单双取代耦合簇(CCSD(full))方法, 选择基组6-311+g(2df) , 对Li2分子的基态进行优化计算, 采用十一参量Murrell-Sorbie函数, 运用最小二乘法拟合得到Li2分子基态解析势能函数, 给出与实验值符合很好的光谱常数; 使用同样的方法和基组, 对Li3分子的基态结构进行优化计算, 得到Li3分子基态平衡结构. 采用多体项展式法, 利用Li3分子平衡结构C2v的几何参数、力常数和离解能, 以及七个线性系数Ci(i=1, 2, 3, 4, 5, 6, 7)与两个非线性系数的函数关系, 进行非线性优化拟合得到两个非线性系数, 进而得到七个线性系数, 得到Li3分子基态完全解析势能函数. 势能面静态特征表明, 该势能函数再现了Li3分子基态全部平衡结构特征.