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71.
H.E. Gillis Singbeil W.D. Anderson R.Wellington Davis M.C.L. Gerry E.A. Cohen H.M. Pickett F.J. Lovas R.D. Suenram 《Journal of Molecular Spectroscopy》1984,103(2):466-485
To permit atmospheric monitoring of the molecule, the microwave spectra of two isotopic species of hypochlorous acid, HOCl, have been measured in the frequency range 8–650 GHz. Three b-type branches and an a-type Q branch have all been measured for the first time; improved measurements have been made for the a-type R branches. The analysis has included combination differences of earlier high-resolution infrared spectra to give accurate values for all rotational constants, five quartic and five higher degree centrifugal distortion constants, as well as the chlorine nuclear quadrupole and spin-rotation coupling constants. From the Stark effect, accurate values have also been obtained for both components of the molecular dipole moment. A table of transition frequencies of potential use in atmospheric monitoring is presented. 相似文献
72.
Charge disproportionation (CD) and spin differentiation in Na(1/2)CoO2 are studied using the correlated band local-density approximation + Hubbard U (LDA+U) approach. The simultaneous CD and gap opening seen previously is followed in detail through a first-order charge disproportionation transition 2Co(3.5+)-->Co3++Co4+. Disproportionation in the Co a(g) orbital results in half of the ions (Co3+) becoming electronically and magnetically dead, transforming the quarter-filled a(g) system into a half-filled subsystem that subsequently undergoes the observed charge ordering or metal-insulator transition. Comparing with data in the x approximately 0.3 regime suggests the system has moved into the multiband regime where the effective Coulomb repulsion U-->U(eff)=U/sqrt[3] strongly lessens correlation effects. 相似文献
73.
Two simple examples of spontaneous chiral symmetry breaking are presented. The first is close-packed cylindrically confined spheres. As the cylinder diameter is varied, one obtains a variety of chiral phases. The second example involves unconfined dipolar particles with an isotropic attraction, which also exhibits chiral ground states. We speculate that a dilute magnetorheological fluid film, with the addition of smaller particles to provide an attractive entropic interaction, will exhibit a chiral columnar ground state. 相似文献
74.
Cottaz C Kleiner I Tarrago G Brown LR Margolis JS Poynter RL Pickett HM Fouchet T Drossart P Lellouch E 《Journal of Molecular Spectroscopy》2000,203(2):285-309
Line positions and intensities belonging to the vibrational system 2nu(2)/nu(4) of ammonia (14)NH(3) are measured and analyzed between 1200 and 2200 cm(-1) in order to improve the molecular database. For this, laboratory spectra are obtained at 0.006 and 0.011 cm(-1) unapodized resolution and with 4% precisions for the intensities using Fourier transform spectrometers located at the Kitt Peak National Observatory and the Jet Propulsion Laboratory. The observed data contain transitions of the nu(4) fundamental band near 1626.276(1) and 1627.375(2) cm(-1) (for s and a inversion upper states, respectively) and the 2nu(2) overtone band near 1597.470(3) and 1882.179(5) cm(-1) (for s and a inversion states, respectively). A total of 2345 lines with J' = 15 is assigned from which 2114 line positions with J' = 15 are fitted using an effective rotation-inversion-rotation Hamiltonian to achieve an rms of 0.003 cm(-1) with 57 molecular parameters. Over 1200 intensity measurements are modeled to +/-4.7% using 16 terms of the dipole moment expansion. A dyad model is used in order to model all the interactions expected within the 2nu(2)/nu(4) system. The bandstrengths of 2nu(2) (s <-- a), 2nu(2) (a <-- s), and nu(4) (s <-- s and a <-- a) are estimated to be 6.68(24), 0.201(5), and 116(3) cm(-2) atm(-1), respectively, at 296 K. The prediction generated by this study is available for planetary studies. Copyright 2000 Academic Press. 相似文献
75.
H.M. Pickett E.A. Cohen D.E. Brinza M.M. Schaefer 《Journal of Molecular Spectroscopy》1981,89(2):542-547
Observations and assignments of some of the absorption lines in methanol from 200 to 850 GHz are reported. A simple phenomenological model is described which allows interpretation of spectra and prediction of new lines with little computational effort. 相似文献
76.
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78.
Pogrebnyakov AV Redwing JM Raghavan S Vaithyanathan V Schlom DG Xu SY Li Q Tenne DA Soukiassian A Xi XX Johannes MD Kasinathan D Pickett WE Wu JS Spence JC 《Physical review letters》2004,93(14):147006
We report a systematic increase of the superconducting transition temperature T(c) with a biaxial tensile strain in MgB2 films to well beyond the bulk value. The tensile strain increases with the MgB2 film thickness, caused primarily by the coalescence of initially nucleated discrete islands (the Volmer-Weber growth mode.) The T(c) increase was observed in epitaxial films on SiC and sapphire substrates, although the T(c) values were different for the two substrates due to different lattice parameters and thermal expansion coefficients. We identified, by first-principles calculations, the underlying mechanism for the T(c) increase to be the softening of the bond-stretching E(2g) phonon mode, and we confirmed this conclusion by Raman scattering measurements. The result suggests that the E(2g) phonon softening is a possible avenue to achieve even higher T(c) in MgB2-related material systems. 相似文献
79.
A sharp collective charge excitation is predicted in MgB2 at approximately 2.5 eV for q perpendicular to the boron layers, based on an all-electron analysis of the dynamical density response within time-dependent density functional theory. This novel excitation, consisting of coherent charge fluctuation between Mg and B sheets, induces an abrupt plasma edge in the experimentally observable reflectivity. The existence of this mode reflects the unique electronic structure of MgB2 that is also responsible for strong electron-phonon coupling. By contrast, the acoustic plasmon, recently suggested to explain the high T(c), is not realized when realistic transition strengths are incorporated. 相似文献
80.