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1.
《Surface science》1989,219(3):L583-L589
We have detected a strong azimuth dependence of the adsorption dynamics of hydrogen on a Pt(110)(1×2) surface. Adsorption on the (1 ×2) reconstructed surface is found to be governed by the (111) microfacets of the missing row structure. Furthermore we have observed a low temperature α-state in the thermal desorption spectra comparable to the α-states for other fcc (110) surfaces.  相似文献   

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We present a first-principles density functional theory study on the structural, electronic and dynamical properties of a novel barium doped graphene phase. Low energy electron diffraction of barium doped graphene presents clear evidence of (2 × 2) spots induced by barium adatoms with BaC8 stoichiometry. First principles calculations reveals that the phase is thermodynamically stable but unstable to segregation towards the competitive BaC6 monolayer phase. The calculation of phonon spectrum confirms the dynamical stability of the BaC8 phase indicating its metastability, probably stabilized by doping and strain conditions due to the substrate. Barium induces a relevant doping of the graphene π states and new barium-derived hole Fermi surface at the M-point of the (2 × 2) Brillouin zone. In view of possible superconducting phase induced by foreign dopants in graphene, we studied the electron–phonon coupling of this novel (2 × 2) obtaining λ = 0.26, which excludes the stabilization of a superconducting phase.  相似文献   

4.
Kinetic energy distributions of muonic hydrogen atoms μp(1S) have been obtained by means of a time-of-flight technique for hydrogen gas pressures between 4 and 64 hPa. A high energy component of ∼900 eV observed in the data is interpreted as the signature of long-lived μp(2S) atoms, which are quenched in a non-radiative process leading to the observed high energy: the collision of a thermalized μp(2S) atom with a hydrogen molecule H2 results in the resonant formation of a {[(ppμ)+]*pee}* molecule. Then the (ppμ)+ complex undergoes Coulomb de-excitation and the ∼1.9 keV excitation energy is shared between a μp(1S) atom and one proton. The preliminary analysis of the time spectra gives a long-lived μp(2S) population of ∼1% of all stopped muons, and a quenching rate of ∼4⋅1011 s−1. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

5.
The problem of calculating the vibrations of the F(HF)2]? complex with hydrogen bonds is considered with allowance for the anharmonicity and interaction of motions in different degrees of freedom. A systematic solution of this problem is proposed which consists in separating the total vibrational system into subsystems, obtaining sufficiently exact vibrational wave functions of subsystems, and expanding the vibrational wave functions of the total system in basis functions constructed from the wave functions of subsystems. At the first stage of our study, the stretching and bending modes of two F...HF hydrogen bonds are considered with the use of an exact kinetic energy operator and a nonempirical three-dimensional potential energy surface. It is shown that these vibrational modes of the complex are characterized by significant mechanical and electric anharmonicities. The calculated values of frequencies of the symmetric and antisymmetric vibrations of hydrogen bonds are in good agreement with the experimental findings.  相似文献   

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Gasparov  V. A.  Audouard  A.  Drigo  L.  Schlueter  J. A. 《JETP Letters》2019,110(1):74-78
JETP Letters - We present upper critical magnetic fields data for κ(BEDT-TTF)2Cu[N(CN)2]Br (hereafter k-Br), single crystals with the magnetic field applied either or perpendicular and...  相似文献   

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A few red degraded bands attributable to NS have been reported earlier byFowler andBarker, Dressler andBarrow et al, and they occur in the same region (2300 to 2700 Å) as the bands of the known systems (C 2 +?X 2 П) and (A 2 Δ?X 2 П). Measurements made on the heads of some of these weak bands ledBarrow et al. to believe that these bands may form a system analogous to theβ-system of NO and be due to a2 П-2 П transition. The spectrum of NS has now been studied in a little more detail by means of an uncondensed discharge through dry nitrogen and sulphur vapour in the presence of argon and thirty three bands belonging to this system have been recorded in the region 2280 to 2760 Å. It has been found possible to represent the band heads by means of the equation
$$^v {\text{head}} {\text{ = }} \left. {_{43182 \cdot 5}^{{\text{43311}} \cdot {\text{5}}} } \right\}_{ - [1219 \cdot 20(v'' + \tfrac{1}{2}) - 7 \cdot 48(v'' + \tfrac{1}{2})^2 ].}^{ + [761 \cdot 04(v' + \tfrac{1}{2}) - 5 \cdot 10(v' + \tfrac{1}{2})^2 ]}$$  相似文献   

10.
The equations of motion are worked out for the atoms of a semi-infinite crystal covered with a commensurate adsorbate by using the clean crystal as a basis. This procedure produces a complete set of displacement fields consistent with the relevant space-group symmetry. These equations are solved with help of the matching procedure to give the surface even phonon and resonance dispersion curves in the (010) direction of Ni(1OO) covered with a C(2×2) oxygen overlayer. The consequences of the adsorbate induced folding of the Brillouin zone upon the bulk and surface phonons are analysed. Using symmetry adapted coordinates secures a straightforward identification of the loss features observed by EELS.  相似文献   

11.
We have determined the electron-coupling spectrum of superconducting Bi2Sr2CaCu2O(8+δ) from high-resolution angle-resolved photoemission spectra by two deconvolution-free robust methods. As hole concentration decreases, the coupling spectral weight at low energies ?15 meV shows a twofold and nearly band-independent enhancement, while that around ~65 meV increases moderately, and that in ?130 meV decreases leading to a crossover of dominant coupling excitation between them. Our results suggest the competition among multiple screening effects, and provide important clues to the source of sufficiently strong low-energy coupling, λ(LE)≈1, in an underdoped system.  相似文献   

12.
The CF(X2Π) radical has been re-investigated with vacuum ultraviolet photoelectron spectroscopy. Two bands were observed and assigned to the ionisations CF+(X1Σ+)←CF(X2Π) and CF+(a3Π)← CF(X2Π). The first band, which has been observed previously, has an adiabatic ionisation energy of (9.11±0.02) eV and a vertical ionisation energy of (9.55±0.02) eV. For the second band, three vibrational components were observed with the first, the most intense, at an ionisation energy of (13.94±0.02) eV. Analysis of the vibrational structure in the two observed bands allowed ωe and re to be determined as 1810±30 cm−1 and 1.154±0.005 Å, respectively for the first ionic state, CF+(X1Σ+), and 1614±30 cm−1 and 1.213±0.005 Å, respectively for the second ionic state, CF+(a3Π). Comparison of the ionisation energies and spectroscopic constants obtained has been made with values obtained from recent multi-reference configuration interaction calculations.  相似文献   

13.
The electron paramagnetic resonance (EPR) parameters (g factors gx, gy, gz and hyperfine structure constants Ax, Ay, Az) for Cu2+ in (NH4)2Mg(SO4)2·6H2O (DHMS) crystal are theoretically investigated using the high-order perturbation formulas of these parameters. In the calculations, the ligand orbital and spin–orbit coupling for the impurity Cu2+ are taken into account; the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the EPR parameters with the local structure of the impurity center. The ligand orbital and the spin–orbit coupling contributions are included on the basis of the cluster approach. Based on the calculation, the theoretical EPR parameters show good agreement with the observed values. The results are discussed.  相似文献   

14.
(13)C nuclear magnetic resonance measurements were performed on κ-(BEDT-TTF)(2)Cu(NCS)(2), with the external field placed parallel to the quasi-2D conducting layers. The absorption spectrum is used to determine the electronic spin polarization M(s) as a function of external field H at a temperature T=0.35 K. A discontinuity in the derivative dM(s)/dH at an applied field of H(s)=213±3 kOe is taken as evidence for a Zeeman-driven transition within the superconducting state and stabilization of inhomogeneous superconductivity.  相似文献   

15.
ABSTRACT

Raman spectra of the uranyl-containing mineral coconinoite, Fe2Al2(UO2)2(PO4)4(SO4)(OH)2 · 20H2O, are presented and compared with the mineral's infrared spectra. Bands connected with (UO2)2+, (PO4)3?, (SO4)2?, (OH)?, and H2O stretching and bending vibrations are assigned. Approximate U?O bond lengths in uranyl, (UO2)2+, and O?H…O hydrogen bond lengths are calculated from the wavenumbers of the U?O stretching vibrations and (OH)? and H2O stretching vibrations, respectively, and compared with published data for similar natural and synthetic compounds.  相似文献   

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The infrared spectrum of the ν4(E) and 2ν2(A1) bands of 12CD3F have been recorded and deconvolved to ∼0.005 cm−1 resolution. More than 1890 transitions have been assigned to one of the 37 subbands (−18≤KΔK≤+18) comprising the spectrum of the ν4 band with a maximum assigned J value of 41. The weak 2ν2(A1) band has never been reported in the infrared prior to this work. A total of 358 transitions in K ≤ 8 subbands have been assigned to the 2ν2 band. The two bands are members of the 24 interacting state complex of 12CD3F spectra in the 5-μm region. The ν4 and 2ν2 spectra are highly perturbed, exhibiting local and global resonances. Effective parameters of the two bands were obtained by fitting the data in a restricted manner leaving out the obviously perturbed transitions. The effective parameters, the identification of the different resonances affecting the bands, and estimates of some of the coupling constants are reported.  相似文献   

18.
This paper reports that the actual fluorescence lifetime 7.64±0.06ns of a10%-glyoxal water solution is determined for the first time from the laser-induced fluores-cence decay curve detected by the system with a response time in the order of magnitude ofnanosecond and processed by deconvolution on combination with phase plane method and iter-ative convolution method.The experimental method presented in this paper is regarded as aneffective method for measuring the fluorescence lifetime in nanoseconds or even in sub-nanoseconds by means of a detecting system with an order of magnitude of nanosecond.  相似文献   

19.
The hadronic decays ,and ωf2(1270) have been studied in a sample of 1.27 million produced.Measurements of their branching fractions are presented. While obeys the "14% rule" predicted by theory, →ωf2 (1270) is suppressed comparing with the corresponding decay. As a vector-tensor pair combination, the ωf2 mode is the first example of a non-vector-pseudoscalar decay of charmonium which violates the above mentioned rule.  相似文献   

20.
Electronic absorption spectra and photoacoustic spectra of four copper(II)-amino acid complexes of formulas Cu(L-met)˙(1). Cu(DL-met)˙(2). Cu(L-ala)x(3) and Cu(DL-ala)˙-H2O(4)(L-met=L-methioninato;DL-met=DL-methioninato;L-ala=L-alaninato DL-ala=DL-alaninato) were recorded and the results are discussed quantitatively with respect to llgand field theory and the radical wave function of a non-free copper(II) ion. The relationship between the maximum absorption peak in PAS and magnetic properties is also discussed. Lastly, a qualitative explanation on the senquence of splitting energy in going from regular octahedral to strongly elongately and slightly tetragonally distorted octahedral around each copper(II) center is proposed.  相似文献   

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