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1.
O.-H. Kwon H. Yoo D.-J. Jang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):69-75
While the intercalation of C60 and the formation of C
60
-
in the supercages of NaX and NaY are confirmed by using 129Xe NMR and ESR, the photophysical properties of C60 and C
60
-
are characterized by monitoring transient reflectance spectra and kinetics, fluorescence kinetics, and diffuse reflectance
spectra. C
60
-
is considerably more abundant in NaY than in NaX. This difference is explained in terms of polarity difference between two
zeolites. Both C60 and C
60
-
have remarkably elongated excited-state lifetimes due to their collision-free environment in zeolitic nanocavities although
C
60
-
has much shorter lifetimes than C60. C
60
-
, in particular, shows intense absorption and emission due to its reduced symmetry in zeolites.
Received 13 July 2001 and Received in final form 8 October 2001 相似文献
2.
A. Kanaev L. Museur F. Edery T. Laarmann T. Möller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):261-268
We have studied the fluorescence of electronically excited OH*, H* and H2O+* dissociation fragments after VUV excitation ( h
ν≥11.6
eV) of rare-gas clusters (Rg = Ne, Ar) doped with H2O molecules. In contrast to a free molecule, where Balmer H-series dominate the UV-visible spectra, only the OH
*
(
A
2
Σ
+
↦
X
2
Π) emission band is observed in neon clusters. No emission of excited water ions has been observed. We find that while higher
excitation energies (Ne vs. Ar) induce higher vibrational excitation of the OH*
(
A
) fragment, the rotational temperature is lower. This effect is attributed to the difference in the geometric position of the
H2O molecule on the surface or inside the Rg-cluster. The rotational relaxation in neon clusters is rapid while the vibrational
relaxation is slow because of the coupling with the low energy matrix phonons.
Received 7 March 2002 / Received in final form 27 May 2002 Published online 19 July 2002 相似文献
3.
J. Blasco J. García M.C. Sánchez J. Campo G. Subías J. Pérez-Cacho 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):469-479
Magnetic measurements have been carried out in different LaNi1-xMnxO
3 + δ
samples with 0.1 ⩽
x
⩽ 0.9. All these samples show two magnetic anomalies, one at relatively high temperature characteristic of a ferromagnetic ordering
and the other at low temperature, typical of magnetic relaxation phenomena. Neutron diffraction patterns indicate that long-range
ferromagnetic ordering is only achieved for x
≥ 0.5. Neutron patterns of LaNi0.5Mn0.5O
3 + δ
samples show an ordered arrangement of Ni and Mn atoms in the perovskite lattice. LaNi0.5Mn0.5O
3 + δ
is then, a double perovskite A2BB'O6 whereas Ni and Mn atoms are randomly distributed for the rest of the samples. X-ray magnetic circular dichroism experiments
confirm the presence of collinear ferromagnetism in LaNi0.5Mn0.5O
3 + δ
. The role of competitive magnetic interactions, structural disorder, magnetic anisotropy and magnetic disaccommodation is
also discussed
Received 19 July 2002 / Received in final form 23 October 2002 Published online 31 December 2002 相似文献
4.
S. Broderick L. Degiorgi H.R. Ott J.L. Sarrao Z. Fisk 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):3-6
Intercalation of polyatomic molecules into a superconductor can drastically affect the properties of the compound. A mechanism
responsible for a large increase in T
c for such systems is proposed. It explains the recent remarkable observation of high T
c superconductivity in the hole-doped C60/CHX3 (X≡Cl, Br) compounds and the large shift in their T
c upon Cl↦Br substitution. The increase in T
c is due to contribution to the pairing arising from the interaction of electrons with the vibrational manifold of the molecule.
The proposed mechanism opens up the possibility to observe a site-selective isotope effect. We also suggest that intercalating
CHI3 would further increase the critical temperature to T
c≃ 140 K.
Received 23 January 2002 相似文献
5.
J.E. Lorenzo H. Requardt 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):185-186
Eur. Phys. J. B 24, 315 (2001) Here we comment on a recently published paper on the presence of a phason contribution in the low temperature heat capacity data of the charge-density-wave compounds K0.3MoO3 and (TaSe4)2I. We have shown that the anomaly in the C
P
/
T
3
data reported by Odin et al. is straightforwardly interpreted in terms of low energy phonon modes resulting from the peculiar topology of these compounds.
Received 21 February 2002 Published online 19 July 2002 相似文献
6.
P. Orgiani C. Aruta G. Balestrino S. Lavanga P.G. Medaglia A. Tebano 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):23-28
Transport properties of SrRuO3 thin films were studied as a function of the epitaxial strain. SrRuO3 films were grown on (100) SrTiO3 substrates by the Pulsed Laser Deposition technique equipped with Reflection High Energy Electrons Diffraction (RHEED). Samples
thickness has been varied from a few unit cells to above 1000 ? while monitoring RHEED intensity oscillations. In thicker
films epitaxial strain was found to be progressively relaxed. SrRuO3 relaxed films (thickness 1000 ?) show metallic behavior for the whole temperature range with a ferromagnetic ordering at about 150 K. For thinner
films, ferromagnetic ordering occurs at progressively lower temperatures, until in films thinner than 400 ? it disappears.
Films thinner than 80 ? show a semiconducting behavior at low temperatures. Our results provide direct evidence of the crucial
role of the strain effect for conducting and magnetic properties of SrRuO3.
Received 16 July 2001 and Received in final form 22 October 2001 相似文献
7.
A. Bielski D. Lisak R.S. Trawiński J. Szudy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):217-222
Using a laser-induced fluorescence method a detailed analysis of profiles of the 114Cd 326.1 nm line perturbed by N2 and CH4 was performed which revealed deviations from the ordinary Voigt profile. These deviations are shown to be consistent with
fits of experimental profiles to an asymmetric Voigt profile. Coefficients of the pressure broadening, shift and collision-time
asymmetry are determined and compared with those calculated for van der Waals interaction potential.
Received 29 November 2001 / Received in final form 12 July 2002 Published online 4 February 2003 相似文献
8.
P. Parneix 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):375-383
The isomerization and evaporation processes in the neutral homogeneous (CH3CN)n molecular clusters (n
= 2-7) have been investigated using classical molecular dynamics simulations. The evaporation rate constants and the kinetic energy
release in the dissociation have been analysed as a function of the cluster size and as a function of the internal energy
in the parent cluster. The competition between monomer and dimer ejections has been also carefully studied. All the dynamical
properties in these dissociative processes have been discussed in relation to the static properties of the clusters involved
in the dissociation and also in relation to the solid-liquid like transition which appears in these homogeneous molecular
clusters.
Received 19 November 2002 / Received in final form 5 February 2003 Published online 29 April 2003
RID="a"
ID="a"e-mail: pascal.parneix@ppm.u-psud.fr
RID="b"
ID="b"Laboratoire associé à l'université Paris-Sud. 相似文献
9.
W.T. Wallace R.L. Whetten 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):123-126
Smaller gold-cluster anions, typified by Au
7
-
, adsorb multiple CO molecules in a high-pressure, room-temperature flow-reactor, tending toward previously unknown saturation
compositions, Au7(CO)
4
-
. The weakness of the gold-carbonyl adsorption bond is evidenced indirectly by the high CO partial pressure required and more
directly by the high probability of fragmentation in the field-free flight region of the reflectron-type time-of-flight mass
spectrometer. The analysis of this metastability reveals that the actual distribution fN,M of products Au7(CO)
M
-
in the reactor may be highly non-statistical, e.g. with only even-M species present.
Received 17 April 2001 相似文献
10.
J. Zhao Y. Luo G. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):309-316
Tight-binding model is developed to study the structural and electronic properties of silver clusters. The ground state structures
of Ag clusters up to 21 atoms are optimized by molecular dynamics-based genetic algorithm. The results on small Agn clusters (n = 3-9) are comparable to ab initio calculations. The size dependence of electronic properties such as density of states, s-d band separation, HOMO-LUMO gap, and ionization potentials are discussed. Magic number behavior at Ag2, Ag8, Ag14, Ag18, Ag20 is obtained, in agreement with the prediction of electronic ellipsoid shell model. We suggest that both the electronic and
geometrical effect play significant role in the coinage metal clusters.
Received 7 August 2000 相似文献
11.
F. Duque L.M. Molina M.J. López A. Ma nanes J.A. Alonso 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):285-288
The electronic and atomic structure of Al13H has been studied using Density Functional Theory. Al13H has closed electronic shells. This makes the cluster very stable and suggests that it could be a candidate to form cluster
assembled solids. The interaction between two Al13H clusters was analyzed and we found that the two units preserve their identities in the dimer. A cubic-like solid phase assembled
from Al13H units was then modeled. In that solid the clusters retain much of their identity. Molecular dynamics runs show that the
structure of the assembled solid is stable at least up to 150 K. A favorable relative orientation of the clusters with respect
to their neighbors is critical for the stability of that solid.
Received 21 November 2000 相似文献
12.
E. M. Fernández G. Borstel J. M. Soler L. C. Balbás 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):245-248
The ionic and electronic structure of
(Al2O3)n(Ox)
clusters with n
16 and x
= 0,
1, 2 is studied by means of first principles density functional
calculations, norm-conserving pseudopotentials and a numerical
atomic basis set. The equilibrium geometries have been
determined by total energy minimization, starting with several
initial geometries for each cluster size. The trends obtained
for the atomic arrangements (structural isomers, coordination
numbers, disordered versus
ordered structures, etc.) and the electronic properties
(binding energies, Homo-Lumo gap and dipole moments) are
discussed. For most of the oxidized clusters studied here we
find that the Homo-Lumo gap and the magnitude of dipole moment
of isomeric species can vary drastically. 相似文献
13.
H. Belich O.M. Del Cima M.M. Ferreira Jr. J.A. Helayël-Neto 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):145-155
We start from a parity-breaking MCS QED3 model with spontaneous breaking of the gauge symmetry as a framework for evaluation of the electron-electron interaction
potential and for attainment of numerical values for the e
-
e
-
- bound state. Three expressions ( V
eff
, V
eff
, V
eff
) are obtained according to the polarization state of the scattered electrons. In an energy scale compatible with condensed
matter electronic excitations, these three potentials become degenerated. The resulting potential is implemented in the Schr?dinger
equation and the variational method is applied to carry out the electronic binding energy. The resulting binding energies
in the scale of 10-100 meV and a correlation length in the scale of 10-30 ? are possible indications that the MCS-QED3 model adopted may be suitable to address an eventual case of e
-
e
-
pairing in the presence of parity-symmetry breakdown. The data analyzed here suggest an energy scale of 10-100 meV to fix the breaking of the U
(1)-symmetry.
Received 24 September 2002 / Received in final form 15 January 2003 Published online 1st April 2003
RID="a"
ID="a"e-mail: belich@cbpf.br
RID="b"
ID="b"e-mail: delcima@cbpf.br
RID="c"
ID="c"e-mail: manojr@cbpf.br
RID="d"
ID="d"e-mail: helayel@cbpf.br 相似文献
14.
M. Winkelmann G. Fischer B. Pilawa E. Dormann 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):199-209
Nuclear magnetic resonance (NMR) and relaxation of 63Cu and 65Cu in a powder sample of the heavy-fermion paramagnet CeCu6 is measured and analysed quantitatively. Five different Cu sites are accessible to a detailed analysis. We derive quadrupolar
splitting frequencies, Ce to Cu transferred hyperfine field coupling constants, and transversal as well as longitudinal relaxation
behaviour. Only small relaxation anomalies are observed at the orthorhombic to monoclinic structural phase transition of CeCu6. We point to the different importance of transferred hyperfine interaction and local conduction electron density for static
or dynamic part, respectively, of Cu hyperfine interaction. The different sign of the transferred hyperfine interaction from
Ce3+ to different Cu neighbours reveals the different competing interaction mechanisms, giving rise to the heavy-fermion paramagnetic
behavior of CeCu6.
Received 20 November 2001 相似文献
15.
T. Mazet J. Tobola B. Malaman 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):183-191
The electronic structure of the RFe
6
Ge
6
compounds ( R
=
Sc, Lu, Ti, Zr, Hf and Nb) of HfFe
6
Ge
6
-type structure has been studied using the muffin-tin Korringa-Kohn-Rostoker method in a non-relativistic approach. The chemical
bonding is analyzed based on the l-decomposed site projected densities of states. Spin-dependent changes in the R nd- Fe 3d covalent bond are shown to be responsible for the experimentally observed rise in the Fe moment and hyperfine field upon
increasing the R valency. The limited quantitative agreement between theoretical and experimental values is interpreted as
being due to a non-negligible orbital moment and to a significant asphericity in the spin density at the iron site. The theoretical
results also forecast a strong increase of the Ge(2e) transferred hyperfine field with the R valency.
Received 20 December 2002 Published online 4 June 2003
RID="a"
ID="a"e-mail: Thomas.Mazet@lcsm.uhp-nancy.fr
RID="b"
ID="b"Associé au CNRS (UMR 7555) 相似文献
16.
I. Popov T. Kunze S. Gemming G. Seifert 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):439-446
The preferred adsorption sites and the propensity for a self-organised growth of the molybdenum sulfide cluster Mo6S8 on the Au(111) surface are investigated by density-functional band-structure calculations with pseudopotentials and a plane
wave basis set. The quasi-cubic cluster preferentially adsorbs via a face and remains structurally intact.
It experiences a strong, mostly non-ionic attraction to the surface
at several quasi-isoenergetic adsorption positions. A scan of the potential energy surface exhibits only small barriers between
adjacent strong adsorption sites. Hence, the cluster may move in a potential well with degenerate local energy minima at room
temperature. The analysis of the electronic structure reveals a negligible
electron transfer and S-Au hybridised states, which indicate that the cluster-surface
interaction is dominated by S-Au bonds, with minor contributions from
the Mo atom in the surface vicinity. All results indicate that Mo6S8 clusters
on the Au(111) surface can undergo a template-mediated self-assembly to an ordered inorganic monolayer, which is still redox
active and may be employed as surface-active agent in the integration of noble metal and ionic or biological components within
nano-devices.
Therefore, a classical potential model was developed on the basis of the DFT data,
which allows to study larger cluster assemblies on the Au(111). 相似文献
17.
Magnetism in Rh clusters under hydrostatic deformations 总被引:1,自引:0,他引:1
E.O. Berlanga-Ramırez F. Aguilera-Granja A. Dıaz-Ortiz A. Vega 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):343-349
The magnetic behavior of rhodium clusters RhN (N = 4-38) under hydrostatic deformations was investigated. The starting cluster structures were obtained from an evolutionary
search algorithm applied to a Gupta potential. The spin-polarized electronic structure and related magnetic properties were
calculated using a self-consistent spd tight-binding Hamiltonian within the unrestricted Hartree-Fock approximation. The magnetic behavior was analyzed in terms
of the interdependence between the geometrical parameters and the electronic structure. Anomalous magnetic effects were found
in some cases.
Received 5 August 2002 / Received in final form 10 January 2003 Published online 4 March 2003
RID="a"
ID="a"e-mail: berlanga@dec1.ifisica.uaslp.mx 相似文献
18.
C. Langhammer F. Steglich M. Lang T. Sasaki 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):413-416
We report low-temperature measurements 0.07
K
?
T
? 2 K of the specific heat, C, of the perovskite superconductor Sr2RuO4. Based on a detailed analysis of our data with respect to both sample quality (as measured by T
c
= 0.43
K
- 1.17 K) and magnetic-field dependence, it is shown that the electronic contribution to the specific heat, which contains the desired
information on the gap structure, is superimposed by at least two additional contributions: a Schottky-type hump at T
≈ 0.1 - 0.2 K and a low-temperature upturn in C
/
T at T
< 0.1 K. We discuss possible origins of these additional contributions and their implications for the interpretation of low-temperature
C
(
T
) data.
Received 23 August 2001 相似文献
19.
V. Kumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):227-232
We report the recent findings of metal (M) encapsulated
clusters of silicon from computer experiments based on
ab initio total energy
calculations and a cage shrinkage and atom removal approach. Our
results show that using a guest atom, it is possible to wrap
silicon in fullerenelike (f)
structures, as sp2 bonding is not
favorable to produce empty cages unlike for carbon. Transition M
atoms have a strong bonding with the silicon cage that are
responsible for the compact structures. The size and structure
of the cage change from 14 to 20 Si atoms depending upon the
size and valence of the M atom. Fewer Si atoms lead to
relatively open structures. We find cubic,
f, Frank-Kasper (FK)
polyheral type, decahedral, icosahedral and hexagonal structures
for M@Sin with n = 12-16 and several different M
atoms. The magic behavior of 15 and 16 atom Si cages is in
agreement with experiments. The FK polyhedral cluster,
M@Si16 has an exceptionally large density
functional gap of about 2.35 eV calculated within the
generalized gradient approximation. It is likely to give rise to
visible luminescence in these clusters. The cluster-cluster
interaction is weak that makes such clusters attractive for
cluster assembled materials. Further studies to stabilize
Si20 cage with M = Zr, Ba, Sr, and Pb
show that in all cases there is a distortion of the
f cage. Similar studies on M
encapsulated germanium clusters show FK polyhedral and
decahedral isomers to be more favorable. Also perfect
icosahedral M@Ge12 and
M@Sn12 clusters have been obtained with
large gaps by doping with divalent M atoms. Recent results of
the H interaction with these clusters, hydrogenated silicon
fullerenes as well as assemblies of clusters such as nanowires
and nanotubes are briefly presented. 相似文献
20.
C.M. Dion O. Dulieu D. Comparat W. de Souza Melo N. Vanhaecke P. Pillet R. Beuc S. Milošević G. Pichler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):365-370
We present the results of absorption measurements in a cesium vapor around 630 K, together with photoionization spectra through
a resonance-enhanced two-photon absorption of ultracold cesium dimers created after photoassociation of ultracold cesium atoms.
The maximum efficiency of the ultracold molecule ionization is found for wavelengths where absorption at thermal energies
is the strongest, in agreement with our theoretical simulations of both processes, involving the so-called Cs2 diffuse bands. This result will be helpful for further optimization of such a direct way of detection of ultracold molecules.
Received 13 September 2001 相似文献