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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. Marucci P. Launois R. Moret A. Pénicaud 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):29-34
The phase diagram of the newly synthesized mixed crystal C60-biphenyl is investigated as a function of temperature by single-crystal X-ray scattering. Diffuse scattering investigations
evidencing complex disorder and local order effects are presented. Two phase transitions leading to two different doublings
of the high temperature unit cell are observed, at 212 K and 147 K. The first transition is attributed to the ordering of
twisted biphenyls, which couples to the orientational ordering of the C60 molecules as the temperature decreases. Full ordering of the C60 molecules is achieved below 100 K only, in the low temperature phase. The rich phase diagram of C60-biphenyl is due to the interplay between fullerene and biphenyl ordering phenomena.
Received 31 August 2001 and Received in final form 4 December 2001 相似文献
3.
P. Mélinon F. Tournus B. Masenelli A. Perez M. Pellarin J. Lermé M. Broyer B. Champagnon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):337-340
This paper deals with a new type of SiC bonding where silicon atom seems to bridge C60 molecules. We have studied films obtained by deposition of (C60)nSim clusters prepared in a laser vaporization source. Prior deposition, free ionized clusters were studied in a time-of-flight
mass spectrometer. Mixed clusters (C60)nSim were clearly observed. Abundance and photofragmentation mass spectroscopies revealed the relatively high stability of the
(C60)nSi
n
+
, (C60)nSi
n - 1
+
and (C60)nSi
n - 2
+
species. This observation is in favor of the arrangement of these complexes as polymers where the C60 cages may be bridged by a silicon atom. Free neutral clusters are then deposited onto substrate making up a nanogranular
thin film (≃ 100 nm). The film is probed by Auger and X-ray photoemission spectroscopies, but above all by surface enhanced Raman scattering.
The results suggest an unusual chemical bonding between silicon and carbon and the environment of the silicon atom is expected
to be totally different from the sp3 lattice: ten or twelve carbon neighbors might surround silicon atom. The bonding is discussed to the light of the so-called
fullerene polymerization as observed for pure fullerite upon laser irradiation. This opens a new route for bridging C60 molecules together with an appreciable energy bonding, since the usual van der Waals bonding in fullerite could be replaced
by an ionocovalent bond. Such an assumption must be checked in the future by XAS and EXAFS experiments.
Received 15 November 2000 相似文献
4.
J.U. Andersen C. Gottrup K. Hansen P. Hvelplund M.O. Larsson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(2):189-204
Thermionic emission from hot fullerene anions, CN
-, has been measured in an electrostatic storage ring for even N values from 36 to 96. The decay is quenched by radiative cooling and hence the observations give information on the intensity
of thermal radiation from fullerenes. The experiments are analysed by comparison with a simulation which includes the quantisation
of photon energy and the statistics of emission. Experiments with heating of the molecules with a laser beam confirm the interpretation
of the observations in terms of radiative cooling and give an independent estimate of the cooling rate for C60
-. The measured cooling rates agree in general within a factor of two with the prediction from a classical dielectric model
of a thermal radiation intensity of ∼ 300 eV/s for C60 at 1 400 K, scaling approximately with the 6th power of the temperature and with the number of atoms in the molecule.
Received 12 March 2001 and Received in final form 12 June 2001 相似文献
5.
M. Salluzzo F. Natali C. Aruta M.G. Maglione F. Ricci E. Koller Ø. Fischer N.L. Saini 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):467-472
We report results of a time resolved X-ray Absorption Spectroscopy (XAS) experiment on the oxidation process of epitaxial
Y1(Nd0.05Ba1.95)Cu3Ox superconducting thin films. For the first time Cu K-edge XAS technique has been used to explore local structural changes
around the Cu ions during the oxidation process of a high critical temperature superconducting film. The results show that
during the oxygenation of a tetragonal Y1(Nd0.05Ba1.95)Cu3Ox additional local transitions appear in the orthorhombic I phase, which are not linked to long range order transformations
as shown by in situ X-ray diffraction experiment. New questions concerning the dynamic microscopic process leading to the oxygenation and eventually
to superconductivity of the complex R1+xBa2-xCu3Ox (R = Y or rare earth) compounds arose from these results.
Received 21 December 2001 Published online 25 June 2002 相似文献
6.
M. Abbate J.A. Guevara S.L. Cuffini Y.P. Mascarenhas E. Morikawa 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):203-208
We studied the changes in the electronic structure of SrTi1-xRuxO3 across the metal-insulator transition. The parent compound, SrTiO3, is a well known diamagnetic insulator; whereas the doped compound, SrTi1-xRuxO3, becomes a ferromagnetic metal above x
C
= 0.35. The techniques used in the study were photoemission (PES) and O 1
s X-ray absorption (XAS) spectroscopy. The experimental spectra were analyzed in terms of band structure and Hubbard model
calculations. The PES and XAS spectra of SrTi1-xRuxO3 show the Ru 4
d bands growing in the band gap of SrTiO3 . The analysis in terms of the Hubbard model indicates that the Ti 3
d and Ru 4
d bands are mostly decoupled. This suggests that the metal-insulator transition is a percolation transition like that of metals
embedded in a rare gas matrix. Electron correlation effects are present in this system, but they do not seem to play a major
role in the transition.
Received 10 September 2001 相似文献
7.
Z. Hu M. Knupfer M. Kielwein U.K. Rößler M.S. Golden J. Fink F.M.F. de Groot T. Ito K. Oka G. Kaindl 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):449-453
A strong anisotropic distribution of the holes in Ni 3
d and O 2
p orbitals is observed in the polarization dependent O 1
s and Ni 2
p
3/2
X-ray absorption spectroscopy of the linear-chain nickelate Y2-xCaxBaNiO5 (x
= 0, 0.05, 0.1, 0.2), which demonstrates the one-dimensional nature of the electronic state in these compounds. The holes introduced
by Ca-doping occupy both O 2
p and Ni 3
d orbitals along the NiO5 chains. By comparing the experimental Ni 2
p
3/2
absorption spectra of Y2-xCaxBaNiO5 to those from charge transfer multiplet calculations we can derive the orbital character of the additional holes to be of
∼60% O2
p and ∼40% Ni 3
d.
Received 7 January 2002 相似文献
8.
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
9.
A. Prange C. Dahl H.G. Trüper M. Behnke J. Hahn H. Modrow J. Hormes 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):589-596
X-ray Absorption Near Edge Structure (XANES) spectroscopy, often provides a direct correlation between observed resonances
in the spectrum and molecular bonds in the sample. This can be used as a fingerprint for the presence of a given molecular
environment of the absorber atom in a sample. As the white line is found at similar energy positions for S-C and S-H bonds,
this approach is impossible when both types of bond are present simultaneously, as often in biological systems. To develop
a criterium for the presence of S-H bonds in such samples, reduced glutathione, reduced coenzyme A, cysteine and their corresponding
oxidized forms were investigated using sulfur K-edge XANES, revealing a unique feature at 2 475.8 eV in the respective difference
spectra. To correlate this structure to S-H bonds, H2S and H2S2 were measured, whose difference spectrum also shows a structure at this energy position, whereas it is not present throughout
a variety of C-S-C/C-S-S-C environments. Theoretical investigations suggest its correlation to a Rydberg transition occurring
in the case of a S-H bond. Using this criterium, the presence of S-H bonds is in the purple sulfur bacterium Allochromatium vinosum during oxidation of intracellular accumulated sulfur, is proved, as expected from biological considerations.
Received 1st February 2002 / Received in final form 10 June 2002 Published online 13 September 2002 相似文献
10.
I. Compagnon R. Antoine D. Rayane Ph. Dugourd M. Broyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):365-368
Gas phase Ti-C60 clusters are studied by molecular beam electric deflection. The permanent dipole moment of the TiC60 molecule is determined. It is equal to 8.1±1.5
D. This dipole is due to a transfer of electron from the transition metal atom to the C60 cage. No dipole is observed for Ti(C60)2 molecules. This is in agreement with the symmetrical dumbbell-like structure that has been previously proposed.
Received 22 November 2000 相似文献
11.
E. Gadioli G.F. Steyn F. Albertini C. Birattari M. Cavinato S.H. Connell A.A. Cowley E. Fabrici S.V. Förtsch E. Gadioli Erba J.J. Lawrie M. Pigni J.P.F. Sellschop E. Sideras Haddad 《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):195-212
In this paper we study the emission of 8Begs, B and N fragments in the interaction of 16O ions with 59Co, 93Nb and 197Au at incident energies varying from 6 to 25 MeV/nucleon. The spectra of these fragments, as well as those of C fragments
studied in a previous paper, are dominated at forward angles by a component originating from break-up of 16O. At the higher incident energies break-up occurs after quite a sizeable projectile energy loss. Another mechanism which
dominates at large emission angles, favours the emission of low-energy fragments and is attributed to the coalescence of nucleons
during the cascade of nucleon-nucleon interactions by means of which the excited nuclei produced in the primary two-ion interaction
thermalize.
Received: 21 January 2003 / Accepted: 27 March 2003 / Published online: 5 June 2003 相似文献
12.
G. Durand F. Spiegelmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):237-243
The stability against fragmentation and possible relaxation of the lowest excited states of the Na5F4 cluster (representative of cubic non stoechiometric clusters with an excess sodium atom, also called sodium-tail) is investigated
by means of one-electron pseudopotential calculations with particular reference to photoabsorption processes from the ground
state. Whereas the equilibrium configuration of the ground state has C3v symmetry, the doubly degenerate 12E excited state is affected by a conical intersection and a Jahn-Teller effect associated with the rotation of the sodium
tail around the C3-axis. This yields a “Mexican hat" topology for the lowest sheet with three equivalent Cs minima. Alternatively the 22A1 state has a minimum retaining the C3v symmetry. The dissociation paths of the cluster along the C3-axis into respectively Na4F4 + Na and Na4F3 + NaF are also investigated. Among the former paths, the excited states are found adiabatically stable with respect to the
products. However in the A1 symmetry, fragmentation into NaF exhibits an interesting avoided crossing between configurations correlated respectively
with Na4F3
+ + NaF- and Na4F3 + NaF. Such interaction, similar to the well-known charge exchange processes in elementary molecules might induce non adiabatic
predissociation of the 22A1 state. This mechanism is invoked to explain the differences between R2PI and depletion spectra, correlated with the dissociation
or relaxation of the excited states.
Received 24 March 2000 and Received in final form 11 July 2000 相似文献
13.
A fireball model with time evolution based on transport calculations is used to examine the dilepton emission rate of an ultra-relativistic
heavy-ion collision. A transition from hadronic matter to a quark-gluon plasma at a critical temperature T
C between 130-170 MeV is assumed. We also consider a possible mixed phase scenario. We include thermal corrections to the hadronic
spectra below T
C and use perturbation theory above T
C. The sensitivity of the spectra with respect to the freeze-out temperature, the initial fireball temperature and the critical
temperature is investigated.
Received: 4 August 2000 / Accepted: 14 November 2000 相似文献
14.
A. Gloter V. Serin Ch. Turquat C. Cesari Ch. Leroux G. Nihoul 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(2):179-186
The valency of vanadium, and thus indirectly the oxygen stoichiometry, of V-doped hafnia synthesized under different atmospheres
have been investigated on a nanometer scale by means of electron energy loss spectroscopy (EELS). The EELS V L2,3 spectra are compared with the results of crystal field multiplet calculations and experiments on reference vanadium oxides.
The EELS spectra indicate that V-doped hafnia prepared under reducing (H2) and neutral (Ar) atmosphere are unambiguously substituted with trivalent vanadium atoms leading to the creation of oxygen
vacancies in the structure. On the contrary, stoichiometric (Hf, V)O2 compound (i.e. V4+) is more likely to be stabilized under oxidative (air) atmospheres. We also show that the amount of hybridization alters
for the different compounds studied but may in part be analyzed by high spatially resolved EELS. The crystal field multiplet
calculations particularly indicate that a simple reduction of the Slater integrals gives a good account of the spectral modification
induced by hybridization for the case of tetravalent vanadium atoms.
Received 17 November 2000 and Received in final form 17 April 2001 相似文献
15.
C. Hébert M. Willinger D.S. Su P. Pongratz P. Schattschneider R. Schlögl 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):407-414
Band-structure (BS) calculations of the density of states (DOS) using the full potential augmented plane waves code WIEN97
were performed on the four single-valence vanadium oxides VO, V2O3, VO2 and V2O5. The DOS are discussed with respect to the distortions of the VO6 octahedra, the oxidation states of vanadium and the orbital hybridisations of oxygen atoms. The simulated oxygen K-edge fine
structures (ELNES) calculated with the TELNES program were compared with experimental results obtained by electron energy-loss
spectrometry (EELS), showing good agreement. We show that changes in the fine structures of the investigated vanadium oxides
mainly result from changes in the O-p DOS and not from the shift of the DOS according to a rigid band model.
Received 17 December 2001 / Received in final form 19 June 2002 Published online 13 August 2002 相似文献
16.
P. Zieliński W. Schranz D. Havlik A.V. Kityk 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):155-165
A four-state pseudospin model is constructed for the isomorphous phase transition hcp-2↦hcp-1 in pure C70 and in C70-rich mixed crystal C
70(1 - x)
C60x. With the specific anisotropic pseudospin interactions adapted to the C70 crystal the model is equivalent to a two-state Ising model in a temperature-dependent field. Replica symmetric state of the
model is shown to approach the critical point when the width of distribution of random fields and/or of random bonds increases.
The temperature of the phase transition and the phase equilibrium temperature then are practically constant, whereas the experiment
shows their strong decrease with x. The main effect of dilution resides in an x-dependence of the model parameters. Dilatometric data on the hexagonal C
70(1 - x)
C60x are used to fit these parameters. A metastable disordered phase subsisting below the phase transition is discovered in a
range of the model parameters and is shown to be responsible for the macroscopic behaviour of the system. A good agreement
with experimental data is obtained for the spontaneous strain and for the x-dependence of the hysteresis.
Received 20 April 2001 and Received in final form 26 September 2001 相似文献
17.
M. Pedio N. Mahne F. Borgatti S.K.M. Henze F.S. Tautz R. Hudej B. Nickel 《Applied Surface Science》2007,254(1):103-107
Thin films of pentacene (C22H14) have become widely used in the field of organic electronics. Here films of C22H14 of thickness ranging from submonolayer to multilayer were thermally deposited on Ag(1 1 1) surface. The determination of molecular geometry in pentacene films on Ag(1 1 1) studied by X-ray absorption at different stages of growth up to one monolayer is presented.XAS spectra at the C K-edge were collected as a function of the direction of the electric field at the surface. The different features of the spectra were assigned to resonances related to the various molecular unoccupied states by the comparison with the absorption coefficient of the pentacene gas phase. The transitions involving antibonding π states show a pronounced angular dependence for all the measured coverages, from submonolayer to multilayer. The spectra analysis indicates a nearly planar chemisorption of the first pentacene layer with a tilt angle of 10°. 相似文献
18.
Titanium dioxide (TiO2) films were fabricated by cosputtering titanium (Ti) target and SiO2 or Si slice with ion-beam-sputtering deposition (IBSD) technique and were postannealed at 450 °C for 6 h. The variations of oxygen bonding, which included high-binding-energy oxygen (HBO), bridging oxygen (BO), low-binding-energy oxygen (LBO), and three chemical states of titanium (Ti4+, Ti3+ and Ti2+) were analyzed by X-ray photoelectron spectroscopy (XPS). The enhancement of HBO and reduction of BO in O 1s spectra as functions of SiO2 or Si amount in cosputtered film imply the formation of Si-O-Ti linkage. Corresponding increase of Ti3+ in Ti 2p spectra further confirmed the property modification of the cosputtered film resulting from the variation of the chemical bonding. An observed correlation between the chemical structure and optical properties, refractive index and extinction coefficient, of the SiO2 or Si cosputtered films demonstrated that the change of chemical bonding in the film results in the modification of optical properties. Furthermore, it was found that the optical properties of the cosputtered films were strongly depended on the cosputtering targets. In case of the Si cosputtered films both the refractive indices and extinction coefficients were reduced after postannealing, however, the opposite trend was observed in SiO2 cosputtered films. 相似文献
19.
C. McGinley S. Al Moussalami M. Riedler M. Pflughoefft H. Borchert M. Haase A.R.B. de Castro H. Weller T. Möller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):225-228
We describe photoemission results from pure and Sb-doped SnO2 nanoparticles deposited on gold substrates. Photoelectron spectra with synchrotron radiation were recorded for Sn 3d, Sb
3d and O 1s core levels and valence bands in the 500-1200 eV energy range. For pure SnO2 nanoparticles the surface is terminated by an oxygen rich layer with no obvious surface environment for Sn. When doped n-type
with 9.1% or 16.7% Sb, dopant atoms are concentrated near the surface of the nanoparticles. The valence state of the dopant
atoms is predominantly SbV. Plasmon satellite features are also observed in core level photoemission spectra and their intensity relative to the main
peak increases with increasing photon energy.
Received 30 November 2000 相似文献
20.
D.K. Yu R.Q. Zhang S.T. Lee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(1):57-63
The structures and energetics of carbon bridged C60 clusters (C
60
)
n
Cm have been studied by simulated annealing technique within the tight-binding molecular-dynamics. The “sp2 addition” ball-and-chain dimers exhibit odd-even alternations over the number of chain atoms, with the dimers containing
even chain atoms more stable against dissociation than their immediate neighbors containing odd chain atoms. In addition to
the usual “sp2 addition” dimers, a pentagon-linked C121 isomer and a hexagon-linked C122 isomer are also found to be stable. Based on our tight-binding calculations, trimers and larger clusters can be simply regarded
as being made up of independent or weakly interacting dimers, if the C-C60 joints on a single cage are not too close to each other. Large C60 clusters connected by chains each containing only one or two carbon atoms have similar stability to that of constituent dimers,
indicating the possibility to form stable C60-carbon polymers.
Received 17 January 2001 and Received in final form 26 February 2001 相似文献