共查询到20条相似文献,搜索用时 15 毫秒
1.
J.P. Santos P. Patte F. Parente P. Indelicato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(1):27-31
Using a laser-induced fluorescence method a detailed analysis of profiles of the 114Cd 326.1 nm line perturbed by argon 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 in the adiabatic approximation
for different interaction potentials.
Received 19 July 2000 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.
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
5.
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
6.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
7.
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
8.
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
9.
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
10.
R. Lefort A. Hédoux Y. Guinet E. Cochin M. Descamps 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):519-525
The first analysis of rapid intramolecular motions of triphenyl phosphite by 2H NMR is presented. The fragile slowing down of the primary relaxation is followed by a solid-echo method. The occurrence
of a fast reorientation of the phenyl side groups is demonstrated in the supercooled liquid state, identified as a two-fold
flip on the basis of simple lineshape simulations. Coexistence of both static and motionally averaged components in “two phase”
spectra indicate a broad distribution of correlation times for this relaxation. This dynamical behavior is shown to persist
in the glacial phase.
Received 28 May 2002 / Received in final form 1st October 2002
Published online 31 December 2002 相似文献
11.
G. Riou S. Jandl M. Poirier V. Nekvasil M. Diviš P. Fournier R.L. Greene D.I. Zhigunov S.N. Barilo 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(2):179-182
We present an infrared crystal-field study of Pr2CuO4 single crystals and thin films. Excitations from the ground state multiplet 3H4 to the 3H5, 3H6, 3F2 and 3F3 excited multiplets are observed in both single crystals and thin films. A precise set of crystal-field parameters, that reproduces
the energy and the symmetry of the levels, is determined.
Received 25 April 2001 相似文献
12.
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
13.
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
14.
Studying the ω<Emphasis Type="Italic">N</Emphasis> elastic and inelastic cross section with nucleons
Ye.S. Golubeva W. Cassing L.A. Kondratyuk A. Sibirtsev M. Büscher 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):271-277
We explore the possibility to measure the elastic and inelastic ωN cross section in p+d→d+ω+p
sp and p+A reactions. Our studies indicate that the elastic scattering cross sections can be determined for ω momenta above 1 GeV/c
in p+d reactions by gating on high proton spectator momenta whereas the ωN absorption cross section down to low relative ω momenta is most effectively studied in p+A reactions at beam energies 2.0–2.7 GeV.
Received: 15 October 1999 相似文献
15.
J.-H. Wu J.-Y. Gao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):315-319
In order to achieve the phase-sensitive probe gain without population inversion, we investigate a three-level Λ-type atomic system driven by a coherent field and a microwave field. It is shown that, by modulating the relative phase of
applied fields, we can obtain quite high inversionless gain at different probe detunings and change the gain behavior of the
probe correspondingly. We find that amplitudes of the coherent field and the microwave field are also important factors that
can result in different gain behavior of the probe. Here, we use the microwave field to induce the quantum coherence between
the two ground levels, which is necessary for phase-sensitive effects, since it can result in the interference between two
different transition channels.
Received 20 June 2002 / Received in final form 5 December 2002 Published online 4 March 2003 相似文献
16.
G. Modugno G. Roati M. Inguscio M.S. Santos G.D. Telles L.G. Marcassa V.S. Bagnato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):409-413
We report a comparative investigation of trap loss rates in a magneto-optical trap for two potassium isotopes, 39K and 40K, as a function of trap light intensity. The isotopes present a quite similar behavior for the loss rates at high intensities,
and a sudden increase of the loss rates at low intensities is present in both cases. While for 39K such increase can be explained assuming that the major contribution to the losses comes from hyperfine changing collisions,
a different loss mechanism must be considered for 40K, which has an inverted ground state hyperfine structure. The experimental results of both isotopes are well reproduced by
an alternative model based on radiative escape as the dominant loss mechanism.
Received 1st May 2002 / Received in final form 19 October 2002 Published online 4 March 2003
RID="a"
ID="a"Alternative address: Dipartimento di Fisica, Universitá di Trento, 38050 Povo (Tn), Italy.
RID="b"
ID="b"e-mail: marcassa@if.sc.usp.br 相似文献
17.
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
18.
D. Demir Y. Şahin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):17-22
The effect of an external magnetic field on the L3
subshell fluorescence yields (ω3 ) and level widths ($\Gamma_{L_3}$) for paramagnetic Ta, W, Tl, Th and U have been investigated using the
59.54 keV incident photon energy in the external magnetic field of
intensities ±0.60 T. L3 X-ray fluorescence cross sections ($\sigma_{L_3}^{X}$)
have been measured for the same elements. The measured ω
3, $\Gamma_{L_3} $
and $ \sigma_{L_3}^X$ values for B = 0 are in good
agreement with the theoretical values. It was observed that the values of
$\sigma_{L_3}^X$
and ω3 with the applied magnitude of the
magnetic field in both directions show a decreasing trend for paramagnetic
Ta, W, Tl, Th and U. Furthermore, in the presence of an external magnetic
field, the values of
$\Gamma_{L_3}$
show an increasing trend for
the same elements. The results show that the atomic parameters such as
spectral linewidth, radiation rates, photoionization cross section and
fluorescence yield can change when the irradiation is conducted in a
magnetic field. 相似文献
19.
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
20.
Amarjit Soni 《Pramana》2004,62(2):415-437
Status of lattice calculations of hadron matrix elements along with CP violation inB and inK systems is reviewed. Lattice has provided useful input which, in conjunction with experimental data, leads to the conclusion
that CP-odd phase in the CKM matrix plays the dominant role in the observed asymmetry inB → ψK
s. It is now quite likely that any beyond the SM, CP-odd, phase will cause only small deviations in B-physics. Search for the
effects of the new phase(s) will consequently require very large data samples as well as very precise theoretical predictions.
Clean determination ofall the angles of the unitarity triangle therefore becomes essential. In this regardB → KD0 processes play a unique role. RegardingK-decays, remarkable progress made by theory with regard to maintenance of chiral symmetry on the lattice is briefly discussed.
First application already provide quantitative information onB
K and the ΔI = 1/2 rule. In the lattice calculation, the enhancement in Re A0 appears to arise solely from tree operators, esp. Q2; penguin contribution toRe A0 appears to be very small. However, improved calculations are necessary for ε’/ε as the contributions of QCD penguins and
electroweak penguins largely seem to cancel. There are good reasons, though, to believe that these cancellations will not
survive improvements that are now underway. Importance of determining the unitarity triangle purely fromK-decays is also emphasized. 相似文献