共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
R.I. Eglitis E.A. Kotomin G. Borstel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):483-486
The origin of the intrinsic excitonic (“green”) luminescence in ABO3 perovskites remains a hot topic over the last quarter of a century. We suggest as a theoretical interpretation for the “green”
luminescence in these crystals, the recombination of electron and hole polarons forming a charge transfer vibronic exciton.
In order to check quantitatively the proposed model, we performed quantum chemical calculations using the Intermediate Neglect
of Differential Overlap (INDO) method combined with the periodic defect model. The luminescence energies calculated for four
perovskite crystals are found to be in good agreement with experimental data.
Received 19 December 2001 and Received in final form 14 March 2002 Published online 25 June 2002 相似文献
3.
V. O. Nesterenko W. Kleinig P. -G. Reinhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):57-64
Recent experimental data on the dipole plasmon in axial sodium clusters Na N + with 11 ≤ N ≤ 57 are analyzed within a self-consistent separable random-phase approximation (SRPA) based on the deformed Konh-Sham functional. Good agreement with the data is achieved. The calculations show that, while in light clusters plasmon properties (gross structure and width) are determined mainly by deformation splitting, in medium clusters with N τ 50 the Landau fragmentation becomes decisive. Moreover, in medium clusters shape isomers come to play with contributions to the plasmon comparable with the ground state one. As a result, commonly used methods of the experimental analysis of cluster deformation become useless and correct treatment of cluster shape requires microscopic calculations. 相似文献
4.
C. Yannouleas U. Landman A. Herlert L. Schweikhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):81-85
Using Penning-trap experiments and a shell-correction method incorporating ellipsoidal shape deformations, we investigate
the formation and stability patterns of trianionic gold clusters. Theory and experiment are in remarkable agreement concerning
appearance sizes and electronic shell effects. In contrast to multiply cationic clusters, decay of the trianionic gold clusters
occurs primarily via electron autodetachment and tunneling through a Coulomb barrier, rather than via fission.
Received 9 January 2001 相似文献
5.
A. Rytkönen M. Manninen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):351-357
The effect of melting transition on the ionization potential has been studied for sodium clusters with 40, 55, 142, and 147
atoms, using ab initio and classical molecular dynamics. Classical and ab initio simulations were performed to determine the ionization potential of Na142 and Na147 for solid, partly melted, and liquid structures. The results reveal no correlation between the vertical ionization potential
and the degree of surface disorder, melting, or the total energy of the cluster obtained with the ab initio method. However, in the case of 40 and 55 atom clusters, the ionization potential seems to decrease when the cluster melts.
Received 1st November 2002 Published online 24 April 2003
RID="a"
ID="a"e-mail: ar@phys.jyu.fi 相似文献
6.
W. Kleinig V.O. Nesterenko P.-G. Reinhard Ll. Serra 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):343-352
The systematics of the plasmon response in spherical K, Na and Li clusters in a wide size region is studied. Two simplifying approximations whose validity has been established previously are considered: (a) a separable
approach to the random-phase-approximation, involving an expansion of the residual interaction into a sum of separable terms,
(b) the electron-ion interaction is modeled within the pseudo-Hamiltonian jellium model (PHJM) including nonlocal effects
by means of realistic atomic pseudoHamiltonians. In cases where nonlocal effects turn out to be negligible, the Structure
Averaged Jellium Model (SAJM) has been used. The leading role of Landau damping in forming the plasmon width in medium and
large clusters is demonstrated. Good agreement with available experimental data is achieved for K, Na (using the SAJM) and
small Li clusters (invoking the PHJM). The trends for peak position and width are generally well reproduced, even up to details
of the Landau fragmentation in several clusters. Less good agreement, however, is found for large Li clusters. The possible
reasons of the discrepancy are discussed.
Received: 22 April 1998 / Accepted: 24 July 1998 相似文献
7.
E. Api naniz F. Plazaola J.S. Garitaonandia 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(2):167-177
Tight Binding Linear Muffin-Tin Orbital (TB-LMTO) electronic calculations are presented for the magnetic and structural properties
of ordered and disordered FeAl alloys. The total energy, bulk modulus, lattice parameter and magnetic moments of B2, D03 and
B32 ordered structures and A2 disordered structure were calculated for different compositions. The different structures are
obtained by varying the position of Fe and Al atoms in a BCC superstructure. In this way, we examine the order-disorder transition
that takes place in these alloys. Disordered alloys present both larger Fe magnetic moment and lattice parameter than ordered
ones. In this work comparison of the calculated quantities with available experimental results is provided and it can be concluded
that the results are in quantitative agreement with the experimental trends.
Received 7 May 2002 / Received in final form 20 September 2002 Published online 4 February 2003
RID="a"
ID="a"e-mail: eaf@we.lc.ehu.es 相似文献
8.
F. Fehrer P. M. Dinh M. Bär P.-G. Reinhard E. Suraud 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):447-458
We investigate the dynamical evolution of a Na8 cluster embedded in Ar matrices of various sizes from N=30 to 1048.
The system is excited by an intense short laser pulse leading to high
ionization stages.We analyze the subsequent highly non-linear motion of cluster and Ar environment in terms of trajectories,
shapes, and energy flow.
The most prominent effects are: temporary stabilization of high charge states for several ps, sudden stopping of the Coulomb
explosion of the embedded Na8
clusters associated with an extremely fast energy transfer to the Ar
matrix, fast distribution of energy throughout the Ar layers by a sound wave.
Other ionic-atomic transfer and relaxation processes proceed at slower
scale of few ps. The electron cloud is almost thermally decoupled
from ions and thermalizes far beyond the ps scale. 相似文献
9.
Yu.N. Ovchinnikov V.Z. Kresin 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):297-302
The relaxation of an electron excited to the high energy region, is accompanied by the creation of various excitations (plasmons,
quasi-particles, phonons). The stages of this many-body, non-stationary phenomenon (cascade) are described microscopically.
The electron distribution function n(ɛ, t) and characteristic times for the whole energy range, are calculated.
Received 7 February 2003 Published online 11 April 2003 相似文献
10.
P.-G. Reinhard E. Suraud 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):315-322
We use time-dependent density functional theory coupled to molecular dynamics for ionic motion to compute the spectra of ionic
vibrations in small Na clusters. Comparison with results from the distance dependent tight-binding approach shows good agreement
between these two very different methods. We discuss the evolution of the spectra with cluster size and charge and the impact
of ionic vibrations on the optical response.
Received 23 July 2001 / Received in final form 5 July 2002 Published online 8 October 2002
RID="a"
ID="a"e-mail: suraud@irsamc.ups-tlse.fr 相似文献
11.
C. Voisin D. Christofilos N. Del Fatti F. Vallée 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):139-144
Femtosecond excitation and relaxation of nonequilibrium electrons are investigated in silver clusters using a two color pump-probe
technique with resonant excitation of the surface plasmon resonance and off resonant probing. The excitation process is shown
to be identical to that in metal films, and permits creation of a strongly athermal single electron excitation in a time scale
shorter than the duration of the pulses (25-30 fs), in agreement with the free-electron absorption model. Following the time
evolution of the nonequilibrium distribution yields information on the internal energy redistribution dynamics of the conduction
electrons and of its modification by confinement in metal clusters.
Received 1st December 2000 相似文献
12.
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
13.
A. Heidenreich I. Last J. Jortner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):195-202
We present a theoretical and computational study of the properties and the
response of the nanoplasma and of outer ionization in Xen clusters (n =
55–2171, initial cluster radius R0 = 8.7–31.0 ?) driven by
ultraintense near-infrared laser fields (peak intensity IM = 1015–1020 Wcm-2, temporal pulse length τ= 10–100 fs, and frequency ν= 0.35 fs-1). The positively charged high-energy nanoplasma produced by inner ionization nearly follows the oscillations of
the fs laser pulse and can either be persistent (at lower intensities of IM = 1015–1016 Wcm-2 and/or for larger cluster sizes, where the electron energy distribution is nearly thermal) or transient (at higher intensities
of IM = 1018–1020 Wcm-2 and/or for smaller cluster sizes). The nanoplasma is depleted by outer ionization that was semiquantitatively described by
the cluster barrier suppression electrostatic model, which accounts for the cluster size, laser intensity and pulse length
dependence of the outer ionization yield. The electrostatic model was further utilized for estimates of the laser intensity
and pulse
width dependence of the border radius R0
(I) for the attainment of complete outer ionization at
,
while at R0 > R0
(I) a persistent nanoplasma prevails. R0
(I)
establishes an interrelationship between electron dynamics and nuclear Coulomb explosion dynamics in ultraintense
laser-cluster interactions. 相似文献
14.
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
15.
C. Bréchignac Ph. Cahuzac B. Concina J. Leygnier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):91-94
We have studied experimentally the collisional charge transfer between a neutral atom and a multicharged metal-atom cluster.
The charge transfer cross section measured for Na 31
+ + + Cs is in the range of 400 ?2. The time-of-flight mass analysis of the singly charged collision products demonstrates that an energy of about 0.5 eV is
deposited in the cluster fragment during the charge transfer collision. This effect can be interpreted as a charge transfer
to an excited state of the metal cluster. The measured cross section for Na 31
+ + + Cs is larger than the one for Na 31
+ + Cs collisions. This difference between these two systems is due to the existence, for the first one, of a Coulombic repulsion
term in the collision output channel.
Received 24 October 2000 相似文献
16.
S. Teuber T. Döppner T. Fennel J. Tiggesbäumker K.H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):59-63
The photoionization of metal clusters in intense femtosecond laser fields has been studied. In contrast to an experiment on
atoms, the interaction in this case leads to a very efficient and high charging of the particle where tens of electrons per
atom are ejected from the cluster. The recoil energy distribution of the atomic fragment ions was measured which in the case
of lead clusters exceeds 180 keV. Enhanced charging efficiency which we observed earlier for specific pulse conditions is
not reflected in the recoil energy spectra. Both the average and the maximum energies decrease with increasing laser pulse
width. This is in good agreement with molecular dynamics calculations.
Received 20 December 2000 相似文献
17.
H. Portales L. Saviot E. Duval M. Gaudry E. Cottancin J. Lermé M. Pellarin M. Broyer B. Prével M. Treilleux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):197-200
Low-frequency Raman scattering experiments have been performed on thin films consisting of pure gold or gold-silver alloy
clusters embedded in alumina matrix. It is clearly shown that the quadrupolar vibrational modes are observed by Raman scattering
because of the effect of resonance with the excitation of the electronic surface dipolar plasmon. This is due to the strong
coupling between the collective electronic dipolar excitation and the quadrupolar vibrational modes. This effect of resonance
does not exist with the core electron excitations. The mixing of the conduction electron dipolar excitation (surface plasmon)
with the core electrons leads to the quenching of the resonant Raman scattering.
Received 16 November 2000 相似文献
18.
19.
Metallic evolution of small magnesium clusters 总被引:1,自引:0,他引:1
J. Akola K. Rytkönen M. Manninen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):21-24
Structural and electronic properties of small magnesium clusters (N≤13) are studied using a first-principles simulation method in conjunction with the density functional theory and generalized
gradient correction approximation for the exchange-correlation energy functional. It is observed that the onset of metallization
of magnesium clusters is hard to assign since both the s-p hybridization and the energy gap between the valence and conduction bands do not evolve rapidly towards the known bulk properties.
Instead these quantities show a slow and nonmonotonic evolution.
Received 15 November 2000 相似文献
20.
P. Farmanara H.-H. Ritze V. Stert W. Radloff I.V. Hertel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):193-209
Neutral ammonia clusters (NH3)m are photo-excited to the electronic state by a deep UV femtosecond laser pump pulse. Within a few hundred femtoseconds a significant fraction of the clusters
rearrange to form an H-transfer state (NH3)m-2NH4(3s)NH2 with the subunit NH4 in its 3s electronic ground state. This state is then electronically excited by a time-delayed infrared control pulse of variable wavelength.
Finally, a third (probe) pulse in the UV ionizes the clusters for detection. The lifetime of the excited (NH3)m-2NH4(3p)NH2 states is found to vary between 2.7 and 0.13 ps depending on cluster size and excitation energy. It increases drastically
upon deuteration. The corresponding cluster size-dependent photoelectron spectra allow us to disentangle the underlying energetics
of the excitation and ionization process and reveal additional processes, such as nonresonant ionization or dissociative ionization.
The experimental findings suggest that the excited H-transfer ammonia complexes with m > 2 are deactivated by an internal conversion process back to the electronically lowest H-transfer state followed by fast
dissociation.
Received 22 September 2001 and Received in final form 31 January 2002 相似文献