共查询到20条相似文献,搜索用时 15 毫秒
1.
K. Nagaya H. Murakami H. Iwayama Y. Ohmasa M. Yao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):69-72
The spectra of deep inner-core excited mixed rare-gas clusters were recorded by using electron ion coincidence (EICO) and
multi-hit momentum imaging (MHMI) techniques.
The EICO spectra for Ar99Kr1 clusters reveal that singly charged ions are emitted from the inner-core excited clusters in addition to the multiple charged
ions.
The dependence of the EICO spectra on photon energy and cluster size suggests that the holes created through vacancy cascade
on the krypton atoms are transferred to the surrounding atoms, and that the singly charged ions are the primary product of
the krypton photoabsorption.
Charge localization is suggested for the inner-core excited mixed rare-gas clusters from the analysis of the EICO peak width.
The MHMI measurements give us direct evidence for the strong charge migration from X-ray absorbing atoms to surrounding atoms.
The photon energy dependence of the PSD image for fragment ions suggests that the momentum of the fragment ions depends on
the number of charges generated by the vacancy cascade. 相似文献
2.
E. Fort F. Pradère A. De Martino H. Vach M. Châtelet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(1):79-84
We present two complementary techniques that provide detailed diagnostics of supersonic beams involving several species. First,
surface scattering, together with quadrupole mass spectrometer detection, yields the monomer percentage for each species within
the beam. Second, analyses of beam profiles for different masses after scattering by a buffer gas permit determination of
mixed cluster presence and, if any, of cluster sizes and compositions. The two techniques are applied to supersonic expansions
of an argon-nitrogen mixture. We discuss the results that provide new insight in binary nucleation processes.
Received: 6 October 1997 / Revised: 4 November 1997 / Accepted: 13 November 1997 相似文献
3.
K. Hashimoto M. Okamoto K. Takayanagi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):75-78
The stability of neutral, singly and multiply ionized silicon clusters, (N
= 2-7, M
= 0, , , ), has been investigated using an ab initio density functional method. We show that the fragmentation effect significantly affects the structure of mass-spectra of multiply
ionized silicon clusters. For clusters, the clusters with a large fragmentation energy are found to correspond to the high peaks at N = 4 and 6 in mass-spectra. For clusters, a peak at N = 5 in mass-spectra has been predicted to be especially high.
Received: 9 June 1997 / Revised: 8 January 1998 / Accepted: 25 February 1998 相似文献
4.
M.A. Gaveau M. Briant P.R. Fournier J.M. Mestdagh J.P. Visticot F. Calvo S. Baudrand F. Spiegelman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):153-161
Spectroscopic experiments have been performed, providing emission and excitation spectra of calcium atoms trapped on argon
clusters of average size 2 000. The two experimental spectra fall in the vicinity of the calcium resonance line 1P 1 → 1S0 at 422.9 nm. The excitation spectrum consists in two bands located on each side of the resonance line of the free calcium.
In addition, Monte Carlo calculations, coupled to Diatomics-In-Molecule potentials are employed to simulate the absorption
spectrum of a single calcium atom in the environment of a large argon cluster of average size 300. The theoretical absorption
spectrum confirms the existence of two bands, and shows that these bands are characteristic of a calcium atom located at the
surface of the argon cluster and correspond to the excited 4p orbital of calcium either perpendicular or parallel to the cluster surface. The precise comparison between the shape of the
absorption spectrum and that of the fluorescence excitation spectrum shows different intensity ratios. This could suggest
the existence of a non adiabatic energy transfer that quenches partly the fluorescence of trapped calcium. Another explanation,
although less likely, could be a substantial dependence of the calcium oscillator strength according to the alignment of the
calcium excited orbital with respect to the cluster surface. The emission spectrum always shows a band in the red of the resonance
line which is assigned to the emission of calcium remaining trapped on the cluster. When exciting the blue band of the excitation
spectrum, the emission spectrum shows a second, weak, component that is assigned to calcium atoms ejected from the argon clusters,
indicating a competition between ejection and solvation.
Received 7 May 2002 Published online 1st October 2002
RID="a"
ID="a"e-mail: jmm@drecam.saclay.cea.fr
RID="b"
ID="b"URA 2453 du CNRS
RID="c"
ID="c"UMR 5626 du CNRS 相似文献
5.
V. Boutou A.R. Allouche F. Spiegelmann J. Chevaleyre M. Aubert Frécon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):63-73
The geometrical structure of ground state Ban clusters (n
=2-14) has been predicted from various types of calculations including two ab initio approaches used for the smaller sizes namely HF+MP2(
n
=2-6), DFT (LSDA)(
n
=2-6, 9) and one model approach HF+pairwise dispersion used for all sizes investigated here. The lowest energy configurations
as well as some isomers have been investigated. The sizes n
=4, 7 and 13 are predicted to be the relatively more stable ones and they correspond to the three compact structures: the tetrahedron,
the pentagonal bipyramid and the icosahedron. The growth behavior from Ba7 to Ba13 appears to be characterized by the addition of atoms around a pentagonal bipyramid leading to the icosahedral structure of
Ba13 which is consistent with the observed size-distribution of barium clusters. Values for vertical ionization potentials calculated
for n
=2-5 at the CI level are seen to be in quite good agreement with recent measures.
Received: 14 May 1997 / Received in final form: 2 February 1998 / Accepted: 27 February 1998 相似文献
6.
H. Nagao K. Awazu S. Hayakawa K. Iwamoto M. Toyoda T. Ichihara 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):279-287
Various dissociation channels of silver bromide cluster ion
Ag2Br+ and silver cluster ion Ag3
+ were observed in
high-energy collisionally-activated dissociation (CAD) using a Cs target.
The fragment patterns of the high-energy CAD were compared with those of the
metastable dissociation and low-energy CAD. The difference in the fragment
patterns between the high-energy CAD and the other dissociation methods was
explained in terms of the internal energy distributions. The dissociation
mechanisms of neutral silver bromide cluster Ag2Br and silver cluster
Ag3 were also investigated by charge inversion mass spectrometry using
the Cs target. While the fragment ions AgBr- and Ag2
- were
dominantly observed in the charge inversion spectrum of Ag2Br+,
the undissociated ion Ag3
- was observed as a predominant peak in
the case of Ag3
+. The dissociation behavior of Ag2Br*
can be explained on the basis of the calculated thermochemical data.
Contrary to this, the predominant existence of the undissociated
Ag3
- cannot be explained by the reported thermochemical data. The
existence of undissociated Ag3
- suggests that the dissociation
barrier is higher than the internal energy of Ag3
*
(theoretical: 1.03 eV, experimental: 2.31 eV) estimated from the ionization
potentials of Ag3 and Cs. 相似文献
7.
8.
I. L. Garzón M. R. Beltrán G. González I. Guterrez-González K. Michaelian J. A. Reyes-Nava J. I. Rodrguez-Hernández 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):105-109
Theoretical and experimental information on the shape and
morphology of bare and passivated gold clusters is fundamental
to predict and understand their electronic, optical, and other
physical and chemical properties. An effective theoretical
approach to determine the lowest-energy configuration (global
minimum) and the structures of low energy isomers (local minima)
of clusters is to combine genetic algorithms and many-body
potentials (to perform global structural optimizations), and
first-principles density functional theory (to confirm the
stability and energy ordering of the local minima). The main
trend emerging from structural optimizations of bare Au clusters
in the size range of 12-212 atoms indicates that many
topologically interesting low-symmetry, disordered structures
exist with energy near or below the lowest-energy ordered
isomer. For example, chiral structures have been obtained as the
lowest-energy isomers of bare Au28 and
Au55 clusters, whereas in the size-range
of 75-212 atoms, defective Marks decahedral structures are
nearly degenerate in energy with the ordered symmetrical
isomers. For methylthiol-passivated gold nanoclusters
[Au28(SCH3)16
and
Au38(SCH3)24],
density functional structural relaxations have shown that the
ligands are not only playing the role of passivating molecules,
but their effect is strong enough to distort the metal cluster
structure. In this work, a theoretical approach to characterize
and quantify chirality in clusters, based on the Hausdorff
chirality measure, is described. After calculating the index of
chirality in bare and passivated gold clusters, it is found that
the thiol monolayer induces or increases the degree of chirality
of the metallic core. We also report simulated high-resolution
transmission electron microscopy (HRTEM) images which show that
defects in decahedral gold nanoclusters, with size between 1-2
nm, can be detected using currently available experimental HRTEM
techniques. 相似文献
9.
M.L. Gardel R. Vandenbosch B.P. Henry C. Cooper D.I. Will 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):79-81
The destruction cross-section for 22.5 and 50 keV C1- , for 10 and 50 keV C8
1- and for 50 and 75 keV C60
1- clusters in collisions with H2 has been measured by an attenuation method. The destruction of the cluster anions is dominated by electron detachment rather
than fragmentation and is of the order of the geometric cross-section. The cross-sections vary little with bombarding energy.
Received: 16 September 1998 / Received in final form: 23 February 1999 相似文献
10.
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
11.
C. Becker J. Gspann R. Krämer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):301-304
Reactive accelerated cluster erosion (RACE) of single crystal artificial diamond has been used to fabricate various nano-
and microstructures. Carbondioxide clusters of about 1000 molecules are accelerated to 100 keV to act as the eroding agent.
Using movable shadow masks, the accelerated cluster beam may erode staircase structures acting as an optical grating. A cycloid
gear has been generated via a stationary nickel mask. Non-reactive accelerated cluster erosion using argon clusters will be considered for comparison.
Received 30 November 2000 相似文献
12.
A. Glotov O. Knospe R. Schmidt E.E.B. Campbell 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):333-336
New experimental data is reported for the absolute cross sections for the fusion reaction channel in single gas-phase collisions
between fullerenes. The experimental data is compared with the results of quantum mechanical and classical molecular dynamics
simulations as well as with simple models. Quantum molecular dynamics simulations are in very good quantitative agreement
with the experimental data. The overall dynamical behaviour can be well-described qualitatively in the framework of simple
models.
Received 2 October 2000 相似文献
13.
E.E.B. Campbell K. Hoffmann I.V. Hertel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):345-348
The timescale for the coupling of electronic and vibrational excitation in isolated fullerenes is determined by recording
positive ion time-of-flight mass spectra on excitation with ultrashort laser pulses at 790 nm of the same fluence but different
pulse durations. The coupling leads to the onset of a delayed ionisation “tail” on the parent fullerene ion peak. This occurs
for a pulse duration of 500-1000 fs, depending on laser fluence.
Received 20 October 2000 相似文献
14.
F. Despa W. Bouwen F. Vanhoutte P. Lievens R.E. Silverans 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):403-411
The influence of doping of Li-clusters by electronegative O and C atoms on the ionization potentials was investigated. Experimentally,
we report ionization potentials for bare Lin clusters deduced from photoionization efficiency spectra. The values are compared with the results for LinO and LinC clusters. Observed differences are largely attributed to a quantum size effect caused by the segregated molecular part around
the impurity, which changes the electron work function. Theoretically, the Fermi and exchange-correlation energies which enter
the work function, are calculated in the frame of the augmented plane wave (APW) method by taking explicitly into account
the presence of the molecular core. The other contribution to the work function, the moment of the double layer at the cluster
surface, is computed by solving the corresponding Poisson's equation.
Received 9 September 1999 and Received in final form 7 February 2000 相似文献
15.
F.F. Karpeshin J. da Providência C. Providência J. da Providência Jr 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):319-326
Two types of extreme collective motion, large-amplitude many-phonon vibration of the ionic core and rotation of the cluster
with high angular momenta, are considered. The interplay between vibration and collective motion towards fission is discussed.
A new mechanism of formation and rupture of the neck is proposed which is based on the Franck-Condon principle, and accounts
for the interplay between vibration and fission. Under rotation, the change of the shape of the cluster and a phase transition
from axially symmetric to triaxial ellipsoid are predicted. For studying the effects, vibrational motion can be induced by
laser radiation. Rotational motion may arise in collisions of clusters.
Received 26 April 2001 and Received in final form 15 October 2001 相似文献
16.
H. Kitamura 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):33-36
Optimized structures and cohesive energies of small
mercury clusters (HgN; N = 3–7, 13, 19) are calculated with the
spin-orbit diatomics-in-molecules method. The theory takes into account the
effect of s-p mixing which tends to enhance the binding energies in the
ground state. It is shown that excimer clusters have significantly short
optimum bond lengths and their atomic geometries differ considerably from
those in the ground state. Excitation energy gap depends sensitively on both
cluster size and nearest-neighbor separation. Numerical results are compared
with other theories and experiments. 相似文献
17.
K. Hamada T. Wada C. Guet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):359-368
Stability of highly charged metal clusters in the electric field of an external ion is investigated with the classical liquid
drop model. We study the optimum shape of the cluster which has a local minimum of the total energy, taking account of the
effects of the surface charge polarization on the Coulomb energy and the cluster deformation on the surface energy. We find
that the cluster deformation greatly affects the total energy of the system and that a cluster with a fissility larger than
some critical value 0.7-0.8 can become unstable against deformation. We investigate the local competition between the Coulomb
force and the surface tension at the cluster surface and show that the surface charge polarization which is induced by the
external electric field significantly affects the shape of the cluster and its stability.
Received 5 November 2002 / Received in final form 27 January 2003 Published online 11 March 2003
RID="a"
ID="a"e-mail: hamada@konan-u.ac.jp 相似文献
18.
M. Vogel K. Hansen A. Herlert L. Schweikhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):163-166
The dimer dissociation energies of gold cluster ions Au
+
n
, n
= 9, 11, 13, 15 have been determined with an extension of a recently developed model-independent method. Monomer-dimer decay
pathway branching ratios provide the energy dependent process which is needed in this method. The measured values are D
2
(
Au
+
9
) = 3.66(8)(9) eV, D
2
(
Au
+
11
) = 4.27(11)(8) eV, D
2
(
Au
+
13
) = 4.50(9)(7) eV and D
2
(
Au
+
15
) = 4.29(10)(6) eV.
Received 13 May 2002 / Received in final form 22 July 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: manuel.vogel@uni-mainz.de 相似文献
19.
Systematic study of small BN clusters 总被引:2,自引:0,他引:2
S. Guerini P. Piquini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):17-20
We performed a systematic investigation of the small BxNy (x + y? 6) clusters using the ab initio Hartree-Fock scheme plus second-order perturbation theory. The nature of the potential energy surface extrema are analyzed
through analytical total energy second derivatives. Ionization potentials, binding energies and the stability against some
possible reaction mechanisms are calculated. Based on these results we propose that the growing process for these clusters
is mainly due to the successive incorporation of BN molecules. A discussion of some mass spectrometry experimental results
is also presented.
Received 2 October 2000 相似文献
20.
M. Vogel K. Hansen A. Herlert L. Schweikhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):73-76
The decay pathway competition between monomer and dimer evaporation of photoexcited cluster ions Au
+
n, n = 2-27, has been investigated by photodissociation of size-selected gold clusters stored in a Penning trap. For n > 6 the two decay pathways are distinguished by their experimental signature in time-resolved measurements of the dissociation.
For the smaller clusters, simple fragment spectra were used. As in the case of the other copper-group elements, even-numbered
gold cluster ions decay exclusively by monomer evaporation, irrespective of their size. For small odd-size gold clusters,
dimer evaporation is a competitive alternative, and the smaller the odd-sized clusters, the more likely they decay by dimer
evaporation. In this respect, Au
+
9 shows an anomalous behavior, as it is less likely to evaporate dimers than its two odd-numbered neighbors, Au
+
7 and Au
+
11. This nonamer anomaly is typical for copper-group cluster ions M
+
9 (M = Cu, Ag, Au) and a similar behavior is found in the anionic heptamers M
-
7. It is discussed in terms of the well-known electronic shell closing at n
e = 8 atomic valence electrons.
Received 2 November 2000 相似文献