共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Suzuki N. Asai H. Kataura Y. Achiba 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):143-146
The formation of single-wall carbon nanotubes (SWNTs) by using laser vaporization technique in different ambient gas atmosphere
was investigated. SWNTs were prepared with Rh/Pd (1.2/1.2 atom%)-carbon composite rod in Ar and nitrogen gas atmosphere, respectively.
Raman spectra of raw carbon materials including SWNTs and photoluminescence mapping of dispersed SWNTs in a surfactant solution
demonstrate that the diameter distribution of SWNTs prepared in Ar atmosphere is narrower than those obtained by using CVD
technique (e.g. HiPco nanotube), even when the ambient temperature is as high as 1150 ○C. It was also found that nitrogen atmosphere gives wider diameter distribution of SWNTs than that obtained with Ar atmosphere.
Furthermore, the relative yield of fullerenes (obtained as byproducts) is investigated by using HPLC (high-performance liquid
chromatography) technique. It was found that the relative yield of higher fullerenes becomes lower, when nitrogen is used
as an ambient gas atmosphere. Based on these experimental findings, a plausible formation mechanism of SWNTs is discussed. 相似文献
2.
3.
M. Hedén M. Kjellberg A. V. Bulgakov K. Hansen E. E.B. Campbell 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):255-259
Molecular fusion is induced in clusters of fullerene molecules on excitation with fs laser pulses. The dependence of the mass
distributions of the fused products on the initial cluster distribution are studied and results for (C60)N and (C70)N clusters are compared. The fused products decay by emitting C2 molecules and the fragmentation spectrum is used to determine the initial excitation energy of the fused species. The threshold
excitation energy needed to induce fusion is consistent with the energetic thresholds for molecular fusion of fullerenes determined
previously in single collision experiments. 相似文献
4.
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
5.
R. S. Berry 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):5-6
We review some of the ways clusters offer special kinds
of insights both into properties of bulk matter and properties unique to
small systems. We then survey some of the tantalizing open questions that
lie ahead in cluster science. 相似文献
6.
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
7.
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
8.
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
9.
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
10.
D. Cheng S. Huang W. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(1):41-48
We have investigated segregation phenomena in Cu–Au
bimetallic clusters with decahedral structures at 100 K and 300 K, based on
the second-moment approximation of the tight-binding (TB-SMA) potentials by
using Monte Carlo method. The simulation results indicate that there are
three regions (split, three-shell onion-like and core-shell region) at 100 K
and two regions (split and core-shell) at 300 K with the structure of
decahedral clusters, as the chemical potential difference Δμ
changes. It is found that the structure of decahedral clusters undergoes a
division into smaller clusters in the split region. In the core-shell
structure, Au atoms are enriched in surface and Cu atoms occupy the core of
the clusters because of the different surface energy of Cu and Au. The Au
atoms are enriched in the surface shell, and the Cu atoms are in the middle
shell, while a single Au atom is located in the center to form the
three-shell onion-like structure. The structure and binding energy of
smaller clusters after splitting are also discussed. The Au atoms generally
lie on the surface of the smaller clusters after splitting. 相似文献
11.
R. Thissen P. Lablanquie R.I. Hall M. Ukai K. Ito 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):335-342
Photoionization of rare gas clusters in the innervalence shell region has been investigated using threshold photoelectron
and photoion spectrometers and synchrotron radiation. Two classes of states are found to play an important role: (A) valence
states, correlated to dissociation limits involving an ion with a hole in its innervalence ns shell, (B) Rydberg states correlated to dissociation limits involving an ion with a hole in its outervalence np shell plus an excited neutral atom. In dimers, class A states are “bright”, that is, accessible by photoionization, and serve
as an entrance step to form the class B “dark” states; this character fades as the size of the cluster increases. In the dimer,
the “Mulliken” valence state is found to present a shallow potential well housing a few vibrational levels; it is predissociated by the
class B Rydberg states. During the predissociation a remarkable energy transfer process is observed from the excited ion that
loses its innershell electron to its neutral partner.
Received: 10 February 1998 / Revised: 17 July 1998 / Accepted: 31 July 1998 相似文献
12.
13.
M. Neeb R. Klingeler P.S. Bechthold G. Kann I. Wirth S. Eisebitt W. Eberhardt 《Applied Physics A: Materials Science & Processing》2001,72(3):289-293
Mass spectra of fullerenes doped with transition and rare earth metals (Sc, Y, La, Ce, Gd) reveal a variety of singly and
doubly doped metallofullerenes. Characteristic oscillations of the relative mass intensities of the La- and Y-metallofullerenes
suggest the existence of two different isomers of the corresponding doubly doped fullerenes. The yield of the plasma-generated
clusters is sufficient to be used for an in situ deposition of mass-selected metallofullerenes onto a surface. In particular,
endohedral fullerenes with 60 or less atoms are accessible for deposition by means of a laser vaporization cluster source.
Scanning tunneling microscopy has been used to image Ce@C60 and La@C60 on highly oriented pyrolytic graphite.
Received: 24 May 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001 相似文献
14.
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
15.
R.-J. Tarento P. Joyes S. Benlamari R. Lahreche D. E. Mekki 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):237-240
We make a theoretical study of the shake-up of the 1s photoemission of C60. The method takes into account the N-body reactions of the π and σ electrons which appear
during the formation of the photoemission hole on one carbon atom. We analyze the origin of the satellite in the spectra due
to transitions between N-body states. Our calculation shows that the
satellite spectra is essentially given by N-body transitions which involve the creation of one or two electron-hole pairs.
The method has been applied also to C48N12. The situation is more
complex. The spectra of the two most stable species have been investigated. Moreover the influence on the spectra of the position
of the hole created on the carbon atom in C48N12
has been examined (all the carbon positions are not equivalent for some isomers). 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.
18.
Y. Dong M. Springborg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):15-18
The geometries and electronic properties of the most stable small
Aun clusters with n=2 to 20 are presented.
An intensive search for low-energy minima of Aun clusters was carried
through using a density-functional tight-binding method combined with genetic algorithms for an unbiased global structure
optimization. The structural and energetic properties of the small gold clusters are compared with those of planar Aun clusters with n=5 to 15. 相似文献
19.
V. Tevekeliyska Y. Dong M. Springborg V. G. Grigoryan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):19-22
In this work we present results from a theoretical study on the properties of sodium clusters. The structures of the global
total-energy minima have been
determined using two different methods. With the parameterized
density-functional tight-binding method (DFTB) combined with a genetic-algorithm we investigated the properties of NaN clusters with cluster size up to 20 atoms, and with our own Aufbau/Abbau algorithm together with the embedded-atom method (EAM) up to 60 atoms. The two sets of results from the
independent calculations are compared and a stability function is studied as function of the cluster size. Due to the electronic
effects included in the DFTB method and the packing effects included in the EAM we have obtained different global-minima structures
and different stability functions. 相似文献
20.
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