共查询到20条相似文献,搜索用时 9 毫秒
1.
N. Hori A. Furuya M. Tsuruta F. Misaizu K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):41-44
Photoinduced dissociation in the ultraviolet region has been investigated for Ag nF n-1
+ cluster ions. Photodissociation spectrum of
Ag2F+
in the energy of 3.8–5.6 eV exhibits several sharp bands corresponding to the transition to electronically excited states.
In this dissociation, only the Ag2
+ ion was observed as a fragment ion. Theoretical calculation indicates that the parent Ag2F+ ion has a linear Ag-F-Ag equilibrium geometries in the ground and excited states. Since conformational changes by excitation
of bending vibration are necessary for the fragmentation of an F atom, this indicates that production of Ag2
+ from Ag2F+ is a result of internal conversion and following conformational changes. 相似文献
2.
M. B. Torres L. C. Balbás 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):217-220
We present a first-principles pseudopotential optimization of
the lower energy equilibrium structure of SinSc- anions for
n=14-18. We find that Si16Sc- is more stable than its
neighbors clusters, in agreement with recent experimental mass spectra. We
also optimize the geometry of pure Sin neutral clusters in the range
n=14-18, and compare our results with those from previous
first-principles calculations. 相似文献
3.
M. Bertolus V. Brenner P. Millié 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):387-394
An ab initio study of the Nan(OH)n, Nan(OH)n-1
+, Agn(OH)n, and Agn(OH)n-1
+ clusters with n up to four is presented. The results of this study show that, in accordance with experimental observations, the sodium hydroxide
clusters are almost purely ionic, while the Ag-O bond exhibits a significant covalent character. The perturbation caused by
the non-spherical OH- group relatively to an atomic anion, as well as the influence on structures and energies of the covalent character of the
metal-oxygen bond are determined. The appearance of metal-metal bonds in the silver hydroxide clusters is also discussed.
Finally, the theoretical results obtained on the Na-OH clusters are compared to experimental results available on the dissociation
of the Nan(OH)n-1
+ clusters.
Received 9 August 1999 and Received in final form 1st December 1999 相似文献
4.
S. Neukermans N. Veldeman E. Janssens P. Lievens Z. Chen P.v.R. Schleyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):301-308
We report a combined experimental and computational
investigation of small AlnOm species (n ≤20, m ≤
12), produced in a laser vaporization cluster source. The oxygen
content in the clusters was tuned by varying the oxygen
concentration in the carrier gas. Ionization energies are
bracketed using different ionizing photon energies in the energy
range between 5.37 and 7.89 eV. Among the singly doped AlnO
species, Al3O and Al15O are found to have relatively low
ionization energies, which can be related to the magic character
of the corresponding cations. Peculiarly low ionization energies
also are observed for specific oxygen rich species (m > 1),
suggesting the formation of ionically bound subunits. The
structures and ionization energies of singly doped AlnO0,+
(n = 1 - 7) clusters were determined using density functional
theory (B3LYP/6-311+G(d)).
Electronic supplementary material Supplementary Online Material 相似文献
5.
Structural and electronic properties of Bin (n = 2-14) clusters from density-functional calculations
J. M. Jia G. B. Chen D. N. Shi B. L. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):359-365
The structural and electronic properties of Bin
(n = 2-14) clusters have been systematically studied using gradient-corrected
density-functional theory. For each cluster size, a number of structural
isomers were constructed and optimized to search for the lowest-energy
structure. The competition of several structural patterns such as cages,
superclusters, and layered structures leads to the alternating appearance of
these configurations as global minima. Although the tendency of Bi to form
puckered-layer structures is already well-known, the electronic states of
Bin clusters are still far from that of the bulk. As well, a remarkable
even-odd atom number oscillation is observed in the structural and
electronic properties of the clusters, implying that the stability of
Bin clusters is mainly dominated by the electron shell effect rather
than by geometrical packing. The theoretically calculated values for
electron affinities agree well with available experimental data. 相似文献
6.
J. Akola A. Rytkönen H. Häkkinen M. Manninen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):93-99
The ionization potential of sodium clusters () at a finite temperature is studied using density functional theory and ab initio molecular dynamics. The threshold regions of the photoionization efficiency curves are deduced from the integrated IP distributions,
which are obtained from the energy eigenvalues of the highest occupied Kohn-Sham states during molecular dynamics by applying
a theoretically well-defined shift. The calculated ionization potentials are directly compared to the experimental values.
The energetically best geometry of Na55 is found to be a slightly distorted icosahedron.
Received 16 April 1999 and Received in final form 6 July 1999 相似文献
7.
F.O. Talbot J.P. Simons 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):389-398
Mass-resolved resonant two photon ionisation (R2PI) and infrared ion dip spectra have been recorded for 4-phenylimidazole
(4PI) and its singly and multiply hydrated clusters 4PI(H2O)n = 0 - 4, under supersonic expansion conditions. In the case of 4PI(H2O)0,1, it has also been possible to record infrared spectra in both the ground (S0) and excited (S1) states. Combining the experimental data with the results of ab initio calculations has led to the structural assignment of each cluster. In each case, the water molecules bind primarily to the
NH site of the imidazole ring. Clusters with n≥ 2 incorporate linear water chains, in which the proton donating terminus bridges either to the π-electron system (n = 2) or to the >N: atom site (n = 3, 4) on the imidazole ring. Despite the creation of a “water wire”, connecting the donor and acceptor sites of imidazole,
there is no evidence of proton transfer in either the ground or excited state.
Received 20 December 2001 Published online 13 September 2002 相似文献
8.
K. Ohshimo F. Misaizu K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):339-342
Cluster anions of a sodium atom with acrylonitrile
molecules,
(n = 0–6), have been studied by
negative-ion photoelectron spectroscopy. In addition,
theoretical calculations by using density functional theory have
been performed to obtain optimized structures and vertical
detachment energies. For Na(AN)–, the
spectrum can be explained by excitation of two different isomers
of the anion. For
, a broad band is found in the
photoelectron spectrum, whose profile is almost identical with
those of previously reported photoelectron spectra of
and a negative ion of chemically
synthesized 1,3,5-cyclohexanetricarbonitrile (CHTCN) molecule.
From this resemblance of band profiles, we conclude that
oligomerization of (AN)3 takes place in
and the CHTCN is formed as the
intracluster reaction product. 相似文献
9.
N. Nishi K. Kosugi K. Hino T. Yokoyama 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):97-100
A new type of Co-C nanoparticles is synthesized from
CH2Cl2 solution of
Co4(CO)1
2 by heating up to 210
°C in a closed vessel. Transmission
electron microscope (TEM) and electron energy loss spectroscopy
(EELS) observation show that the particles are embedded in
amorphous carbon and their average size is 12 nm. The radial
structure function obtained from the extended X-ray absorption
fine structure (EXAFS) of the Co K-edge absorption of the Co-C
nanoparticles provides a Co-C average distance of 2.08 Å and the
Co-Co distances of 3.18 Å and 3.9 (±0.2) Å. The particles
exhibit the magnetic hysteresis curve with a coercive force of
200 Oe at 20 K and 260 Oe at 300 K. The temperature dependence
of the magnetic susceptibility measured under zero-field cooling
and 10 Oe field cooling conditions exhibits the behavior
characteristic of a set of single magnetic domain nanomagnets in
an amorphous carbon matrix. 相似文献
10.
A. Herlert L. Schweikhard M. Vogel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):65-68
Singly charged silver-cluster anions are produced in a laser vaporization source and transferred into a Penning trap. After
size selection the clusters are subjected to an electron bath in the trap, which results in the attachment of further electrons.
The relative abundance of dianions or trianions as a function of the clusters' size is analyzed by time-of-flight mass spectrometry.
Silver-cluster dianions are observed for sizes n≥ 24 and trianions for n > 100. In addition, a detailed study of the cluster sizes 24 ?n? 60 shows a pronounced resistance to electron attachment for singly charged anions Agn
- with a closed electronic shell, in particular Ag29
-, Ag33
-, and Ag39
-. Both the threshold size for the observation of dianionic silver clusters and the shell effects in the production yield correlate
favorably with previous theoretical investigations of the respective electron affinities.
Received 24 November 2000 相似文献
11.
J. Zhao Y. Luo G. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):309-316
Tight-binding model is developed to study the structural and electronic properties of silver clusters. The ground state structures
of Ag clusters up to 21 atoms are optimized by molecular dynamics-based genetic algorithm. The results on small Agn clusters (n = 3-9) are comparable to ab initio calculations. The size dependence of electronic properties such as density of states, s-d band separation, HOMO-LUMO gap, and ionization potentials are discussed. Magic number behavior at Ag2, Ag8, Ag14, Ag18, Ag20 is obtained, in agreement with the prediction of electronic ellipsoid shell model. We suggest that both the electronic and
geometrical effect play significant role in the coinage metal clusters.
Received 7 August 2000 相似文献
12.
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
13.
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
14.
A. C. Reber S. N. Khanna J. S. Hunjan M. R. Beltran 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):221-224
Theoretical electronic structure studies on (ZnO)n (n= 2–18, 21) have
been carried out to show that the transition from an elementary ZnO molecule
to the bulk wurtzite ZnO proceeds via hollow rings, towers, and cages. Our
first principles electronic structure calculations carried out within a
gradient corrected density functional framework show that small
ZnnOn (n=2–7) clusters form single, highly stable rings.
Zn3O3 and the symmetric cage Zn12O12 are shown to be
particularly stable clusters. Among larger clusters, the most stable are
oblong cages, Zn15O15, Zn18O18, and Zn21O21,
which are reminiscent of nanotubes. 相似文献
15.
16.
G. Martinet M. Chabot K. Wohrer S. Della Negra D. Gardès J. A. Scarpaci P. Désesquelles V. Lima S. Díaz-Tendero M. Alcamí P.-A. Hervieux M. F. Politis J. Hanssen F. Martín 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):149-152
We report on experimental and theoretical efforts designed
to understand the fragmentation of small carbon clusters.
Experimentally, a new detection system for high velocity
fragments has been recently developed allowing the fragmentation
of high velocity clusters to be totally recorded [1]. Results
for the branching ratios of deexcitation of
C5 and C9 formed
by electron capture in high velocity
collisions are presented. Theoretically, the dissociation
dynamics of C5 has been investigated
using a kinematical model based on the statistical theory of
Weisskopf. In this model various structural quantities
(geometries, dissociation energies, harmonic frequencies), are
required for both the parent cluster and the fragments. They
have been calculated within DFT and coupled-cluster formalisms
for Cn up to n = 9.
In all cases, a strong correlation between measured branching
ratios and calculated dissociation energies is observed. 相似文献
17.
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
18.
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
19.
20.
Ajeeta Dhavale D.G. Kanhere C. Majumder G.P. Das 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(4):495-500
The ground-state geometries, energetics and the stability of
(
n
=1-12) clusters are studied using ab initio molecular dynamics method. Our results indicate that the ground-state geometries of large clusters () are different from those of clusters where a trivalent impurity Al is added to the same monovalent host Na. Other features observed are an early appearance
of 3-dimensional structure and a pentagonal growth path from n
=6 up to n
=11. As expected, the ground-state geometry of is not an icosahedron but can be viewed as a distorted form of one of the low lying geometries of cluster. In the energetically favored structures impurity atom Mg is never located at the center of the cluster. The stability
analysis based on the energetics shows (8 valence electrons) to be the most stable. In addition there is a remarkable even-odd pattern observed in the dissociation
energy and the second difference in energy which is absent in earlier studies of and clusters.
Received: 16 September 1998 / Received in final form: 15 February 1999 相似文献