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1.
The processes of cluster formation in liquid alcohols, water, methanol, n-hexanol, and n-hexane have been investigated by the method of flicker-noise spectroscopy. Two types of clusters — clusters with a close-packed
structure and clusters with a loose structure — have been detected. The energy of formation of different clusters in methanol
and n-hexane ranges, respectively, from −250 to +250 J/mole and from −50 to +50 J/mole. The smallest clusters of methanol, n-hexanol, water, and n-hexane consist, respectively, of six, two, eleven, and two molecules, and their largest clusters represent oscillators consisting,
respectively, of 50,400, 17,200, 93,500, and 33,150 molecules at 274 K. In methanol at 271 K, more than 44 types of clusters
consisting of 6, 97, 152, 219, 297, 492, 1029, 1368, 1560, etc. molecules were detected. In n-hexanol at 273 K, 57 types of clusters were detected. Models of small clusters are proposed. In water, the content of close-packed
clusters is maximum at 277 K. The energy of formation/decomposition of small clusters in water ranges from −0.4 to +0.4 kJ/mole
and increases with increase in the water temperature. The hysteresis of transformation of the (H2O)280 cluster in the process of heating and cooling of water in the temperature range 273–280 K was detected. Series of energy
spectra of clusters in liquids at different temperatures are presented and discussed.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 305–312, May–June, 2005. 相似文献
2.
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
3.
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
4.
A systematic study on the geometrical structures, electronic and magnetic properties of Au5H
n
(n=1–10) clusters has been performed by using the all-electron scalar relativistic density functional theory with generalized
gradient approximation at the PW91 level. It is found that all Au5H
n
clusters prefer to keep the planar structures like pure Au5 cluster, the Au5 structures in Au5H4, Au5H5 and Au5H6 clusters are distorted obviously. The adsorption of a number of hydrogen atoms enhances the stability of Au5 cluster and all Au5H
n
clusters are more stable than pure Au5 cluster energetically. The odd-even alteration of magnetic moment is observed in Au5H
n
clusters and may be served as the material with tunable code capacity of “0” and “1” by adsorbing odd or even number of H
atoms. It seems that the most favorable adsorption between Au5 cluster and a number of hydrogen atoms takes place in the case that the odd number of hydrogen atoms is adsorbed onto Au5 cluster and becomes Au5H
n
cluster with even number of valence electrons. 相似文献
5.
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
6.
B. Kalita R. C. Deka 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):51-58
Density functional calculations have been performed to investigate CO adsorption on neutral, cationic and anionic Pdn (n=1–7) clusters. From the results, it is observed that the binding of CO molecule to neutral and cationic palladium clusters
takes place via 1-, 2- and 3-fold coordination. On the other hand, only terminal adsorption of CO molecule is possible in
anionic clusters barring bridging adsorption in Pd7
- cluster. 相似文献
7.
S. V. Makaev T. M. Bitokhov K. G. Kravchuk M. A. Urusova V. M. Valyashko 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(7):1045-1055
A flow hydrothermal setup with a tubular reactor equipped with a plunger pump and back pressure valves is used to study the
effects of scaling in the K2SO4-KCl-H2O, K2SO4-K2CO3-H2O, and Na2SO4-NaCl-H2O systems at pressures of up to 270–340 kg/cm2, temperatures of 400–600°C, and flow rates of 5.0 and 2.5 ml/min in order to establish conditions for the formation of salt
plugs of type 2 (K2SO4, Na2SO4) in the flow mode at supercritical (SC) state parameters and to explore ways of eliminating such salt deposits by means of
hydrothermal solvents, more specifically, high-temperature aqueous solutions of salts of type 1 (KCl, K2CO3, and NaCl). The concentrations of hydrothermal solvents sufficient to prevent the plugging of flow systems with solutions
containing 0.26–0.27 mol % K2SO4 or Na2SO4 are determined, and the effects of the flow rate and chemical composition of type 1 salts on this process are studied. The
results show that the phenomenon of scaling with the formation of salt plugs, which hinders the practical use of supercritical
water oxidation technology, can be eliminated by adding readily soluble electrolytes, salts of type 1, to initial aqueous
solution of type 2 salts. 相似文献
8.
T. Ritschel Ch. Zuhrt L. Zülicke P. J. Kuntz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):127-141
ArnHCl+ van-der-Waals clusters for n = 1–13 are investigated
with the “minimal diatomics-in-molecules (DIM) model”
using ab-initio input data obtained from multi-reference
configuration-interaction calculations plus subsequent projection onto
valence-bond wavefunctions.
The results for the complexes with n = 1–3 are checked against
ab-initio calculations at the
coupled-cluster (CCSD) level with the same one-electron atomic basis set as
for the input data generation (aug-cc-pVTZ from Dunning).
In addition to the electronic ground state,
the first excited
state for the triatomic
complex (n = 1) is also studied.
The results
from the DIM model are shown to be in fair agreement with those from
advanced conventional ab-initio calculations, although there are
differences in detail. The comparison
justifies the extension of the DIM approach to n > 3.
Systematic analysis of the local minima of the multi-dimensional
potential-energy surfaces (PESs), carried out with the combined
method
described in part I (Monte-Carlo sampling plus subsequent steepest-descent
optimization), reveals simple building-up regularities for the most
stable structures (i.e. those corresponding to the global PES minimum)
at each n: apart from always having a nearly linear
(Ar–H–Cl)+ fragment as core, the aggregates show little
or no symmetry. Secondary local minima are also determined and their
structures interpreted.
The PESs for the low-lying excited states reveal a much more complicated
topography compared to the ArnH+ clusters allowing a variety
of photo-processes.
The energy level sequence of the first five excited electronic states
and the stability of the clusters in these states is studied
as a function of the cluster size n. 相似文献
9.
X. J. Kuang X. Q. Wang G. B. Liu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(1):71-80
An all-electron scalar relativistic calculation on
Au
n
NO (n = 1–10) clusters has been performed by using density functional
theory with the generalized gradient approximation at the PW91 level. The
small gold cluster would like to bond with nitric and the nitric monoxide
molecule prefers to occupy the on-top and single fold coordination site. The
Au
n
structures in all Au
n
NO clusters are only distorted slightly
and still keep the planar structures. With the bend of Au-N-O bond, the
structures of Au
n
NO clusters evolve from the 2D structure to 3D
structure. The most favorable adsorption between small gold cluster and
nitric monoxide molecule takes place in the case that nitric monoxide
molecule is adsorbed onto an odd-numbered pure Au
n
cluster and becomes
odd-numbered Au
n
NO cluster with even number of valence electrons. The
scalar relativistic effect strengthens the Au–Au, Au–N interaction and
weakens the N–O interaction, appearing as the shorter Au–Au, Au–N
bond-length and the longer N–O bond-length. The differences between our work
and previous work are believed to be the reflection of the scalar
relativistic effect. 相似文献
10.
为了说明钡助剂的存在形式, 本文采用第一性原理方法研究了BaxOy小团簇修饰Ru(0001)表面的结构稳定性和氮分子吸附性质. 基于总能的热力学分析发现, 在实验条件下(500 K, PH2O/PH2<10-3), Ba2O团簇比BaO2, BaO, Ba和O等团簇(原子)更加稳定. 这证实含有金属性钡原子的团簇也是氧化钡助剂可能的工作状态. 表面电荷差分密度说明Ba2O团簇的氧和钡原子与衬底的作用不同. 不过Ba2O团簇氧和钡原子附近的氮分子吸附行为相似, Ba2O团簇增强了氮分子和衬底的相互作用. Ba2O团簇氧和钡原子附近的氮分子吸附能分别为0.78 和0.88 eV, 均大于清洁表面的0.67 eV. 氮分子间距和氮分子的拉伸振动频率都表明Ba2O团簇在一定程度上活化了吸附氮分子. Ba2O团簇氧和钡原子附近的N–N键长分别为0.117和0.116 nm, 大于清洁表面的0.114 nm. 氧和钡原子附近氮分子的拉伸振动频率分别为 1888 和1985 cm-1, 小于清洁表面的2193 cm-1. 电荷差分密度的计算结果说明, 削弱作用主要来自于Ba2O团簇中钡离子和氮分子间的静电作用. 两者间的静电作用增加了氮分子π 反键轨道的占据数, 促进了氮分子极化, 从而削弱氮分子键. 相似文献
11.
Absolute cross sections σ−(E, N) of electron attachment to clusters (H2O)
N
, (N2O)
N
, and (N2)
N
for varying electron energy E and cluster size N are measured by using crossed electron and cluster beams in a vacuum. Continua of σ−(E) are found that correlate well with the functions of electron impact excitation of molecules’ internal degrees of freedom.
The electron is attached through its solvation in a cluster. In the formation of (H2O)
N
−
, (N2O)
N
−
, and (N2)
N
−
, the curves σ−(N) have a well-defined threshold because of a rise in the electron thermalization and solvation probability with N. For (H2O)900, (N2O)350, and (N2)260 clusters at E = 0.2 eV, the energy losses by the slow electron in the cluster are estimated as 3.0 × 107, 2.7 × 107, and 6.0 × 105 eV/m, respectively. It is found that the growth of σ− with N is the fastest for (H2O)
N
and (N2)
N
clusters at E → 0 as a result of polarization capture of the s-electron. Specifically, at E = 0.1 eV and N = 260, σ− = 3.0 × 10−13 cm2 for H2O clusters, 8.0 × 10−14 cm2 for N2O clusters, and 1.4 × 10−15 cm2 for N2 clusters; at E = 11 eV, σ− = 9.0 × 10−16 cm2 for (H2O)200 clusters, 2.4 × 10−14 cm2 for (N2O)350 clusters, and 5.0 × 10−17 cm2 for (N2)260 clusters; finally, at E = 30 eV, σ− = 3.6 × 10−17 cm2 for (N2O)10 clusters and 3.0 × 10−17 cm2 for (N2)125 clusters.
Original Russian Text ? A.A. Vostrikov, D.Yu. Dubov, 2006, published in Zhurnal Tekhnicheskoĭ Fiziki, 2006, Vol. 76, No. 12,
pp. 1–15. 相似文献
12.
Ling Guo 《Journal of nanoparticle research》2011,13(5):2029-2039
The chemisorptions of hydrogen on aluminum arsenide clusters are studied with density functional theory (DFT). The on-top
site is identified to be the most favorable chemisorptions site for hydrogen. And the Al-top site is the preferred one in
the most cases for one hydrogen adsorption in (AlAs)
n
(n = 2, 5, 6, 8–15) clusters. Top on the neighboring Al and As atoms ground-state structures are found for two hydrogen adsorption
on (AlAs)
n
except for (AlAs)2 cluster. The Al–As bond lengths decrease generally as the size of the cluster increases. And there is a slight increase in
the mean Al–As bond lengths after H adsorption on the lowest-energy sites of the most AlAs clusters. In general, the binding
energy of H and 2H are both found to decrease with an increase in the cluster size. And the result shows that large binding
energies (BE) of a single hydrogen atom on small AlAs clusters and large highest occupied and lowest unoccupied molecular-orbital
gaps for (AlAs)H and (AlAs)3H make these species behaving like magic clusters. Calculations on two hydrogen atoms on (AlAs)
n
clusters show large BE for (AlAs)
n
H2 with an odd number of n. The stability of these complexes is further studied from the fragmentation energies. (AlAs)7H2 and (AlAs)9H2 clusters are again suggested to be the stable clusters. On the other hand both the fragmentation energy and the binding energy
for (AlAs)13H are close to the lowest values. 相似文献
13.
The presented work investigates the differences in magnetic properties of free and supported clusters via ab-initio calculations.
The electronic structure of the clusters was calculated using a spin polarized relativistic multiple-scattering Green’s function
formalism. We focus on Fe clusters of 2–9 atoms, either free or supported by Ni(001), and on Co clusters of 2–7 atoms, either
free or supported by Au(111). For the supported clusters, the spin and orbital magnetic moments depend on the cluster size
nearly monotonically, while for the free clusters large quasi-oscillations of magnetic moments with the cluster size were
observed. Similarly, for supported clusters, the local spin magnetic moments decrease nearly linearly with increasing coordination
number, while for free clusters of the same size range the trend is much more complicated. These findings are consistent with
the fact that the spectral distribution function contains much sharper features for free clusters than for supported clusters.
相似文献
14.
S. J. Candau P. Hebraud V. Schmitt F. Lequeux F. Kern R. Zana 《Il Nuovo Cimento D》1994,16(9):1401-1410
Summary Both linear and non-linear viscoelasticity experiments have been performed in semi-dilute micellar aqueous solutions of ethanediyl-α,ω-bis
(dodecylmethylammonium bromide) as a function of solution chloride (NaCl) concentration. The results suggest that both linear
and non-linear properties are affected by the electrostatic interactions. In particular, the plateau modulusG′∞ and the ratioσ
m/G′∞, whereσ
m represents the plateau value in a stress-shear rate experiment, are enhanced as the electrostatic interactions are screened
by addition of salt. The zero-shear viscosity is lowered upon addition of NaCl, due likely to an exchange of the Cl− ions with the Br− counterions.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
15.
C. Bréchignac Ph. Cahuzac B. Concina J. Leygnier I. Tignères 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):185-192
The cross-sections for collisional charge transfer between singly charged free clusters M
n
+ (M = Li, Na; n=1...50) and atomic targets A (cesium, potassium) have been measured as a function of collisional relative velocity in laboratory
energy range 1–10 keV. For each cluster size, the experimental values of the charge transfer cross-section are fitted with an universal parametric curve with two independent parameters and vm, the maximum cross-section and the corresponding velocity. For small size clusters (), the characteristic parameters show strong variations with the number of atoms in the cluster. Abrupt dips observed for n=10 and n=22 are attributed to electronic properties. Charge transfer patterns observed for various collisional systems present similarities,
which appear more sensitive to cluster quantum size effects than to collision energy defects. In their whole, the and vm parameters show differences in both their size evolution and their absolute values discussed in term of projectile and target
electronic structures.
Received 13 April 2000 and Received in final form 29 June 2000 相似文献
16.
T. Iino K. Ohashi K. Inoue K. Judai N. Nishi H. Sekiya 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):37-40
Vibrational spectra of mass-selected
Ag+(H2O)n ions are measured by infrared photodissociation
spectroscopy and analyzed with the aid of density functional theory
calculations. Hydrogen bonding between H2O molecules is found to be
absent for cold Ag+(H2O)3, but detected for
Ag+(H2O)4 through characteristic changes in the position and
intensity of OH-stretching transitions. The third H2O coordinates
directly to Ag+, but the fourth H2O prefers solvation through
hydrogen bonding. The preference of the tri-coordinated form is attributed
to the inefficient 5s–4d hybridization in Ag+, in contrast to the
efficient 4s–3d hybridization in Cu+. For Ag+(H2O)4,
however, di-coordinated isomers are identified in addition to the
tri-coordinated one. 相似文献
17.
A.R.W. Mc Kellar 《Applied physics. B, Lasers and optics》2008,90(2):213-225
Helium clusters, HeN-X, containing a probe molecule, X, are studied by infrared spectroscopy for the size range N≈1∼100. Spectra are observed
using a supersonic jet expansion and a tunable diode laser source operating in a rapid-scan (sweep integration) mode. The
pulsed jet uses a dilute gas mixture of the probe molecule in helium, with relatively high backing pressures (5–50 bar), and
a cooled (80–295 K) nozzle. Sensitivity is enhanced by multi-passing the laser beam through the jet with a toroidal mirror
system. The clusters are larger than van der Waals dimers and trimers, but smaller than those encountered in the field of
helium nanodroplets (N≈103–105). Furthermore, individual cluster sizes are resolved here, but not with nanodroplets, and infrared absorption is detected
directly (change in transmitted laser intensity), rather than indirectly (change in cluster fragmentation). Trends in the
spectra are described for five probe molecules, X=CO, SiH4, OCS, N2O, and CO2. Superfluid effects dominate for clusters larger than N≈8. Notable results include the unexpected observation of broad oscillations
in the effective rotational constants as a function of cluster size.
PACS 33.20.Ea; 34.30.+h; 36.40.Mr; 42.55.Px 相似文献
18.
A. P. Zazhogin A. A. Zazhogin A. I. Komyak D. S. Umreiko 《Journal of Applied Spectroscopy》2008,75(2):219-222
Results of studies on the effect of mechanochemical activation of ligand exchange processes in uranyl perchlorate-dimethylsulfoxide
are presented. Spectroscopic data show that mechanical activation of the exchange process in this system results in the replacement
of H2O in the first coordination sphere of uranyl UO22+ by DMSO to form nanocrystals with a defined ligand sphere. Possible factors governing the noted features are considered.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 213–216, March–April, 2008. 相似文献
19.
A. E. Galashev O. R. Rakhmanova 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(2):197-208
The molecular dynamics method is used to investigate the interaction of two, four, and six chloride ions with (H2O)50, clusters absorbing six ozone molecules. Chloride ions moving toward the cluster penetrate into it. The presence of ozone
increases the residence time of Cl− ions in the cluster. The duration of the perturbation increases with the number of Cl− ions surrounding the 6O3 + (H2O)50 system. The interaction with Cl− ions enhances the positional disorder of the molecules in the system and enhances the intensity of absorption and emission
of infrared radiation. These changes, however, are not monotonic function of the number of ions perturbing the system. As
a result of the interaction with Cl− ions, the integrated intensity of the Raman scattering on the (O3)6(H2O)50 cluster in the frequency range 0 ≤ ω ≤ 1100 cm−1 is significantly lower and the number of peaks in the spectrum is smaller. 相似文献
20.
Subhabrata Majumdar 《Pramana》2004,63(4):871-875
Surveys of clusters of galaxies provide us with a powerful probe of the density and nature of the dark energy. The red-shift
distribution of detected clusters is highly sensitive to the dark energy equation of state parameterw. Upcoming Sunyaev-Zel’dovich (SZ) surveys would provide us large yields of clusters to very high red-shifts. Self-calibration
of cluster scaling relations, possible for such a huge sample, would be able to constrain systematic biases on mass estimators.
Combining cluster red-shift abundance with limited mass follow-up and cluster mass power spectrum can then give constraints
onw, as well as onσ
8 and ΩM to a few per cents. 相似文献