共查询到20条相似文献,搜索用时 15 毫秒
1.
H. Hess K.R. Asmis T. Leisner L. Wöste 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):145-149
We present results on the ultrafast dynamics of mass-selected neutral Ag4 clusters using NeNePo (negative ion - neutral - positive ion) femtosecond pump-probe spectroscopy. One-color pump-probe spectra
of the Ag4
-/Ag4/Ag4
+ system measured at 385 nm and an internal cluster temperature of 20 K display a complex beat structure over more than 60
ps. The oscillatory structure is attributed to vibrational wave packet dynamics in an excited “dark" state of neutral Ag4. A dominant 740 fs wave packet period as well as wave packet dephasing and rephasing are observed in the spectra. Fourier
analysis of the spectra yields a group of frequencies centered around 45 cm-1 and an anharmonicity χ
e2νχ
eχ
e of 2.65 cm-1 for the active vibrational mode.
Received 30 November 2000 相似文献
2.
C. Bobbert C.P. Schulz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):95-97
Nam(H2O)n Clusters ( n = 1...200, m = 1...50) are formed in a recently build pick-up arrangement. Preformed water clusters traverse a sodium oven, where sodium
atoms are picked up. At low sodium vapour pressure ( < 1×10-4 mbar) pure Na(H2O)n clusters are observed in the mass spectra. At high sodium vapour pressure ( > 1×10-3 mbar) the water cluster pick up more than 50 Na atoms and reaction products Na(NaOH)n ( n = 2, 4...50) dominate the mass spectra. The even number of NaOH units in the products indicate that also in a finite cluster
the reaction occurs in pairs as in the macroscopic reaction.
Received 4 December 2000 相似文献
3.
P. Bogdanovich A. Kyniene R. Karazija R. Karpuskiene G. Gaigalas 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):175-183
The additional symmetry for the properties related to the ground state of the atom is considered taking into account many-electron
effects. Calculations of the I
4f, I
3d,I
2p,I
3p binding energies, 4f
N-15d - 4fN system differences and 2p, 3p electron affinities in the second order of perturbation theory and in the configuration interaction approximation have been
performed for the ground configurations with one open shell. The analysis of separate many-electron corrections for these
quantities and their variation along the sequences of atoms and ions shows that the main corrections maintain the considered
symmetry.
Received 18 January 1999 and Received in final form 17 July 1999 相似文献
4.
T. Rander M. Lundwall A. Lindblad G. Öhrwall M. Tchaplyguine S. Svensson O. Björneholm 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):253-257
Resonant Auger spectra of O2 clusters excited at the O1s edge are reported. After excitation to the repulsive 1s-13σ* state, the resulting resonant Auger spectrum displays features that remain constant in kinetic energy as the photon energy
is detuned. The shift between known atomic fragment features and these features is consistent with that observed for atoms
and clusters in singly charged states in direct photoemission. These findings are strong evidence for the existence of molecular
ultrafast dissociation processes within the clusters or on their surface. 相似文献
5.
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
6.
G.M. Koretsky M.B. Knickelbein 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):273-278
The photoionization spectra of Pr2-Pr21 and Ce2-Ce17 have been measured near threshold. The ionization potentials (IPs) of and vary discontinuously with size, but trend downward toward the work function of the bulk metals. In general, the IPs of cerium
clusters display more variation than those of praseodymium clusters. The sudden discontinuities observed in the IPs of both
and is akin to that displayed by clusters of transition metal atoms, suggesting that as in transition metal clusters, the rapid
evolution in geometric structure with size is the source of these discontinuities.
Received: 2 January 1998 / Accepted: 10 March 1998 相似文献
7.
C.M. Dion O. Dulieu D. Comparat W. de Souza Melo N. Vanhaecke P. Pillet R. Beuc S. Milošević G. Pichler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):365-370
We present the results of absorption measurements in a cesium vapor around 630 K, together with photoionization spectra through
a resonance-enhanced two-photon absorption of ultracold cesium dimers created after photoassociation of ultracold cesium atoms.
The maximum efficiency of the ultracold molecule ionization is found for wavelengths where absorption at thermal energies
is the strongest, in agreement with our theoretical simulations of both processes, involving the so-called Cs2 diffuse bands. This result will be helpful for further optimization of such a direct way of detection of ultracold molecules.
Received 13 September 2001 相似文献
8.
T.M. Di Palma A. Latini M. Satta A. Giardini-Guidoni 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(2):225-229
A photoionization study of the Me(NH3) clusters formed in the reaction of photoablated third group metal vapor with gaseous ammonia is reported. The photoionization
spectra exhibit some features due to vibrational excitation of ionic clusters and to transitions to neutral Rydberg states
leading to autoionization. DFT quantum chemical calculations are performed on the Me(NH3). The cluster geometries are fully optimized imposing the C3v symmetry. The calculated values of the IPs are in agreement with those experimentally determined.
Received: 16 February 1998 / Revised and Accepted: 7 May 1998 相似文献
9.
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
10.
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
11.
Yiwu Duan J.-M. Yuan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(3):319-326
Based on our previous work [Yiwu Duan, J.M. Yuan, C.G. Bao, Phys. Rev. A 52, 3497 (1995)], we study deeply the periodic orbits of the hydrogen molecular ion within the Born-Oppenheimer approximation
(BOA). The Thiele-Burrau's transformation is introduced to regularize the singularities associated with the Coulomb potential
terms and to transform the problem into a direct product of a pendulum and an anharmonic oscillator. This facilitates the
analysis of the bifurcation properties of the periodic orbits. Some more details are also given about the calculation of the
semiclassical density-of-state distribution using the Berry-Tabor formula.
Received: 5 February 1999 相似文献
12.
T. Nzeyimana E.A. Naji X. Urbain A. Le Padellec 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):315-325
Total cross-sections have been measured for the associative ionisation of C
+
+
O
-
, N
+
+
O
-
and O
+
+
O
-
by means of a merged-beam set-up operating with keV beams. These original measurements might be relevant to the understanding
of some astrophysical objects or laboratory-made plasmas (flames and etching plasmas). The magnitude of these cross-sections
is particularly large whatever the associating system, as these are in the range of 1×10
-14
cm2 at thermal energies. Their behaviour as a function of energy significantly differs from one system to another, and is characterised
by the Wigner law at low energy, and a rapid fall-off at higher energy due to competition with non-associative ionisation
processes.
Received 10 December 2001 and Received in final form 12 March 2002 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. 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
15.
K. Blaum G. Bollen F. Herfurth A. Kellerbauer H.-J. Kluge M. Kuckein E. Sauvan C. Scheidenberger L. Schweikhard 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):245-248
The cyclotron frequencies of singly charged carbon clusters Cn
+ (n ≥ 2) were measured with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The present limit of mass accuracy δm/m = 1.2 . 10-8 and the extent of the mass-dependent systematic shift (δm/m)sys = 1.7(0.6) . 10-10/u
. (m - m
ref) of the setup were investigated for the first time. In addition, absolute mass measurements by use of pure clusters of the
most abundant carbon isotope 12C are now possible at ISOLTRAP.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"Present address: CERN, CH-1211 Geneva 23, Switzerland; e-mail: klaus.blaum@cern.ch 相似文献
16.
W.T. Wallace R.L. Whetten 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):123-126
Smaller gold-cluster anions, typified by Au
7
-
, adsorb multiple CO molecules in a high-pressure, room-temperature flow-reactor, tending toward previously unknown saturation
compositions, Au7(CO)
4
-
. The weakness of the gold-carbonyl adsorption bond is evidenced indirectly by the high CO partial pressure required and more
directly by the high probability of fragmentation in the field-free flight region of the reflectron-type time-of-flight mass
spectrometer. The analysis of this metastability reveals that the actual distribution fN,M of products Au7(CO)
M
-
in the reactor may be highly non-statistical, e.g. with only even-M species present.
Received 17 April 2001 相似文献
17.
M.W. Mancini A.L. de Oliveira K.M.F. Magalhãaes V.S. Bagnato L.G. Marcassa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):317-322
In an experimental study, the multi-ionisation of metallic clusters (Nan) has been analysed in collisions with light ions in low charge states (H+, He+, He2+, O3+) at collision velocities below 1 a.u. Cluster ions are produced in charge states up to 5+. The average charge of the nano-particles
is found to increase linearly with the variation of projectile velocity and the square of the effective projectile charge,
well in agreement with the electronic stopping power of the bulk material. A fraction of 50% to 30% of the total projectile
energy loss (decreasing with velocity) is transferred into vibrational modes in good agreement with recent theoretical predictions.
Received 8 November 2000 and Received in final form 26 January 2001 相似文献
18.
19.
J.U. Andersen C. Gottrup K. Hansen P. Hvelplund M.O. Larsson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(2):189-204
Thermionic emission from hot fullerene anions, CN
-, has been measured in an electrostatic storage ring for even N values from 36 to 96. The decay is quenched by radiative cooling and hence the observations give information on the intensity
of thermal radiation from fullerenes. The experiments are analysed by comparison with a simulation which includes the quantisation
of photon energy and the statistics of emission. Experiments with heating of the molecules with a laser beam confirm the interpretation
of the observations in terms of radiative cooling and give an independent estimate of the cooling rate for C60
-. The measured cooling rates agree in general within a factor of two with the prediction from a classical dielectric model
of a thermal radiation intensity of ∼ 300 eV/s for C60 at 1 400 K, scaling approximately with the 6th power of the temperature and with the number of atoms in the molecule.
Received 12 March 2001 and Received in final form 12 June 2001 相似文献
20.
K. Ohshimo H. Tsunoyama F. Misaizu K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):107-110
Intracluster electron transfer and oligomerization reaction were investigated by mass spectrometry of clusters of alkali metal
atom (M) with acrylonitrile (AN; CH2=CHCN). In the photoionization mass spectra of M(AN)n, magic numbers were clearly observed at n = 3k (k = 1-4 for M = Na and K, k = 1 for M = Li). The results of photodissociation of neutral K(AN)n indicate that the n = 3 cluster has an anomalous stability relative to other sizes of clusters. The C=C bond in vinyl molecules is also found
to be necessary to form the magic numbers by measuring the photoionization mass spectrum of K atom with propionitrile. These
results strongly support the intracluster anionic oligomerization reaction initiated by electron transfer from the alkali
atom. The quantum chemical calculations have revealed that the evaporation induced by excess energy generated by intracluster
oligomerization is important to form the magic numbers in the present clusters.
Received 29 November 2000 相似文献