共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Bundhun P. Ramasami 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(3):355-364
A theoretical study of CnX, CnX+ and CnX- (X = O
and Se; n = 1-10) clusters is carried out employing the density functional
theory and the B3LYP functional. All species are fully optimized using the
basis set 6-31G(d) for all atoms and further, single-point computations are
done using the B3LYP/aug-cc-pVTZ level. Molecular properties such as
equilibrium parameters, dipole moment, infrared vibrational frequencies,
Raman activities and rotational constant are predicted. The computations
indicate that the equilibrium structures are either linear or quasi-linear.
We report the different forms of electron affinities, ionization energy,
atomization energy and binding energy of the CnO and CnSe chains.
The results indicate parity effect is very apparent for electron affinity,
ionization energy, and binding energy but the effect is less pronounced for
atomization energy. The n-even linear chains have larger ionization energy
and atomization energy than the n-odd ones but this effect is reversed for
electron affinity. The findings from this work are critically discussed and
they are very similar to those obtained previously for the hetero-atom doped
carbon chains. This research indicates that n-odd carbon chains are more
stable than n-even and this is the trend for the chalcogens carbon chains. 相似文献
2.
3.
Cross-sections, beam asymmetries, and recoil polarisations for the reactions γp → K
+Λ;γp → K
+Σ0, and γp → K
0Σ+ have been measured by the SAPHIR, CLAS, and LEPS Collaborations with high statistics and good angular coverage for centre-of-mass
energies between 1.6 and 2.3 GeV. The combined analysis of these data with data from π and η photoproduction reveals evidence
for new baryon resonances in this energy region. A new P11 state with mass 1840 MeV and width 140 MeV was observed contributing to most of the fitted reactions. The data demand the
presence of two D13 states at 1875 and, optimistically, at 2170 MeV. 相似文献
4.
Using 160GeV muon scattering data collected with the COMPASS experiment at CERN, the exclusive production of ωπ0 via virtual photons was studied. Selective population of a peak around 1250MeV is observed. Possible contributions from spin-parity
1- are searched for, inspecting decay angular correlations. In particular, the orientation of the ω decay plane may allow a
distinction from the 1+
b
1(1235) state. Our observation is compared with indications of a (1250) in annihilation and in γp .
Original article based on material presented at HADRON 2007. 相似文献
5.
A. B. Arbuzov E. A. Kuraev M. K. Volkov 《The European Physical Journal A - Hadrons and Nuclei》2011,47(9):103
The processes of electron-positron annihilation into π0γ and into π′(1300)γ are considered within an extended NJL model. The intermediate vector mesons ρ
0, ω
ρ′(1450), and ω(1420) are taken into account. The latter two mesons are treated as the first radial excited states. They are incorporated
into the NJL model by means of a polynomial form factor. Numerical predictions for the cross-sections of these processes are
received for the center-of-mass energies below 2 GeV. Our results for the π0γ production are in agreement with experimental data obtained in the energy region 600–1020 MeV. 相似文献
6.
Walter Bonivento 《Czechoslovak Journal of Physics》1999,49(2):49-60
A large number of measurement related to spin was performed during the last decade at the e + e ? colliders LEP and SLC providing important information on the dynamics of high energy interactions. In this paper three main topics will be covered: the measurements of the electroweak couplings, the study of fragmentation dynamics and the search for physics beyond the Standard Model. 相似文献
7.
E. P. Grigoriev 《Physics of Atomic Nuclei》2005,68(7):1087-1095
The 0? states in the 156Gd nucleus at E = 1952.38 keV and in the 158Gd nucleus at E = 2269.16 keV are established on the basis of an analysis of available data on even-even deformed nuclei. From data on the deexcitation of the levels and on the probability of their population by beta transitions, it is found that these states have a two-particle proton structure. A comparison of our data with information about the 0? levels in the 170Yb and 176Hf nuclei makes it possible to conclude that Jπ0? two-particle states exist at an excitation energy of about 2 MeV and higher. 相似文献
8.
We discuss the reaction π-e- → π-e-π0 with the purpose of obtaining information on the γπ → ππ anomalous amplitude
3π. We compare a full calculation at
(p6) in chiral perturbation theory and various phenomenological predictions with the existing data of Amendolia et al. By integrating our theory results using Monte Carlo techniques, we obtain σ = 2.05 nb at
(p6) and σ = 2.17 nb after including the dominant electromagnetic correction. Both results are in good agreement with the experimental cross-section of σ = (2.11±0.47) nb. On the basis of the ChPT results one would extract from the experimental cross-section as amplitudes
3π(0)extr = (9.9±1.1) GeV-3 and
3π(0)extr = (9.6±1.1) GeV-3, respectively, which have to be compared with the low-energy theorem
3π = e/(4π2Fπ3) = 9.72GeV-3. We emphasize the need for new data to allow for a comparison of experimental and theoretical distributions and to obtain
3π with smaller uncertainty. 相似文献
9.
We perform a theoretical study based on dispersion relations of the reaction γγ → π
0
π
0 emphasizing the low-energy region. We discuss how the ƒ
0(980) signal emerges in γγ → ππ within the dispersive approach and how this fixes to a large extent the phase of the isoscalar S-wave γγ → ππ amplitude above the threshold. This allows us to make sharper predictions for the cross-section at lower energies and our results could then
be used to distinguish between different ππ isoscalar S-wave parameterizations with the advent of new precise data on ππ → π
0
π
0. We compare our dispersive approach with an updated calculation employing the unitary chiral perturbation theory (U
gC
PT). We also pay special attention to the role played by the σ-resonance in γγ → ππ and calculate its coupling and width to γγ, for which we obtain Γ(σ → γγ) = (1.68 ± 0.15) keV. 相似文献
10.
W. Szajna M. Zachwieja 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(3):549-555
The high-resolution emission spectrum of the A1
Π–X1Σ+ transition of AlH was observed in the 18 000–25 000 cm-1 spectral region using a conventional spectroscopic
technique. The AlH molecules were excited in an Al hollow-cathode
lamp filled with a mixture of Ne carried gas and a trace amount of
NH3. The emission from the discharge was observed with a plane
grating spectrograph and recorded by a photomultiplier tube. In
total 163 transition wave numbers belonging to six bands (0-0,1
and 1-0,1,2,3) were precisely measured and rotationally
analysed. In the final fit the present data have been combined
with available high-resolution measurements of the
vibration-rotation bands by White et al. [J. Chem. Phys. 99,
8371 (1993)]. This procedure enabled extracting molecular
constants for the A1
Π and X1
Σ+ states of AlH. A very
slight local perturbation has been discovered in the v=1
vibration level of the A1
Π state at J=5. This was probably
caused by the interaction with the a3Π state. 相似文献
11.
Lukáš Pichl 《Czechoslovak Journal of Physics》2005,55(2):167-171
An accurate calculation of the lowest negative electronic state of H
2
-
(fixed nuclei) is reported using the CCSD(T) method and doubly augmented cc-pv5z basis set. Comparison has been made with the reference data by Senekowitsch et al. [Chem. Phys. Lett. 111 (1984) 211]. Owing to larger size of the basisset and inclusion of triple excitations, no vertical shift in this work is necessary to reproduce the asymptotics of H + H -. In addition, the effect of basis-set truncation is estimated, based on the complete-basis-set extrapolation method. The contribution of correlated electron-proton motion to the electron-energy curve for H2
– dynamics is pointed out.Dedicated to Prof. Jií Horáek on the occasion of his 60th birthday. 相似文献
12.
The catalogue of negative ions in superfluid helium has been extended using the example of Ar−, Kr−, and Xe−. Such objects cannot exist in vacuum, since the polarization attraction of an electron to the inert A atom is insufficient
for the formation of the bound state A−. However, these objects exist in helium as stable or metastable with a very long lifetime. The effect is due to the electron
localization in liquid helium. If a mixture of excited A* atoms and electrons is prepared in the gas phase above liquid helium,
the reaction A* + e = A*− becomes possible for all atoms of the periodic table. Such charges can be immersed into liquid helium by the electric field.
In this case, the radiative decay A*− = A + e allowed in vacuum can be forbidden in liquid. This leads to the formation of the new unique objects A−, which can exist in liquid helium but are absent in nature. The size of such charged formations has been determined and is
close the radius of a usual electron bubble in helium. 相似文献
13.
I.?Man?ev 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):213-218
The total cross sections for charge transfer in Li2+-H and He+-He+ collisions have been calculated, using the four body first Born approximation with correct boundary conditions (CB1-4B) and
four body continuum distorted wave method (CDW-4B) in the energy range 10–5000 keV/amu. The role of dynamic electron correlations
is examined as a function of the impact energy. The present results call for additional experimental data at higher impact
energies than presently available. 相似文献
14.
E. P. Grigoriev 《Physics of Atomic Nuclei》2003,66(9):1705-1714
For the 156Gd and 170Yb nuclei, where the inversion of levels in the Kπ=1? bands is observed, the energies of rotational levels are calculated on the basis of the Coriolis interaction model for the states of two bands whose quantum numbers are Kπ=1?. New 0? levels are introduced in 170Yb, and the structure of 170Er is refined. The interaction parameters calculated for six nuclei are considered within the structure predicted by the quasiparticle-phonon model. 相似文献
15.
V. P. Tarasov G. A. Kirakosyan 《Russian Journal of Physical Chemistry B, Focus on Physics》2016,10(4):582-586
The effect of the 16O ? 18O substitution in the coordination sphere of permanganate anion MnO 4 ? on the chemical shift of 55Mn nuclei have been studied by 17O and 55Mn NMR. Time constants τ n,k of oxygen exchange in the water–permanganate anion system have been estimated. In nearly neutral solutions (pH ≈ 6.8–7.2), the oxygen exchange time is on the order of tens of hours. Bubbling gaseous HCl through this solution for a few seconds leads to the equilibrium distribution of oxygen isotopes in the manganese coordination sphere. The observed temperature dependences of isotope-induced 55Mn NMR shifts in Mn16 O 44-n 18 O n – (n = 0–4) have been treated as a result of rovibrational averaging of Mn–O bond lengths. The change in the Mn—O bond length in caused by the 16O → 18O isotope substitution is on the order of 10–4 Å. 相似文献
16.
Combining the Okubo-Zweig-Iizuka rule in the decay φ→ρπ→π+π?π0 with the ρ→4π decay amplitudes, we calculate the φ→2π+2π?π0 and φ→π+π?3π0 ones. The partial widths of the above φ decays are evaluated, and the excitation curves in e+e? annihilation are obtained, assuming reasonable particular relations among the parameters characterizing the anomalous terms of the HLS Lagrangian. The evaluated branching ratios Bφ→π+π?3π0 ≈ 2 × 10?7 and Bφ→2π+2π?π0 ≈ 7 × 10?7 are such that, with the luminosity L=500 pb?1 attained at DAΦNE φ factory, one may already possess about 1685 events of the decays φ→5π. 相似文献
17.
Zhi-Gang Wang Shao-Long Wan 《The European Physical Journal C - Particles and Fields》2007,50(4):781-791
In this article, we calculate the vector form factors f+
Kπ(Q2) and f-
Kπ(Q2) within the framework of the light-cone QCD sum rule approach. The numerical values of f+
Kπ(Q2) are compatible with existing theoretical calculations, and the central value of f+
Kπ(0) (f+
Kπ(0)=0.97) is in excellent agreement with the values from chiral perturbation theory and lattice QCD. The values of |f-
Kπ(0)| are very large compared to the theoretical calculations and experimental data, and they cannot give any reliable prediction.
At large momentum transfer with Q2 > 5 GeV2, the form factors f+
Kπ(Q2) and |f-
Kπ(Q2)| can either show the asymptotic behavior of or decrease more quickly than ; more experimental data are needed to select the ideal sum rules.
PACS 12.38.Lg; 12.38.Bx; 12.15.Hh 相似文献
18.
I. D. Petrov V. L. Sukhorukov M. W. Ruf H. Hotop 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(3):289-302
Absolute photoionization cross sections for Ne atoms in the excited
levels (Paschen notation
) were calculated at near threshold energies within
the configuration interaction Pauli-Fock approach including core polarization.
The computed spectra and the lineshape parameters of the odd parity
2p1/2
5ns′/d′ autoionizing resonances are
found to be in good agreement with high resolution laser spectroscopic
results. Guided by the theoretical results, improved analyses of the measured
spectra by superimposed Fano-type profiles were achieved. Theoretical
predictions are presented for resonances which have not yet been studied
experimentally. In addition, we report the absolute partial photoionization
cross sections for the 2P3/2 and 2P1/2 channel at
photoelectron energies up to 7 eV. Except for the highest lying 2p1(1S0) level, these cross sections monotonically decrease with
energy (as reported earlier in single-electron calculations for the
Ne(2p53p) configuration) with branching ratios which essentially reflect
the core composition of the 2px levels. For the 2p1 level the resonance structure and the
partial cross sections are strongly influenced by a
Cooper-Seaton minimum in the d3/2
′ channel,located just above the 2P1/2 ionization limit. 相似文献
19.
V. I. Murav’ev 《Physics of the Solid State》2004,46(5):853-857
The parameters of hyperfine interactions in Pb3+F 8 ? F a ? tetragonal clusters of MeF2 crystals (Me=Ca, Sr, Ba) are interpreted. The contributions of the spin polarization to the parameters of the proper hyperfine interaction and additional (ligand) hyperfine interactions are calculated in the approximation of weak binding between a charge-compensating ion F a ? and a cubic fragment in the tetragonal cluster. It is demonstrated that correct inclusion of the contributions from the spin polarization to the ligand isotropic hyperfine interaction for the F a ? ion leads to anomalously large parameters of this interaction for MeF2 crystals. These results are in agreement with experimental data. 相似文献
20.
Bose-Einstein correlations (BEC) between final state particles in the reaction
have been studied. Data corresponding to a total integrated luminosity of 550 pb-1, recorded by the DELPHI detector at centre-of-mass energies ranging from 189 to 209 GeV, were analysed. An indication for
inter-W BEC between like-sign particles has been found at the level of 2.4 standard deviations of the combined statistical
and systematic uncertainties.
Received: 11 January 2005, Revised: 13 July 2005, Published online: 13 September 2005
This paper is dedicated to the late Frans Verbeure.
Frans was a very active member of the DELPHI collaboration and its QCD
and WW working groups. The loss of Frans touched us all deeply. 相似文献