共查询到20条相似文献,搜索用时 15 毫秒
1.
I. Sherstov S. Liu Ch. Lisdat H. Schnatz S. Jung H. Knöckel E. Tiemann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):485-492
Absolute transition frequencies of the b 3Π(0u
+) - X 1Σg
+ system of K2 were measured in a molecular beam with Lamb dip absorption spectroscopy applying a frequency comb from a femtosecond pulsed
laser. Both, K atoms and K2 molecules are present in the beam and are expected to interact by collisions. The atoms can be deflected optically out of
the beam, and thus the collision rate between K atoms and K2 molecules is changed by about an order of magnitude. The molecular transition frequencies for low collisional rate are compared
with those for high one. Limits for the collisional frequency shift within the beam are determined. 相似文献
2.
M. A. Kalyar S. Mahmood S.-U. Haq N. Amin M. A. Baig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):229-236
We report a systematic line shape analysis study of the 6p7p configuration
based 1P1, 3D1 and 3P1 autoionizing
resonances in barium using a Nd:YAG pumped dye laser system in conjunction
with a thermionic diode ion detector. The even parity isolated autoionizing
resonances have been approached via four intermediate states 6 snp
1P1 (6 ≤n ≤8) and 5d6p 1P1. A comparison of
the Fano parameters of the resonance profiles reveals that the width of an
autoionizing resonance is independent of the excitation path while the line
profile parameter changes with the selection of different intermediate
states. 相似文献
3.
The narrow D
s0
* (2317) and broad D
0
* (2300-2400) charmed scalar mesons and their radial excitations are described in a coupled-channel quark model that also reproduces
the properties of the light scalar nonet. All two-meson channels containing ground-state pseudoscalars and vectors are included.
The parameters are chosen fixed at published values, except for the overall coupling constant λ, which is fine-tuned to reproduce the D
s0
* (2317) mass, and a damping constant α for subthreshold contributions. Variations of λ and D
0
* (2300-2400) pole postions are studied for different α values. Calculated cross-sections for S-wave DK and Dπ scattering, as well as resonance pole positions, are given for the value of α that fits the light scalars. The thus predicted radially excited state D
s0
*′(2850), with a width of about 50MeV, seems to have been observed already. 相似文献
4.
5.
L. Seetha Lakshmi K. Dörr K. Nenkov A. Handstein V. S. Sastry K.-H. Müller 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):115-121
We report the charge state modification effects at the Mn site on the ground
state properties of colossal magnetoresistive manganites. Ta5+
substitution results in an appreciable increase in the lattice parameters
and unit cell volume due to increased Mn3+ concentration. The
ferromagnetic-metallic ground state modifies to a cluster glass insulator
for
. The reduction in the transition temperatures with
increasing x is ∼39 K/at.%. Besides the modification of majority carrier concentration due to increased Mn3+ concentration and enhanced local structural effects, the local
electrostatic potential of the substituent seems to contribute to the
unusually strong reduction of the transition temperatures of the compounds.
Thermo magnetic irreversibility just below Curie temperature (Tc),
non-saturation of magnetization, two distinct magnetic transitions in ac
susceptibility in an appropriate static field: close to Tc and other at
low temperature (the spin freezing temperature (Tg)) and non-stationary
dynamics with a characteristic maximum in the magnetic viscosity close to
Tg confirm a cluster glass state for
. These results
find additional support from a linear low temperature magnetic specific heat
of x = 0.10 with a characteristic broad maximum close to Tg. 相似文献
6.
M. Sabidó J. de Andrés J. Sogas J. M. Lucas M. Albertí J. M. Bofill I. Rabadán A. Aguilar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):63-70
The dynamics of collisional processes between Mg atoms and caesium ions is studied using the hemiquantal (HQ) approach with
special attention to the collisional channels leading to Mg(3 1P) and Cs(6 2P) states, for which the corresponding emission excitation functions have been previously measured in our laboratory. The
radial and angular non-adiabatic couplings between the manifold of quasimolecular states have been determined using an ab
initio configuration interaction calculation. The cross-sections for the different channels, as a function of the laboratory
collisional energy, are compared with experimental values. The dynamical calculations indicate that, for the inelastic processes
considered, the range of relevant impact parameters is small, active collisions being of the head-on type.
. 相似文献
7.
It is found that the scattering of the fragile nucleus 6Li from 12C
and 16O is unexpectedly transparent.
It is shown that the internal-wave
contribution is significantly large in the scattering,
which suggests that some transparency could persist in the scattering
involving the fragile nucleus 6He. 相似文献
8.
F. A. Bischoff O. Hübner W. Klopper L. Schnelzer B. Pilawa M. Horvatić C. Berthier 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):229-235
The quadrupole splitting in the 23Na nuclear magnetic resonance (NMR)
spectrum of the hexanuclear ferric wheel
Na@Fe6(tea)6
+ has been computed via an evaluation of the electric-field gradient (EFG) at the Na nucleus in the
framework of density-functional theory (DFT). The simulated spectrum is compared with experimental data.
A total of 26 = 64 Kohn-Sham determinants (a number that reduces to eight symmetry-unique determinants due to the
high S6 symmetry of the ferric wheel) with six localised high-spin Fe(III) centres (S = 5/2) could be
optimised in a self-consistent manner, and the corresponding DFT energies of all of these (broken-symmetry)
determinants coincide almost perfectly according to the Ising Hamiltonian solutions, especially when the energy
is computed from the B3LYP functional. The EFG at the Na atom
does not depend much on the specific Kohn-Sham determinant but depends on the
geometry of the ferric wheel and on the basis set used in the DFT calculations (particularly with regard to the atomic functions
on the Na atom). 相似文献
9.
M. Požek A. Dulčić A. Hamzić M. Basletić E. Tafra G. V.M. Williams S. Krämer 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(1):1-7
Strongly underdoped RuSr1.9La0.1GdCu2O8 has been comprehensively studied by dc magnetization, microwave measurements, magnetoresistivity and Hall resistivity in
fields up to 9 T and temperatures down to 1.75 K. Electron doping by La reduces the hole concentration in the CuO2 planes and completely suppresses superconductivity. Microwave absorption, dc resistivity and ordinary Hall effect data indicate
that the carrier concentration is reduced and a semiconductor-like temperature dependence is observed. Two magnetic ordering
transitions are observed. The ruthenium sublattice orders antiferromagnetically at 155 K in low applied magnetic fields, and
the gadolinium sublattice orders antiferromagnetically at 2.8 K. The magnetoresistivity in this compound exhibits a complicated
temperature dependence due to the occurence of the two magnetic orders and spin fluctuations. It is shown that the ruthenium
magnetism influences the conductivity in the RuO2 layers while the gadolinium magnetism influences the conductivity in the CuO2 layers. The magnetoresistivity is isotropic above 4 K, but it becomes anisotropic close to the gadolinium antiferromagnetic
order temperature. 相似文献
10.
A. Shumelyuk D. Barilov S. Odoulov E. Krätzig 《Applied physics. B, Lasers and optics》2003,76(4):417-421
We apply, for the first time to our knowledge, photorefractive grating spectroscopy to obtain not-yet-known data on the anisotropy
of the dielectric permittivity of Sn2P2S6. Two independent techniques are used, one based on measurements of the amplitude of the space-charge field grating as a function
of grating spacing and the other based on measurements of the grating decay time, also as a function of grating spacing. Both
techniques provide close values for the anisotropy, which appears to be well pronounced, a ratio εxx/εzz≈4 is revealed for two of the three independent components of the dielectric tensor. Our data also allow us to conclude that
the charge mobility is nearly isotropic in the same plane, μxx/μzz≈1.
Received: 2 December 2002 / Published online: 26 March 2003
RID="*"
ID="*"Corresponding author. Fax: +380-44/265-2359, E-mail: odoulov@iop.kiev.ua 相似文献
11.
M.D. Di Rosa S.G. Crane J.J. Kitten W.A. Taylor D.J. Vieira X. Zhao 《Applied physics. B, Lasers and optics》2003,76(1):45-55
We report the first magneto-optical trapping of radioactive 135Cs and 137Cs and a promising means for detecting these isotopes at ultra-sensitive levels by coupling a magneto-optical trap (MOT) to
a mass separator. A sample containing both isotopes was placed in the source of a mass separator, ionized, mass-separated,
and implanted in a Zr foil within the trapping cell. After implantation, atoms were released from the foil by inductive heating
and then captured in a MOT that used large-diameter beams and a dry-film-coated cell to achieve high trapping efficiency.
Trapped-atom numbers in the case of either isotope ranged from 104 to 107, as determined from the MOT fluorescence signal. Over this trapped-atom range, the MOT fluorescence signal was found to increase
linearly with the number of atoms implanted in the foil and without isotopic bias to within 4%. In principle, this method
can then provide a measurement of the 137Cs/135Cs ratio accurate to within 4% through the direct ratio of MOT fluorescence signals. The fluorescence signal from stable 133Cs, when implanted and released from the foil, was suppressed relative to MOT signals by more than seven orders of magnitude
when the system was tuned to trap 135Cs or 137Cs. When combined with the isotopic selectivity of ≥105 for the mass separator, the overall suppression of 133Cs is expected to exceed 1012. At present our system delivers atoms from sample to MOT with an efficiency of 0.5%, has a trapped-atom detection limit of
4000 atoms, and achieves a sample-detection sensitivity of one million atoms.
Received: 23 August 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +1-505/667-0440, E-mail: mdd@lanl.gov 相似文献
12.
A. Geddo Lehmann C. Sanna N. Lampis F. Congiu G. Concas L. Maritato C. Aruta A. Yu. Petrov 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):337-345
Thin films of La0.7Sr0.3MnO3 were grown by
molecular beam epitaxy on (001)LaAlO3 crystals. High resolution X-ray
diffraction analysis proves the presence of twins in the films at room
temperature, showing that the twin structure of the substrate which forms at
the
ferroelastic transition at TF = 813 K
served as a template for the film microstructure. Magnetic measurements
indicate a thermomagnetic irreversibility which is ascribed to the quenched
disorder related to twinning and discussed in terms of coexisting
ferromagnetic and spin disordered regions connected with the undeformed
domain cores and strained domain walls respectively. 相似文献
13.
M. J.G. Borge M. Alcorta H. O.U. Fynbo G. Garcia H. B. Jeppesen O. Kirsebom M. Madurga G. Nyman D. Obradors O. Tengblad 《The European physical journal. Special topics》2007,150(1):207-210
We have studied 12C in full kinematics via the 10B(3He,pααα)
reaction at an energy of 2.45 MeV. In our data we have identified states in 12C
from the ground state up to about 18 MeV, with spins ranging from 0 to 4.
Due to the very good resolution, we are able to determine properties of
these 12C resonances, such as their energy, width, and spin.
In this contribution preliminary results from the ongoing analysis are presented.
Main focus on the precise determination of the breakup spectra for all resonances. 相似文献
14.
E. Govea-Alcaide I. García-Fornaris P. Muné R. F. Jardim 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):373-378
Measurements of the electrical resistivity as a function
of temperature, ρ(T), for different values of applied
magnetic field, Ba (0 ≤ Ba ≤ 50 mT), were performed in
polycrystalline samples of Bi1.65Pb0.35Sr2Ca2
Cu3O10+δ subjected to different uniaxial compacting
pressure (UCP). We have found appreciable differences in the grain
orientation between samples by using X-ray diffractometry. From
the X-ray diffraction patterns performed, in powder and pellet
samples, we have estimated the Lotgering factor along the (00l)
direction, F(00l). The results indicate that F(00l)
increases ~23% with increasing UCP suggesting that grains
of these samples are preferentially aligned along the c-axis,
which is parallel to the compacting direction. The resistive
transition of the samples have been interpreted in terms of the
thermally activated flux-creep model. In addition, the effective
intergranular pinning energy, U0, have been determined for
different applied magnetic field. The magnetic field dependence of
U0, for Ba > 8 mT, was found to follow a H- α
dependence with α = 0.5 for all samples. The analysis of the
experimental data strongly suggested that increasing UCP results
in appreciable changes in both the grain alignment and the grain
connectivity of the samples. We have successfully interpreted the
data by considering the existence of three different
superconducting levels within the samples: the superconducting
grains, the weak-links, and the superconducting clusters. 相似文献
15.
I. V. Kedyk P. Mathey G. Gadret A. A. Grabar K. V. Fedyo I. M. Stoika I. P. Prits Y. M. Vysochanskii 《Applied physics. B, Lasers and optics》2008,92(4):549-554
In this work we report results on electro-physical, optical and photorefractive investigations for Sb-doped Sn2P2S6 crystals. The crystals are obtained by two methods: the vapour-transport technique and the Bridgman technique using stoichiometric
Sn2P2S6 composition with different amounts of antimony in the initial compound. The good optical quality of the crystals obtained
with the Bridgman technique is underlined. The dependences of the photorefractive two-beam coupling coefficient and the grating
build-up time are investigated at the wavelength of 633 nm. It is found that the sample doped with 1.5% of Sb is characterized
by an optimal combination of the main photorefractive parameters exhibiting a fairly high two-beam coupling coefficient (up
to 20 cm−1) and a short response time (1.3 ms) that is the shortest among all the previously studied Sn2P2S6 crystals in the red spectral region. 相似文献
16.
17.
X. H. Ren J. T. Zhang Y. Wang Z. Z. Xu D. S. Guo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):401-407
We study the photoelectron angular distributions (PADs) of diatomic molecule
H2
+ irradiated by intense laser fields using a nonperturbative
scattering theory. We find that the internuclear vector may change the PADs.
The PADs have qualitative changes with the increasing of the internuclear
distance. The molecular orientation affect the symmetry of the PADs. When the
internuclear vector is vertical or parallel to the laser polarization vector,
the PADs are four-fold symmetric; for other case the PADs are two-fold
symmetric. Due to the modulation effect resulting from the molecular
multi-core nature, the size of the jet and the main lobe can be enlarged or
reduced. The molecular modulation effect become obvious for large
internuclear distance. 相似文献
18.
A. Ioffe O. Ermakov I. Karpikhin P. Krupchitsky P. Mikula P. Lukas M. Vrana 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):197-200
Excited states of 68Ga have been investigated through the 55Mn(16O, 2pn) reaction at projectile energy 55 MeV. The level scheme has been extended up to 7.8 MeV. Altogether six new excited
levels could be identified and twelve previously unobserved γ-transitions have been placed in the modified level scheme.
Received: 19 June 2000 / Accepted: 20 October 2000 相似文献
19.
A.-S. Rüetschi D. Jaccard 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(1):43-49
High pressure resistivity measurements of the organic compound (TMTTF)2BF4 have been performed in a newly developped Bridgman cell providing good pressure conditions on a wide pressure range. For
the first time in this compound a zero resistance superconducting state is observed between 3 and 4 GPa. At temperatures above
the superconducting transition, the resistivities of the two high quality samples show a different behavior. One sample, provides
indications for a magnetic quantum critical point at the maximum of Tc, whereas in the other antiferromagnetic spin-fluctuations are present above Tc. 相似文献
20.
P. Jesinger Yu. N. Kopatch M. Mutterer F. Gönnenwein A. M. Gagarski J. v. Kalben V. Nesvizhevsky G. A. Petrov W. H. Trzaska H. -J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2005,24(3):379-388
Experiments have been performed for studying quaternary fission (QF) in spontaneous fission of 252Cf, on the one hand, and for the neutron-induced fission reactions 233, 235U(nth, f ), on the other hand. In this higher-multiplicity fission mode, by definition, four charged products appear in the final state. In other words, as a generalization of the ternary-fission process, not only one but two light charged particles (LCPs) are accompanying the splitting of an actinide nucleus into the customary pair of fission fragments. In the two sets of measurements, which have used quite different approaches, the yields of several QF reactions with α-particles and tritons as the LCPs have been determined and the corresponding kinetic-energy distributions of the α-particles measured. The QF process can appear in two basically different ways: i) the simultaneous creation of two LCPs in the act of fission (“true” QF) and ii) via a fast sequential decay of a single but particle-unstable LCP in common ternary fission (“pseudo” QF). Experimentally the two varieties of QF have been distinguished by exploiting the different patterns of angular correlations between the two outgoing LCPs. The experiments described in the present paper are the first to demonstrate that both types of reactions, true and pseudo QF, occur with quite comparable probabilities. As a new result also, the kinetic-energy distributions related to the two processes have been shown to be significantly different. For all QF reactions which could be explored, the yields for 252Cf(sf) were found to be roughly by an order of magnitude larger than the yields found in the 233U(nth, f ) and 235U(nth, f ) reactions. An interesting by-product has been the measurement of yields of excited LCPs which allows to deduce nuclear temperatures at scission by comparison to the respective yields in the ground state. 相似文献