共查询到20条相似文献,搜索用时 78 毫秒
1.
Z.G. Zhang A. Persson Z.S. Li S. Svanberg Jiang Zhankui 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):301-304
Natural radiative lifetimes of 20 levels (energy range between 29 000-35 000 cm-1) in Gd II and 5 levels (energy range between 43 000-49 000 cm-1) in Gd III have been measured using time-resolved laser-induced fluorescence in a laser-produced plasma.
Received 17 July 2000 and Received in final form 13 October 2000 相似文献
2.
J. Lal D. Abernathy L. Auvray O. Diat G. Grübel 《The European physical journal. E, Soft matter》2001,4(3):263-271
We have studied the static and dynamic behaviour of magnetic colloidal systems (ferrofluids) by Small-Angle X-ray Scattering
(SAXS) and X-ray Photon Correlation Spectroscopy (XPCS). The main features of the novel XPCS technique will be illustrated
by data taken on a model system, colloidal silica spheres. We will then present the results obtained on an optically opaque
suspension of magnetic colloids (maghemite) in the wave vector range from 10-3 to 10-2?^-1. Translational diffusion in zero field and anisotropic diffusion under external magnetic fields will be discussed.
Received 9 August 1999 and Received in final form 26 July 2000 相似文献
3.
B. Yedierler S. Bilikmen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):367-371
The limits put by optical guiding, and channel guiding mechanisms on the Laser Wakefield Acceleration (LWFA) technique are
imposed on the Resonant Laser Wakefield Acceleration (RLWFA) scheme. Energy gained by the electrons in both schemes are calculated
and compared. It has presented that in the RLWFA case, the electrons gain more and more energy after each traversal of the
laser pulse and the electrons in a plasma gain about 3 GeV after 10 passages of the laser pulse. They gain 13 GeV when the
laser light makes 50 passages and 26 GeV after the laser beam traverses the plasma 100 times. Moreover, the channel guiding
mechanism is integrated to the RLWFA scheme and together with diffraction guiding a model for electron acceleration is proposed.
Received 13 September 2000 and Received in final form 27 October 2000 相似文献
4.
P. Orgiani C. Aruta G. Balestrino S. Lavanga P.G. Medaglia A. Tebano 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):23-28
Transport properties of SrRuO3 thin films were studied as a function of the epitaxial strain. SrRuO3 films were grown on (100) SrTiO3 substrates by the Pulsed Laser Deposition technique equipped with Reflection High Energy Electrons Diffraction (RHEED). Samples
thickness has been varied from a few unit cells to above 1000 ? while monitoring RHEED intensity oscillations. In thicker
films epitaxial strain was found to be progressively relaxed. SrRuO3 relaxed films (thickness 1000 ?) show metallic behavior for the whole temperature range with a ferromagnetic ordering at about 150 K. For thinner
films, ferromagnetic ordering occurs at progressively lower temperatures, until in films thinner than 400 ? it disappears.
Films thinner than 80 ? show a semiconducting behavior at low temperatures. Our results provide direct evidence of the crucial
role of the strain effect for conducting and magnetic properties of SrRuO3.
Received 16 July 2001 and Received in final form 22 October 2001 相似文献
5.
M. Bonelli A.C. Ferrari A. Fioravanti A. Li Bassi A. Miotello P.M. Ossi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(3):269-280
Tetrahedral amorphous carbon films have been produced by pulsed laser deposition, at a wavelength of 248 nm, ablating highly
oriented pyrolytic graphite at room temperature, in a 10-2 Pa vacuum, at fluences ranging between 0.5 and 35 Jcm-2. Both (100) Si wafers and wafers covered with a SiC polycrystalline interlayer were used as substrates. Film structure was
investigated by Raman spectroscopy at different excitation wavelength from 633 nm to 229 nm and by transmission Electron Energy
Loss Spectroscopy. The films, which are hydrogen-free, as shown by Fourier Transform Infrared Spectroscopy, undergo a transition
from mainly disordered graphitic to up to 80% tetrahedral amorphous carbon (ta-C) above a threshold laser fluence of 5 J cm-2. By X-ray reflectivity roughness, density and cross-sectional layering of selected samples were studied. Film hardness as
high as 70 GPa was obtained by nanoindentation on films deposited with the SiC interlayer. By scratch test film adhesion and
friction coefficients between 0.06 and 0.11 were measured. By profilometry we obtained residual stress values not higher than
2 GPa in as-deposited 80% sp3 ta-C films.
Received 25 June 2001 相似文献
6.
M. Oba K. Akaoka M. Miyabe I. Wakaida 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):255-260
The laser induced fluorescence method using atomic beam combined with Doppler-free two-photon absorption technique was applied
for the measurement of isotope shifts and hyperfine structures of atomic uranium including 234U, 235U, 236U and 238U isotopes. The isotope shifts between 238U-234U, 238U-235U, 238U-236U, and the hyperfine structure of 235U were obtained in the high lying odd levels around 4 eV.
Received 3 December 2001 / Received in final form 4 July 2002 Published online 29 October 2002
RID="a"
ID="a"e-mail: oba@analchem.tokai.jaeri.go.jp 相似文献
7.
S. Galluccio 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(4):595-600
We consider the problem of option pricing when the underlying asset follows a general semimartingale process. After reviewing
the foundations of arbitrage pricing theory for semimartingales and the link with Lévy processes, we introduce a general method
to price options in this framework based on Fourier and Wavelet analysis.
Received 4 September 2000 相似文献
8.
T.J. Davis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):111-118
The diffraction of laser-cooled atoms from a spatially-periodic potential is modelled using rigorous coupled-wave analysis.
This numerical technique, normally applied to light-diffraction, is adapted for use with atomic de Broglie waves incident
on a reflecting diffraction grating. The technique approximates the potential by a large number of constant layers and successively
solves the complex eigenvalue problem in each layer, propagating the solution up to the surface of the grating. The method
enables the diffraction efficiencies to be calculated for any periodic potential. The results from the numerical model are
compared with the thin phase-grating approximation formulae for evanescent light-wave diffraction gratings and idealised magnetic
diffraction gratings. The model is applied to the problem of diffracting Rb atoms from a grating made from an array of permanent
magnets.
Received 13 June 2000 and Received in final form 15 December 2000 相似文献
9.
P.L. Christiansen Y.B. Gaididei F.G. Mertens S.F. Mingaleev 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):545-553
We investigate the properties of nonlinear excitations in different types of soliton carrying systems with long-range dispersive interactions. We show that length-scale competition in such systems, universally results in a multi-component structure of nonlinear excitations
which may lead to a new type of multistability: coexistence of different nonlinear excitations at the same value of the spectral parameter (i.e., velocity in the case of anharmonic lattices or frequency in nonlinear Schr?dinger models).
Received 31 August 2000 and Received in final form 14 December 2000 相似文献
10.
Z.G. Zhang Z.S. Li S. Svanberg P. Palmeri P. Quinet E. Biémont 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):301-305
Lifetimes of three levels belonging to the configuration 4f
135d with J = 1 in Yb III have been measured for the first time using the time-resolved laser-induced fluorescence method. Experimental
transition probabilities have been deduced for the transitions between the levels studied and the ground state. The comparison
of the experimental lifetimes with theoretical data, deduced within the relativistic Hartree-Fock (HFR) approach, underlines
the dramatic importance of an adequate consideration of core-polarization effects in the theoretical model and the sensitivity
of one of the lifetime values to small correlation effects.
Received 2 April 2001 相似文献
11.
N. Beverini E. Maccioni F. Sorrentino V. Baraulia M. Coca 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):223-228
We have measured the ratio between the transition probabilities of two forbidden lines in Ca: the intercombination line at
657.3 nm and the E
2 line at 457.5 nm. The value we obtained for this ratio is (54.1±2.4). Combined with the most accurate value available in literature for the lifetime of the
3
P
1
level, our measurement gives a value of (54.4±4.0) s-1 for the
1
S
0
↦
1
D
2
transition probability, significantly more accurate than the previous determinations.
Received 17 June 2002 / Received in final form 9 December 2002 Published online 4 March 2003 相似文献
12.
L.M. Blinov M.I. Barnik H. Ohoka M. Ozaki N.M. Shtykov K. Yoshino 《The European physical journal. E, Soft matter》2001,4(2):183-192
The temperature dependence of the surface polarization has been measured for both the planar and homeotropic orientation of
a nematic liquid crystal at a solid substrate. A conventional liquid crystal 5CB, pure and doped with an azo-dye, was used
in cells with controlled asymmetry for light absorption. The measurements have been made by a pyroelectric technique using
short pulses of a YAG laser to create a temperature increment. The latter, in turn, was measured independently by a novel
time-resolved “optical thermometer” technique monitoring temperature-dependent birefringence by a He- Ne laser beam. In accordance
with the symmetry of the order parameter, the surface polarization has different sign for the two orientations, its magnitude
ranges from -4 to +2pC/m. The same technique has been used for the measurement of the flexoelectric polarization in hybrid
cells. The sum of the flexoelectric coefficients is e
1 + e
3 = - 13pC/m at 25°C.
Received 28 February 2000 and Received in final form 5 September 2000 相似文献
13.
B. Ketzer T. von Egidy F.J. Hartmann C. Maierl R. Pohl J. Eades E. Widmann T. Yamazaki M. Kumakura N. Morita R.S. Hayano M. Hori T. Ishikawa H.A. Torii I. Sugai D. Horváth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):305-316
The quenching of metastable states of antiprotonic helium by collisions with hydrogen and deuterium molecules was studied.
A systematic investigation of the delayed annihilation time spectra at various H2 and D2 admixture ratios at the ppm level revealed characteristic changes of their shape, which indicated a strong principal and
orbital quantum number dependent quenching of levels in both cases. Applying a laser spectroscopy technique to measure the
lifetimes of individual states and cascades we deduced H2 and D2 quenching cross-sections for the states (n, l )= (39, 35) and (37, 34). These cross-sections establish for D2 molecules the strong increase of the quenching efficiency with increasing principal quantum number n of the state under investigation previously reported for the case of H2 admixtures. Our experiments indicate that the low-n state (37, 34) is somewhat less affected by D2 than by H2, while the high-n state (39, 35) is equally quenched by both isotopes.
Received 2 October 2000 相似文献
14.
W. Cui Y. Hu C. Lifshitz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):565-571
A new instrument has been constructed whose purpose is to study time-resolved photodissociation (TRPD) of small peptide ions.
Laser desorption of neutral peptides is combined with laser photoionization in an ion trap followed by thermalization, laser
photodissociation and time of flight mass analysis. Ionization and excitation take place through an aromatic chromophore at
the C-terminus of the peptide whereas dissociation produces the immonium ion at the N-terminus. The long-range purpose is
to uncover the role of IVR in unimolecular fragmentations of peptide radical cations. One avenue is the determination of microcanonical
rate constants at a well-defined internal energy E for a series of peptides possessing the same chromophore, undergoing the same fragmentation but having a variable number
of degrees of freedom. This paper demonstrates the feasibility of the method and provides the first attempts at rate measurements
for the peptide leucyl tyrosine (LeuTyr).
Received 6 January 2002 Published online 13 September 2002 相似文献
15.
J.F. Bobo D. Basso E. Snoeck C. Gatel D. Hrabovsky J.L. Gauffier L. Ressier R. Mamy S. Visnovsky J. Hamrle J. Teillet A.R. Fert 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):43-49
Magnetite Fe3O4 films were grown on single crystal MgO (001) substrates using facing target sputtering technique. Conversion Electron M?ssbauer
Spectroscopy and magneto optical polar Kerr spectra have confirmed the stoichiometric repartition of Fe cations corresponding
to the inverse spinel structure and the electronic structure characteristic of bulk Fe3O4. Hysteresis loops carried out at room temperature show that, in a 1 T applied magnetic field, only 60% of the saturation
magnetization is detected. This behavior is discussed in correlation to the antiphase boundaries (APBs) observed by electron
microscopy. Magnetic force microscopy studies show that magnetic domains are larger than the mean distance between APBs.
Received 2 July 2001 相似文献
16.
Determination of the helium-4 mass in a Penning trap 总被引:2,自引:0,他引:2
S. Brunner T. Engel A. Schmitt G. Werth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(2):181-188
The determination of the rotational quadrupole alignment of diatomic molecules via REMPI detection is investigated. In this process a high focal intensity usually increases the detection probability. At high
intensities the AC Stark effect may cause a splitting of the normally degenerate mJ sublevels of a rotational state J beyond the spectral width of the exciting radiation. This leads to a selective detection of only certain mJ states with the consequence that deduced alignment factors can be misleading. From the theoretical considerations line profiles
are explicitly calculated for dynamic polarizabilities which represent the B
1Σ+
u←X
1Σ+
g transition of H2, in order to fit an experimental (3+1) REMPI spectrum and to predict (1+1') line shapes as a function of laser intensity.
It is further shown that the deduced quadrupole alignment factor
A
0
(2) is significantly changed by the second order AC Stark effect when the intensities are chosen high enough to observe asymmetric
broadened line profiles. Different combinations of relative linear polarizations of the exciting and ionizing laser beams
are discussed.
Received 1st August 2000 and Received in final form 2 May 2001 相似文献
17.
Monolayers of dioctadecyldimethylammonium bromide (DODA) at the air/water interface were used as model for charged surfaces
to study the adsorption of anionic polyelectrolytes. After spreading on a pure water surface the monolayers were compressed
and subsequently transferred onto a polyelectrolyte solution employing the Fromherz technique. The polyelectrolyte adsorption
was monitored by recording the changes in surface pressure at constant area. For poly(styrene sulfonate) and carboxymethylcellulose
the plot of the surface pressure as function of time gave curves which indicate a direct correlation between the adsorbed
amount and surface pressure as well as a solely diffusion controlled process. In the case of rigid rod-like poly(p-phenylene sulfonate)s the situation is more complicated. Plotting the surface pressure as function of time results in a curve
with sigmoidal shape, characterized by an induction period. The induction period can be explained by a domain formation, which
can be treated like a crystallization process. Employing the Avrami expression developed for polymer crystallization, the
change in the surface pressure upon adsorption of rigid rod-like poly(p-phenylene sulfonate)s can be described.
Received 1st July 2000 and Received in final form 7 December 2000 相似文献
18.
L.Y. Fong K.Y. Szeto 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(4):569-572
Data mining is performed using genetic algorithm on artificially generated time series data with short memory. The extraction
of rules from a training set and the subsequent testing of these rules provide a basis for the predictions on the test set.
The artificial time series are generated using the inverse whitening transformation, and the correlation function has an exponential
form with given time constant indicative of short memory. A vector quantization technique is employed to classify the daily
rate of return of this artificial time series into four categories. A simple genetic algorithm based on a fixed format of
rules is introduced to do the forecasting. Comparing to the benchmark tests with random walk and random guess, genetic algorithms
yield substantially better prediction rates, between 50% to 60%. This is an improvement compared with the 47% for random walk
prediction and 25% for random guessing method.
Received 29 August 2000 相似文献
19.
We develop a continuum theory of linear viscoelastic response in oriented monodomain nematic elastomers. The expression for
the dissipation function is analogous to the Leslie-Ericksen version of anisotropic nematic viscosity; we propose the relations
between the anisotropic rubber moduli and new viscous coefficients. A new dimensionless number is introduced, which describes
the relative magnitude of viscous and rubber-elastic torques. In an elastic medium with an independently mobile internal degree
of freedom, the nematic director with its own relaxation dynamics, the model shows a dramatic decrease in the dynamic modulus
in certain deformation geometries. The degree to which the storage modulus does not altogether drop to zero is shown to be
both dependent on frequency and to be proportional to the semi-softness, the non-ideality of a nematic network. We consider
the most interesting geometry for the implementation of the theory, calculating the dynamic response to an imposed simple
shear and making predictions for effective moduli and (exceptionally high) loss factors.
Received 16 October 2000 and Received in final form 10 December 2000 相似文献
20.
G. Perna V. Capozzi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):401-406
CdSe and CdS films, deposited on a sapphire substrate by means of pulsed laser ablation technique, have been investigated
by means of reflectivity and photoluminescence measurements in order to study the effect of such a transparent substrate on
the optical properties of the deposited epilayers. The reflectivity spectra at low temperature have been studied by means
of an analytical model which permits one to obtain the energies of the excitonic resonances. The photoluminescence spectra
show that our CdSe and CdS films present excitonic emission at low temperature, differently from the same films deposited
on quartz. The temperature dependence of the excitonic energy has been analysed by taking into account the contribution of
both the thermal expansion and electron-phonon interaction. The exciton linewidth has been analysed according to well known
phenomenological models.
Received 21 June 2001 and Received in final form 18 November 2001 相似文献