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1.
Cluzeau P Bonnand V Joly G Dolganov V Nguyen HT 《The European physical journal. E, Soft matter》2003,10(3):231-240
The behaviour of freely suspended smectic-C* ( SmC*) films at the bulk SmC*-cholesteric ( N*) phase transition has been investigated using polarized-reflected-light microscopy. Our experimental observations show that
above the bulk SmC*- N* phase transition the N* order appears in different ways according to the film thickness. In thin films, the conventional layer-by-layer thinning
occurs. In films of intermediate thickness N* inclusions nucleate inside the SmC* film. The distortions of the in-plane orientational order of the SmC* host phase induce elastic interactions between the inclusions and lead to their self-organization in chain-like structures.
Both the dynamic of the chaining and the parameters driving the equilibrium distance between the inclusions in the chain are
investigated. In thick films, N* fingers grow inside the film. The influence of the experimental conditions on the various processes is analysed.
Received 1 July 2002 / Published online: 15 April 2003
RID="a"
ID="a"e-mail: Philippe.cluzeau@univ-lille1.fr 相似文献
2.
E. Holmlund M. Kortelainen T. S. Kosmas J. Suhonen J. Toivanen 《Physics of Atomic Nuclei》2004,67(6):1198-1201
The low-energy structure of the dark-matter detector nuclei 71Ga, 73Ge, and 127I has been studied by using the microscopic quasiparticle-phonon model. The resulting ground states have been used to calculate theoretical predictions for detection rates of the lightest supersymmetric particle (LSP) in experiments studying elastic scattering of an LSP from an atomic nucleus. The highest rate, approximately 0.27 yr?1kg?1, among all the adopted SUSY parameters and renormalization schemes was provided by 127I at the zero limit of the detector energy threshold. 相似文献
3.
A resonance structure of the charge-exchange strength function S(E) and its effect on the neutrino-capture cross sections for the isotopes 71Ga, 98Mo, and 127I are studied within the self-consistent theory of finite Fermi systems. The calculation of the strength function S(E) takes into account Gamow–Teller, analog, and so-called lower lying pygmy resonances. The neutrino-capture cross sections σ(E) for the above three isotopes are calculated with allowance for the resonance structure of the strength function S(E), and the effect of each resonance on the energy dependence σ(E) is analyzed. It is found that all charge-exchange resonances in the strength function S(E) should be taken into account in calculating the neutrino-capture cross section σ(E) for the isotopes 71Ga, 98Mo, and 127I. The disregard of even highlying resonances leads to a substantial underestimation of the cross section σ(E), and this may affect the interpretation of respective experimental data. 相似文献
4.
Temperature dependencies of 27Al and 23Na nuclear magnetic resonance spectra and spin–lattice relaxations in mordenite have been studied in static and magic angle spinning regimes. Our data show that the spin–lattice relaxations of the 23Na and 27Al nuclei are mainly governed by interaction of nuclear quadrupole moments with electric field gradients of the crystal, modulated by translational motion of water molecules in the mordenite channels. At temperatures below 200 K, the dipolar interaction of nuclear spins with paramagnetic impurities becomes an important relaxation mechanism of the 23Na and 27Al nuclei. 相似文献
5.
E. Salas R. J. Jiménez-Riobóo A. de Andrés C. Prieto 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):151-155
Carbon thin films have been deposited by DC magnetron sputtering at different substrate temperatures ranging from 200 K to
400 K. The influence of the preparation substrate temperature on the elastic properties has been evidenced by means of the
High Resolution Brillouin Spectroscopy. Thus, the surface acoustic wave (SAW) velocity evolution could be assessed for the
different samples. The observed variation is analysed in terms of the relative population of sp2 allotropes phases forming the film. 相似文献
6.
D. G. Kellerman N. A. Zhuravlev A. S. Semenova I. R. Shein M. V. Kuznetsov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1157-1159
Li0.48Na0.35CoO2 lithium-sodium cobaltite was studied by means of wide-line 23Na and 7Li NMR. A series of quantum-chemical calculations allowed to us determine the optimum positions of Li and Na atoms, to construct
a map of the densities of electronic states near the Fermi level, and to estimate the electric field gradient on the Na nuclei.
The results from these calculations are compared with experimental data from NMR and X-ray photoelectron spectroscopy 相似文献
7.
M. R. Rowles J. V. Hanna K. J. Pike M. E. Smith B. H. O'Connor 《Applied magnetic resonance》2007,32(4):663-689
29Si, 27Al, 1H and 23Na solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) has been used to relate nominal composition, bonding
character and compressive strength properties in aluminosilicate inorganic polymers (AIPs). The 29Si chemical shift varies systematically with Si-to-Al ratio, indicating that the immediate structural environment of Si is
altering with nominal composition. Fast 1H MAS and 29Si T
SiH/T
1ρ relaxation measurements demonstrated that occluded pore H2O mobility within the disordered cavities is slow in comparison with H2O mobility characteristics observed within the ordered channel structures of zeolites. The 27Al MAS NMR data show that the Al coordination remains predominantly 4-coordinate. In comparison with the 29Si MAS data, the corresponding 27Al MAS line shapes are relatively narrow, suggesting that the AlO4 tetrahedral geometry is largely unperturbed and the dominant source of structural disorder is propagated by large distributions
of Si–O bond angles and bond lengths. Corresponding 23Na MAS and multiple-quantum MAS NMR data indicate that Na speciation is dominated by distributions of hydration states; however,
more highly resolved 23Na resonances observed in some preparations supported the existence of short-range order. New structural elements are proposed
to account for the existence of these Na resonances and an improved model for the structure of AIPs has also been proposed.
Authors' address: John V. Hanna, NMR Facility, Institute of Materials and Engineering Science, Lucas Heights Research Laboratories,
Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234, Australia 相似文献
8.
Zhang XiaoAn Xiao GuoQing Yang ZhiHu Chen XiMeng Zhao YongTao Li FuLi Wang Li Cui Ying Zhang HongQiang Zhan WenLong 《中国科学G辑(英文版)》2008,51(1):82-89
Using the slow highly charged ions 129Xe
q+ (q = 25, 26, 27; initial kinetic T
0⩽4.65 keV/a.u.) to impact Au surface, the Au atomic Mα characteristic X-ray spectrum is induced. The result shows that as
long as the charge state of projectile is high enough, the heavy atomic characteristic X-ray can be effectively excited even
though the incident beam is very weak (nA magnitude), and the X-ray yield per ion is in the order of 10−8 and increases with the kinetic energy and potential energy of projectile. By measuring the Au Mα-X-ray spectra, Au atomic
N-level lifetime is estimated at about 1.33×10−18 s based on Heisenberg uncertainty relation.
Supported by the National Natural Science Foundation of China (Grant Nos. 10574132, 10274088 and 10405025), the Talent Introduction
Project of Xianyang Normal University (Grant No. 05XSYK103) and the Education Commission Foundation of Shaanxi Province (Grant
No. 04JK300) 相似文献
9.
Density functional theory together with statistical thermodynamics based on the equilibrium constants method and concept of
orientational entropy were applied to reproduce the temperature dependences of 1H and 17O nuclear magnetic resonance (NMR) chemical shifts in liquid water. Despite a rather simple theoretical model, a satisfactory
agreement between calculated NMR quantities and corresponding experimental data was found. By using only a single adjustable
parameter of arbitrary directionality, we succeeded to imitate the first-order temperature effect for both (1H and 17O) NMR signals in the neat water. 1H and 17O magnetic shielding tensors of water molecules in various water clusters have been calculated using the density functional
theory. The full geometry optimization was performed using Becke's three-parameter hybrid method and the Lee–Yang–Parr correlation
functional (B3LYP) combined with 6-311++G** basis set. Magnetic shielding tensors have been calculated using the modified hybrid functional of Perdew, Burke and Ernzerhof,
and the gauge-including atomic orbital approach was applied to ensure gauge invariance of the results. Solvent effects were
taken into account by the polarized continuum model.
Authors' address: Vytautas Balevicius, Faculty of Physics, Vilnius University, Sauletekio 9, Vilnius 10222, Lithuania 相似文献
10.
W. P. Halperin D. T. Sprague T. M. Haard J. B. Kycia Y. Lee M. R. Rand 《Czechoslovak Journal of Physics》1996,46(6):2989-2994
The transition to superfluidity of3He in high porosity (98.2%) acrogel has been observed by nuclear magnetic resonance techniques. The onset of the transition at all pressures above 13 bar is marked by a sharp increase in NMR frequency similar to that observed in bulk3He-A. This suggests that the aerogel/superfluid phase is highly homogeneous although both the transition temperature, Tc, and the amplitude of the order parameter are substantially suppressed. The acrogel strands are ≈ 50Å in diameter, much smaller than the superfluid coherence length. Consequently, we have attempted to interpret our observations as an impurity scattering problem. Based on our measurements of the magnetic field dependence of Tc it appears that both magnetic and potential scattering play important roles where the magnetic scattering can be associated with solid3He on the aerogel surface. This is determined by isotopic exchange with4He, a process which appears to stabilize a new superfluid state similar to the bulk B-phase. 相似文献
11.
Deuterofullerites C60Dx have been studied by 2H and 13C NMR. These fullerites have two types of carbon–deuterium bonds: C–D terminal bonds, characterized by the quadrupole coupling constant (QCC) of 171 kHz, and –C ··· D ··· C– bridging bonds with a QCC of 56 kHz. The latter is responsible for the rigid lattice found in these fullerites, which is untypical of fullerenes. PACS 81.05.Tp; 82.56.Fk; 61.48.+c; 61.18.Fs; 61.10.Nz 相似文献
12.
A. Merli F. Sauer L. Wöste A. Lindinger 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):217-220
We report on isotope selective three-photon ionization of
two isotopomers of KRb by applying evolution strategies. The
particularity of this experiment is based on the high resolution
phase and amplitude modulation of the fs-laser pulses provided by a
2 × 640 pixel pulse shaper. The optimization in a closed feedback
loop performed with spectrally broad pulses centered at 840 nm shows
high enhancements of one isotopomer at the expense of the other
isotopomer and vice versa. From the optimal laser field we aim to
gain details about the selective ionization sequence and the
wavepacket evolution on the involved vibrational states. 相似文献
13.
D. Pérez Sánchez A. Martin Sánchez M. Jurado Vargas 《Czechoslovak Journal of Physics》2003,53(1):A25-A30
A simple radiochemical procedure has been developed to determine 210Pb and 210Po in environmental samples from the same matrix. Sediment samples are decomposed by leaching with mineral acids or by microwave digestion, while water samples are pre-concentrated. One part of the resulting solution, spiked with 209Po, is used for 210Po determination by spontaneous deposition onto nickel disks (α-spectrometry). The other part is assayed for 210Pb, separating the Pb either by anion-exchange (sediment samples), or by solvent extraction (water samples). The 210Pb source is finally prepared by precipitation as oxalate and the chemical recovery determined by gravimetry. The 210Pb activity concentration is determined by liquid scintillation. A standard sediment sample supplied by IAEA and spiked water samples were analysed to check the procedure. The 210Pb and 210Po measurements agreed well with the certifications, deviations being less than 10%. The mean recoveries for Pb and Po were (70±12)% and (77±8%) for sediments, and (70±10)% and (81±7)% for waters, respectively. 相似文献
14.
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
15.
M. A. Cardona B. Roussière J. Libert J. Genevey J. Sauvage the ISOCELE ISOLDE Collaborations 《The European Physical Journal A - Hadrons and Nuclei》2007,31(2):141-154
Excited states in 182Os were populated by the β+/EC decay of 182Ir following mass separation. Gamma-ray and conversion electron spectroscopy techniques were employed. Monopole (E0) contributions were determined in transitions populating the ground-state band. A systematic study of the low-spin structures
in the Os isotopes is presented and a detailed analysis in the framework of a microscopic configuration mixing approach is
performed. 相似文献
16.
T. Grahn J. Pakarinen L. Jokiniemi M. Albers K. Auranen C. Bauer C. Bernards A. Blazhev P. A. Butler S. Bönig A. Damyanova T. De Coster H. De Witte J. Elseviers L. P. Gaffney M. Huyse A. Herzáň U. Jakobsson R. Julin N. Kesteloot J. Konki Th. Kröll L. Lewandowski K. Moschner P. Peura M. Pfeiffer D. Radeck P. Rahkila E. Rapisarda P. Reiter K. Reynders M. Rudiger M. -D. Salsac S. Sambi M. Scheck M. Seidlitz B. Siebeck T. Steinbach S. Stolze J. Suhonen P. Thoele M. Thürauf N. Warr P. Van Duppen M. Venhart M. J. Vermeulen V. Werner M. Veselsky A. Vogt K. Wrzosek-Lipska M. Zielińska 《The European Physical Journal A - Hadrons and Nuclei》2016,52(11):340
17.
A. G. Smol’nikov V. V. Ogloblichev S. V. Verkhovskii K. N. Mikhalev A. Yu. Yakubovskii K. Kumagai Y. Furukawa A. F. Sadykov Yu. V. Piskunov A. P. Gerashchenko S. N. Barilo S. V. Shiryaev 《JETP Letters》2015,102(10):674-677
The magnetically ordered phase of the CuCrO2 single crystal has been studied by the nuclear magnetic resonance (NMR) method on 53Cr nuclei in the absence of an external magnetic field. The 53Cr NMR spectrum is observed in the frequency range νres = 61–66 MHz. The shape of the spectrum depends on the delay tdel between pulses in the pulse sequence τπ/2–t del–τπ–t del–echo. The spin–spin and spin–lattice relaxation times have been measured. Components of the electric field gradient, hyperfine fields, and the magnetic moment on chromium atoms have been estimated. 相似文献
18.
The effects of the 57Fe isotope content and high-frequency magnetic field amplitude h
1 on the shape of the NMR spectrum of multiferroic BiFeO3 at T = 4.2 K are studied by pulsed nuclear magnetic resonance. The NMR spectrum shape and transverse relaxation time T
2 are found to depend strongly on the 57Fe isotope content and h
1 in multiferroic BiFeO3 in the presence of a spatial spin-modulated structure of a cycloid type. In a sample with a high 57Fe isotope content, the Suhl-Nakamura interaction contributes substantially to T
2. When these dynamic effects are taken into account for analysis of the NMR spectrum shape, an undisturbed (without an anharmonicity
effect) spatial spin-modulated structure of a cycloid type is shown to exist in BiFeO3. 相似文献
19.
V. L. Matukhin V. L. Ermakov O. I. Gnezdilov E. V. Shmidt A. N. Safonov T. G. Aminov G. G. Shabunina 《Russian Physics Journal》2009,52(8):785-788
The synthesized base compound CuGaTe2 and the Mn-doped compounds Cu0.97Ga0.97Mn0.06Te2 and Cu0.93Ga0.93Mn0.14Te2 have been investigated by using 63Cu and 69Ga NMR spectroscopy. The NMR spectra obtained testify to substantial structural distortions near the cationic positions in
the crystal lattice of Mndoped samples. The constants of quadrupole coupling between 63Cu and 69Ga nuclei in the compounds investigated have been estimated. 相似文献
20.
M. A. Naumenko V. V. Samarin Yu. E. Penionzhkevich N. K. Skobelev 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(6):710-716
Experimental cross sections of formation of isotopes 46Sc (in reaction 6He + 45Sc), 196,198Au (in reaction 6He + 197Au), and 65Zn (in reaction 6He + 64Zn) are analyzed. The time-dependent Schrödinger equation for the outer neutrons of 6He and 197Au nuclei is solved numerically to calculate the probability of neutron transfer and transfer cross sections. In reaction 6He + 197Au, the contribution of fusion and subsequent evaporation to experimental data can be neglected, while the corresponding contributions to reactions 6He + 45Sc and 6He + 64Zn are considerable. Fusion–evaporation is taken into account using the computational code of the NRV knowledge base. The results of calculations are in satisfactory agreement with the experimental data. 相似文献