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1.
The segmental ordering within a lamellar polystyrene-polydimethylsiloxane diblock (PS-PDMS) was examined by NMR. A non-uniform
stretching of the PDMS chains was evidenced. Although chain segments displaying isotropic reorientational motions are present
along the chains, relaxation measurements on the free PDMS extremities demonstrate that these latter are oriented and submitted
to a non-zero constraint. This specific result allows to precise some features of the order distribution within the lamellae.
Received: 27 March 2003 / Accepted: 9 May 2003 / Published online: 4 June 2003
RID="a"
ID="a"e-mail: deloche@lps.u-psud.fr 相似文献
2.
M. Nakamura R.-J. Tarento P. Joyes 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):169-172
Electron transfer in the collisions of a
with a Na is theoretically studied. It is assumed that the
target
is collinear (D
h
)
and that its electronic state is meta-stable triplet
state. Adiabatic potential energy surfaces and non-adiabatic
couplings of the
system are calculated by using a semi-empirical
diatomics-in-molecules (DIM) method. The positions of
(avoided)-crossings of potential surfaces are investigated and
the non-adiabatic couplings between two different electronic
states are calculated. An avoided crossing is found in the
region where the separation between the target and projectile is
relatively large (10–15 bohr). A dynamical calculation
demonstrates that this crossing causes charge transfer between
the target and projectile. Another intersection at a smaller
separation changes the targets spin state (from triplet state
to singlet state or vice
versa). The cross-sections for charge and spin
transfer reaction are estimated at the collision energy of 6.8
keV. It is found that the charge transfer cross-section is
extremely enhanced when the target cluster ion is in its
meta-stable triplet state comared to the case where the cluster
is the ground singlet state. 相似文献
3.
D. R. Justes A. W. Castleman Jr R. Mitri V. Bonai-Koutecký 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):331-334
Density functional calculations have been performed for
the
reactions towards ethylene considering atomic and molecular
oxygen loss, oxygen transfer and association reactions. The
oxygen transfer channel to ethylene is energetically favourable
in contrast to the oxygen loss. This is in agreement with the
experimental results [1] which show that
does not lose atomic oxygen during the collision induced
dissociation at thermal energies. A radical cation mechanism
based on structure-reactivity relation of
cluster is proposed to explain oxygen transfer channel
indicating that this reaction is size selective. 相似文献
4.
M. Giroud K. Hasselbach H. Courtois D. Mailly B. Pannetier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):103-109
We present electrical transport experiments performed on submicron hybrid devices made of a ferromagnetic conductor (Co) and
a superconducting (Al) electrode. The sample was patterned in order to separate the contributions of the Co conductor and
of the Co-Al interface. We observed a strong influence of the Al electrode superconductivity on the resistance of the Co conductor.
This effect is large only when the interface is highly transparent. We characterized the dependence of the observed resistance
decrease on temperature, bias current and magnetic field. As the differential resistance of the ferromagnet exhibits a non-trivial
asymmetry, we claim that the magnetic domain structure plays an important role in the electron transport properties of superconducting
/ ferromagnetic conductors.
Received 9 July 2002 / Received in final form 22 October 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: herve.courtois@grenoble.cnrs.fr
RID="b"
ID="b"associated to Université Joseph Fourier 相似文献
5.
Cluster models were used to represent the β-type cationic sites of the protonated beta zeolite (H-BEA) and the loading of PdO on these sites. The properties of these clusters and the cleavage of methane CH bond over these clusters were studied using density functional theory (DFT) method. The stability of H-BEA was enhanced due to the formation of hydrogen bonds. After PdO loading, the Pd atom bonds to four oxygen atoms among which three H-BEA framework oxygen atoms are included to form an approximate planar structure with Pd in the centre. This structure is very similar to that of bulk PdO. The acidic proton of H-BEA and the oxygen atom of PdO participate in the cleavage of methane CH bond, indicating that PdO is the active species for the activation of methane. Over the clusters constructed in the present work, the calculated energy barriers for the cleavage of methane CH bond are in the region between 17.54 and 21.02 kcal mol−1. 相似文献
6.
The propagation of light along the axis of non-homogeneity of a structurally chiral medium (SCM) under the influence of a low-frequency (dc) electric field aligned along the same axis is investigated. The Pockels effect is assumed to occur, and the SCM is taken to possess locally a point group symmetry. The frequency-domain Maxwell curl equations are cast in a 4 × 4 matrix representation, and the Oseen transformation is invoked. The band structure is analyzed, as are also the eigenvectors as well as the transfer matrix. Finally, the reflection and transmission of a plane wave due to a SCM of finite thickness is considered. The low-frequency electric field is shown to control the bandgap. 相似文献
7.
In the present work we studied the immediate medium response to the excitation to the
Rydberg state of NO impurity embedded in a solid Kr matrix. The excitation, extended over a large range of the lattice was investigated by classical molecular dynamics simulations. This has been done using Lennard-Jones pair potentials from the literature for the
interactions and fitted in this work for the
ones, since these last have not been reported in literature. Thus is obtained the first shell response to the excitation of the impurity (approximately the first 2 ps) as well as the response of the continuous shells up to the 10th one. This first response of the first shell is compared to that for similar systems (Ne and Ar matrixes doped with NO). Therefore some theoretical conclusions are drawn. The results indicate the inertial character of the response propagation throughout the surrounding medium and the high degree of nuclear coherence at short times.Received: 27 February 2003, Published online: 30 July 2003PACS:
34.30.+h Intramolecular energy transfer; intramolecular dynamics; dynamics of van der Waals molecules - 02.70.Ns Molecular dynamics and particle methods - 31.70.Ks Molecular solids 相似文献
8.
A.A. Zvyagin 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):351-360
The behavior of charge and spin persistent currents in an integrable lattice ring of strongly correlated electrons with a
magnetic impurity is exactly studied. Our results manifest that the oscillations of charge and spin persistent currents are
similar to the ones, earlier obtained for integrable continuum models with a magnetic impurity. The difference is due to two
(instead of one) Fermi velocities of low-lying excitations. The form of oscillations in the ground state is “saw-tooth”-like,
generic for any multi-particle coherent one-dimensional models. The integrable magnetic impurity introduces net charge and
spin chiralities in the generic integrable lattice system, which determine the initial phase shifts of charge and spin persistent
currents. We show that the magnitude of the charge persistent current in the generic Kondo situation does not depend on the
parameters of the magnetic impurity, unlike the (magneto)resistivity of transport currents.
Received 30 January 2003 / Received in final form 12 March 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: zvyagin@fy.chalmers.se 相似文献
9.
Equilibrium phase coexistence between two chemical species implies the equality of the chemical potentials and of the osmotic
pressures. We study this problem on a deformable membrane when one type of the molecules serves as anchor for polymeric chains
immersed in the surrounding medium (considered as a good solvent). We derive the general conditions for phase coexistence
when both the curvature of the membrane and the density field of the anchor molecule are free to adjust themselves. We show
that curvature favors phase segregation. Our model predicts that membranes decorated with polymeric chains exhibit new shape
bifurcations without equivalent in fixed density systems.
Received: 26 November 2002 / Accepted: 2 April 2003 / Published online: 12 May 2003
RID="a"
ID="a"e-mail: nicolas@drfmc.ceng.cea.fr
RID="b"
ID="b"e-mail: bfourcade@cea.fr 相似文献
10.
We present a quantum mechanical framework for defining the statistics of measurements of
, A(t) being a quantum mechanical variable. This is a generalization of the so-called full counting statistics proposed earlier for DC electric currents. We develop an influence functional formalism that allows us to study the quantum system along with the measuring device while fully accounting for the back action of the detector on the system to be measured. We define the full counting statistics of an arbitrary variable by means of an evolution operator that relates the initial and final density matrices of the measuring device. In this way we are able to resolve inconsistencies that occur in earlier definitions. We suggest two schemes to observe the so defined statistics experimentally.Received: 30 June 2003, Published online: 15 October 2003PACS:
73.50.Td Noise processes and phenomena - 73.23.-b Electronic transport in mesoscopic systems - 74.40.+k Fluctuations (noise, chaos, nonequilibrium superconductivity, localization, etc.) 相似文献