11,533 research outputs found
Interface properties in dielectrics: A cross-section analysis by atomic force microscopy
International audienceEven if interfaces are more and more investigated their properties remain partially unknown, especially as regards their electronic properties. This is mainly related to the lack of characterization at relevant scale. In this context, electrical modes derivate from Atomic Force Microscopy appear well adapted. In this paper, a method to probe space charge at nanoscale is proposed. This method is based on surface potential measurement by Kelvin Probe Force Microscopy (KPFM) and post-processing technique based either on numerical derivation or Finite Element Method. Through these methods, densities of interface charges and injected charges were determined at different metal/dielectric interfaces
Synchronous Behavior of Two Coupled Electronic Neurons
We report on experimental studies of synchronization phenomena in a pair of
analog electronic neurons (ENs). The ENs were designed to reproduce the
observed membrane voltage oscillations of isolated biological neurons from the
stomatogastric ganglion of the California spiny lobster Panulirus interruptus.
The ENs are simple analog circuits which integrate four dimensional
differential equations representing fast and slow subcellular mechanisms that
produce the characteristic regular/chaotic spiking-bursting behavior of these
cells. In this paper we study their dynamical behavior as we couple them in the
same configurations as we have done for their counterpart biological neurons.
The interconnections we use for these neural oscillators are both direct
electrical connections and excitatory and inhibitory chemical connections: each
realized by analog circuitry and suggested by biological examples. We provide
here quantitative evidence that the ENs and the biological neurons behave
similarly when coupled in the same manner. They each display well defined
bifurcations in their mutual synchronization and regularization. We report
briefly on an experiment on coupled biological neurons and four dimensional ENs
which provides further ground for testing the validity of our numerical and
electronic models of individual neural behavior. Our experiments as a whole
present interesting new examples of regularization and synchronization in
coupled nonlinear oscillators.Comment: 26 pages, 10 figure
Mapping of shape invariant potentials by the point canonical transformation
In this paper by using the method of point canonical transformation we find
that the Coulomb and Kratzer potentials can be mapped to the Morse potential.
Then we show that the P\"{o}schl-Teller potential type I belongs to the same
subclass of shape invariant potentials as Hulth\'{e}n potential. Also we show
that the shape-invariant algebra for Coulomb, Kratzer, and Morse potentials is
SU(1,1), while the shape-invariant algebra for P\"{o}schl-Teller type I and
Hulth\'{e}n is SU(2)
Mesoscopic molecular ions in Bose-Einstein condensates
We study the possible formation of large (mesoscopic) molecular ions in an
ultracold degenerate bosonic gas doped with charged particles (ions). We show
that the polarization potentials produced by the ionic impurities are capable
of capturing hundreds of atoms into loosely bound states. We describe the
spontaneous formation of these hollow molecular ions via phonon emission and
suggest an optical technique for coherent stimulated transitions of free atoms
into a specific bound state. These results open up new interesting
possibilities for manipulating tightly confined ensembles.Comment: 4 pages (two-columns), 2 figure
Fourier transform spectroscopy and coupled-channel deperturbation treatment of the A1Sigma+ ~ b3Pi complex of KCs molecule
The laser induced fluorescence (LIF) spectra A1Sigma ~ b3Pi --> X1Sigma+ of
KCs dimer were recorded in near infrared region by Fourier Transform
Spectrometer with a resolution of 0.03 cm-1. Overall more than 200 LIF spectra
were rotationally assigned to 39K133Cs and 41K133Cs isotopomers yielding with
the uncertainty of 0.003-0.01 cm-1 more than 3400 rovibronic term values of the
strongly mixed singlet A1Sigma+ and triplet b3Pi states. Experimental data
massive starts from the lowest vibrational level v_A=0 of the singlet and
nonuniformly cover the energy range from 10040 to 13250 cm-1 with rotational
quantum numbers J from 7 to 225. Besides of the dominating regular A1Sigma+ ~
b3P Omega=0 interactions the weak and local heterogenous A1S+ ~ b3P Omega=1
perturbations have been discovered and analyzed. Coupled-channel deperturbation
analysis of the experimental 39K133Cs e-parity termvalues of the A1S+ ~ b3P
complex was accomplished in the framework of the phenomenological 4 x 4
Hamiltonian accounting implicitly for regular interactions with the remote
states manifold. The resulting diabatic potential energy curves of the
interacting states and relevant spin-orbit coupling matrix elements defined
analytically by Expanded Morse Oscillators model reproduce 95% of experimental
data field of the 39K133Cs isotopomer with a standard deviation of 0.004 cm-1
which is consistent with the uncertainty of the experiment. Reliability of the
derived parameters was additionally confirmed by a good agreement between the
predicted and experimental termvalues of 41K133Cs isotopomer. Calculated
intensity distributions in the A ~ b --> X LIF progressions are also consistent
with their experimental counterparts.Comment: 17 pages, 14 figure
Percolation model for structural phase transitions in LiHIO mixed crystals
A percolation model is proposed to explain the structural phase transitions
found in LiHIO mixed crystals as a function of the
concentration parameter . The percolation thresholds are obtained from Monte
Carlo simulations on the specific lattices occupied by lithium atoms and
hydrogen bonds. The theoretical results strongly suggest that percolating
lithium vacancies and hydrogen bonds are indeed responsible for the solid
solution observed in the experimental range .Comment: 4 pages, 2 figure
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