4,339 research outputs found
Improved photoionization mass spectrometer
Improved spectrometer for gas analysis lessens the intensity problem that occurs in obtaining dispersed ultraviolet radiation. A filter, consisting of a selectively transmitting gas cell, a thin film or mirror, or a predispersing grating, alleviates problems of interference from higher-order spectral lines and from scattered ultraviolet light
Analytical photoionization mass spectrometer with an argon gas filter between the light source and monochrometer Patent
Analytical photoionization mass spectrometer with argon gas filter between light source and monochromete
Unconventional pairing in bipolaronic theories
Various mechanisms have been put forward for cuprate superconductivity, which
fit largely into two camps: spin-fluctuation and electron-phonon (el-ph)
mechanisms. However, in spite of a large effort, electron-phonon interactions
are not fully understood away from clearly defined limits. To this end, we use
a numerically exact algorithm to simulate the binding of bipolarons. We present
the results of a continuous-time quantum Monte-Carlo (CTQMC) algorithm on a
tight-binding lattice, for bipolarons with arbitrary interaction range in the
presence of strong coulomb repulsion. The algorithm is sufficiently efficient
that we can discuss properties of bipolarons with various pairing symmetries.
We investigate the effective mass and binding energies of singlet and triplet
real-space bipolarons for the first time, and discuss the extensions necessary
to investigate -symmetric pairs.Comment: Submitted to M2S-HTSC VIII, Dresden 2006, 2 page
Effects of lattice geometry and interaction range on polaron dynamics
We study the effects of lattice type on polaron dynamics using a
continuous-time quantum Monte-Carlo approach. Holstein and screened Froehlich
polarons are simulated on a number of different Bravais lattices. The effective
mass, isotope coefficients, ground state energy and energy spectra, phonon
numbers, and density of states are calculated. In addition, the results are
compared with weak and strong coupling perturbation theory. For the Holstein
polaron, it is found that the crossover between weak and strong coupling
results becomes sharper as the coordination number is increased. In higher
dimensions, polarons are much less mobile at strong coupling, with more phonons
contributing to the polaron. The total energy decreases monotonically with
coupling. Spectral properties of the polaron depend on the lattice type
considered, with the dimensionality contributing to the shape and the
coordination number to the bandwidth. As the range of the electron-phonon
interaction is increased, the coordination number becomes less important, with
the dimensionality taking the leading role.Comment: 16 pages, 12 figure
Absolute photoionization cross sections of atomic oxygen
The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states
Kinetic energies of fragment ions produced by dissociative photoionization of NO
The kinetic energies of ions produced by dissociative photoionization of NO have been measured at the discrete resonance lines of He (584A) and Ne (736A), and with undispersed synchrotron radiation. O sup + ions were identified with energies from 0 to approximately 0.5 eV and two groups of N sup + ions one with energy of 0.36 eV and another with energies between 0.9 and 1.5 eV, apparently produced by predissociation of the C sup 3 P 1 and B'1 sigma states respectively
Charged Higgs bosons from the 3-3-1 models and the anomalies
Several anomalies in the semileptonic B-meson decays such as
have been reported by , Belle, and LHCb
collaborations recently. In this paper, we investigate the contributions of the
charged Higgs bosons from the 3-3-1 models to the
anomalies. We find that, in a wide range of parameter space, the 3-3-1 models
might give reasonable explanations to the anomalies and
other analogous anomalies of the B meson's semileptonic decays.Comment: Accpeted by Physical Review
Tunable refraction in a two dimensional quantum metamaterial
In this paper we consider a two-dimensional metamaterial comprising an array
of qubits (two level quantum objects). Here we show that a two-dimensional
quantum metamaterial may be controlled, e.g. via the application of a magnetic
flux, so as to provide controllable refraction of an input signal. Our results
are consistent with a material that could be quantum birefringent (beam
splitter) or not dependent on the application of this control parameter. We
note that quantum metamaterials as proposed here may be fabricated from a
variety of current candidate technologies from superconducting qubits to
quantum dots. Thus the ideas proposed in this work would be readily testable in
existing state of the art laboratories.Comment: 4 pages, 2 figure
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