8,794 research outputs found
A hydrogenic molecular atmosphere of a neutron star
A model of a hydrogenic content of atmosphere of the isolated neutron star
1E1207.4-5209 is proposed. It is based on the assumption that the main
component in the atmosphere is the exotic molecular ion and that
there exists a magnetic field in the range of G.
Photoionization H_3^{2+} \rar e + 3p and photodissociation H_3^{2+} \rar H +
2p correspond to two absorption features at 0.7 KeV and 1.4 KeV, respectively,
discovered by {\it Chandra} observatory (Sanwal et al, 2002). The model
predicts one more absorption feature at 80-150 eV corresponding to
photodissociation H_3^{2+} \rar H_2^+ + p.Comment: 8 pages, 1 figur
Weak antilocalization in a 2D electron gas with the chiral splitting of the spectrum
Motivated by the recent observation of the metal-insulator transition in
Si-MOSFETs we consider the quantum interference correction to the conductivity
in the presence of the Rashba spin splitting. For a small splitting, a
crossover from the localizing to antilocalizing regime is obtained. The
symplectic correction is revealed in the limit of a large separation between
the chiral branches. The relevance of the chiral splitting for the 2D electron
gas in Si-MOSFETs is discussed.Comment: 7 pages, REVTeX. Mistake corrected; in the limit of a large chiral
splitting the correction to the conductivity does not vanish but approaches
the symplectic valu
Exchange and correlation energies of ground states of atoms and molecules in strong magnetic fields
Using a Hartree-Fock mesh method and a configuration interaction approach
based on a generalized Gaussian basis set we investigate the behaviour of the
exchange and correlation energies of small atoms and molecules, namely th e
helium and lithium atom as well as the hydrogen molecule, in the presence of a
magnetic field covering the regime B=0-100a.u. In general the importance of the
exchange energy to the binding properties of at oms or molecules increases
strongly with increasing field strength. This is due to the spin-flip
transitions and in particular due to the contributions of the tightly bound
hydrogenic state s which are involved in the corresponding ground states of
different symmetries. In contrast to the exchange energy the correlation energy
becomes less relevant with increasing field strength. This holds for the
individual configurations constituting the ground state and for the crossovers
of the global ground state.Comment: 4 Figures acc.f.publ.in Phys.Rev.
Quantum conductivity corrections in two dimensional long-range disordered systems with strong spin-orbit splitting of electron spectrum
We study quantum corrections to conductivity in a 2D system with a smooth
random potential and strong spin-orbit splitting of the spectrum. We show that
the interference correction is positive and down to the very low temperature
can exceed the negative correction related to electron-electron interactions.
We discuss this result in the context of the problem of the metal-insulator
transition in Si-MOSFET structures.Comment: 8 pages, no figure
Apparent Metallic Behavior at B = 0 of a two-dimensional electron system in AlAs
We report the observation of metallic-like behavior at low temperatures and
zero magnetic field in two dimensional (2D) electrons in an AlAs quantum well.
At high densities the resistance of the sample decreases with decreasing
temperature, but as the density is reduced the behavior changes to insulating,
with the resistance increasing as the temperature is decreased. The effect is
similar to that observed in 2D electrons in Si-MOSFETs, and in 2D holes in SiGe
and GaAs, and points to the generality of this phenomenon
Analysis of Approaches to the Assessment of Innovative Development of Economic System in the Region
In the article the structure of regional innovative system is investigated and its conceptual model opening an essence of innovative activity is developed. The system of the indicators allowing to estimate the level of innovative development of regional economies is offered and the directions regarding improvement of the operating assessment techniques are designated. The author’s structure of the index of innovative development of regions consisting of four subindexes reflecting a condition of regional innovative system is offered; it is shown that assessment of regional economic systems with use of author’s approach allows to keep track of dynamics of development of regional innovative systems for development of organizational and administrative decisions on increase in their efficiency
Problems of High-quality Doped Y2O3-ceramics Fabrication
Tm:Y2O3 , Ho:Y2O3 and Yb:Y2O3 ceramic samples were fabricated using different heat treatments modes. La2O3 (0.5 mol.%) and ZrO2 (1.5 mol.%) were used as sintering additives. Based on the investigation of structural properties of obtained samples, annealing mode was adjusted, and another set of samples with better optical quality was fabricated. In-line transmittance of the latter samples is 70% at 400nm and 75.6% at 600nm.
Keywords: Y2O3 , laser ceramic
Effect of Tilted Magnetic Field on the Anomalous H=0 Conducting Phase in High-Mobility Si MOSFETs
The suppression by a magnetic field of the anomalous H=0 conducting phase in
high-mobility silicon MOSFETs is independent of the angle between the field and
the plane of the 2D electron system. In the presence of a parallel field large
enough to fully quench the anomalous conducting phase, the behavior is similar
to that of disordered GaAs/AlGaAs heterostructures: the system is insulating in
zero (perpendicular) field and exhibits reentrant insulator-quantum Hall
effect-insulator transitions as a function of perpendicular field. The results
demonstrate that the suppression of the low-T phase is related only to the
electrons' spin.Comment: 4 pages, including 3 figures. We corrected several typos in the
figures and caption
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