1,121 research outputs found
Self-consistent approach for the quantum confined Stark effect in shallow quantum wells
A computationally efficient, self-consistent complex scaling approach to
calculating characteristics of excitons in an external electric field in
quantum wells is introduced. The method allows one to extract the resonance
position as well as the field-induced broadening for the exciton resonance. For
the case of strong confinement the trial function is represented in factorized
form. The corresponding coupled self-consistent equations, which include the
effective complex potentials, are obtained. The method is applied to the
shallow quantum well. It is shown that in this case the real part of the
effective exciton potential is insensitive to changes of external electric
field up to the ionization threshold, while the imaginary part has
non-analytical field dependence and small for moderate electric fields. This
allows one to express the exciton quasi-energy at some field through the
renormalized expression for the zero-field bound state.Comment: 13 pages, RevTeX4, 6 figure
Excitation of the electric pygmy dipole resonance by inelastic electron scattering
To complete earlier studies of the properties of the electric pygmy dipole
resonance (PDR) obtained in various nuclear reactions, the excitation of the
1 states in Ce by scattering for momentum transfers
~fm is calculated within the plane-wave and distorted-wave
Born approximations. The excited states of the nucleus are described within the
Quasiparticle Random Phase Approximation (QRPA), but also within the
Quasiparticle-Phonon Model (QPM) by accounting for the coupling to complex
configurations. It is demonstrated that the excitation mechanism of the PDR
states in reactions is predominantly of transversal nature for
scattering angles . Being thus mediated by the
convection and spin nuclear currents, the like the
reaction, may provide additional information to the one obtained from Coulomb-
and hadronic excitations of the PDR in , , and
heavy-ion scattering reactions. The calculations predict that the
cross sections for the strongest individual PDR states are in general about
three orders of magnitude smaller as compared to the one of the lowest
state for the studied kinematics, but that they may become dominant at extreme
backward angles.Comment: Prepared for the special issue of EPJA on the topic "Giant, Pygmy,
Pairing Resonances and related topics" dedicated to the memory of Pier
Francesco Bortigno
Calculations of exchange interaction in impurity band of two-dimensional semiconductors with out of plane impurities
We calculate the singlet-triplet splitting for a couple of two-dimensional
electrons in the potential of two positively charged impurities which are
located out of plane. We consider different relations between vertical
distances of impurities and and their lateral distance . Such a
system has never been studied in atomic physics but the methods, worked out for
regular two-atomic molecules and helium atom, have been found to be useful.
Analytical expressions for several different limiting configurations of
impurities are obtained an interpolated formula for intermediate range of
parameters is proposed. The -dependence of the splitting is shown to become
weaker with increasing .Comment: 14 pages, RevTeX, 5 figures. Submitted to Phys Rev.
Angular distributions of scattered excited muonic hydrogen atoms
Differential cross sections of the Coulomb deexcitation in the collisions of
excited muonic hydrogen with the hydrogen atom have been studied for the first
time. In the framework of the fully quantum-mechanical close-coupling approach
both the differential cross sections for the transitions and
-averaged differential cross sections have been calculated for exotic atom
in the initial states with the principle quantum number at relative
motion energies eV and at scattering angles
. The vacuum polarization shifts of the
-states are taken into account. The calculated in the same approach
differential cross sections of the elastic and Stark scattering are also
presented. The main features of the calculated differential cross sections are
discussed and a strong anisotropy of cross sections for the Coulomb
deexcitation is predicted.Comment: 5 pages, 9 figure
Anharmonic properties of double giant dipole resonance
A systematic microscopic study of the anharmonic properties of the double
giant dipole resonance (DGDR) has been carried out, for the first time, for
nuclei with mass number spanning the whole mass table. It is concluded that
the corrections of the energy centroid of the and
components of the DGDR from its harmonic limit are negative, have a value of
the order of few hundred keV and follow an dependence.Comment: 4 pages, 2 figure
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