1,317 research outputs found
Positronium in intense laser fields
The dynamics and radiation of positronium is investigated in intense laser
fields.Comment: 13 pages, 3 figure
Semi-classical limitations for photon emission in strong external fields
The semi-classical heuristic emission formula of Baier-Katkov [Sov. Phys.
JETP \textbf{26}, 854 (1968)] is well-known to describe radiation of an
ultrarelativistic electron in strong external fields employing the electron's
classical trajectory. To find the limitations of the Baier-Katkov approach, we
investigate electron radiation in a strong rotating electric field quantum
mechanically using the Wentzel-Kramers-Brillouin approximation. Except for an
ultrarelativistic velocity, it is shown that an additional condition is
required in order to recover the widely used semi-classical result. A violation
of this condition leads to two consequences. First, it gives rise to
qualitative discrepancy in harmonic spectra between the two approaches. Second,
the quantum harmonic spectra are determined not only by the classical
trajectory but also by the dispersion relation of the effective photons of the
external field
QED calculation of the nuclear magnetic shielding for hydrogen-like ions
We report an ab initio calculation of the shielding of the nuclear magnetic
moment by the bound electron in hydrogen-like ions. This investigation takes
into account several effects that have not been calculated before (electron
self-energy, vacuum polarization, nuclear magnetization distribution), thus
bringing the theory to the point where further progress is impeded by the
uncertainty due to nuclear-structure effects. The QED corrections are
calculated to all orders in the nuclear binding strength parameter and,
independently, to the leading order in the expansion in this parameter. The
results obtained lay the ground for the high-precision determination of nuclear
magnetic dipole moments from measurements of the g-factor of hydrogen-like
ions
Microscopic laser-driven high-energy colliders
The concept of a laser-guided collider in the high-energy regime is
presented and its feasibility discussed. Ultra-intense laser pulses and strong
static magnetic fields are employed to unite in one stage the electron and
positron acceleration and their head-on-head collision. We show that the
resulting coherent collisions in the GeV regime yield an enormous enhancement
of the luminosity with regard to conventional incoherent colliders
Electron-correlation effects in the -factor of light Li-like ions
We investigate electron-correlation effects in the -factor of the ground
state of Li-like ions. Our calculations are performed within the
nonrelativistic quantum electrodynamics (NRQED) expansion up to two leading
orders in the fine-structure constant , and . The
dependence of the NRQED results on the nuclear charge number is studied and
the individual -expansion contributions are identified. Combining the
obtained data with the results of the all-order (in ) calculations
performed within the expansion, we derive the unified theoretical
predictions for the -factor of light Li-like ions.Comment: 9 pages, 4 table
QED theory of the nuclear magnetic shielding in hydrogen-like ions
The shielding of the nuclear magnetic moment by the bound electron in
hydrogen-like ions is calculated ab initio with inclusion of relativistic,
nuclear, and quantum electrodynamics (QED) effects. The QED correction is
evaluated to all orders in the nuclear binding strength parameter and,
independently, to the first order in the expansion in this parameter. The
results obtained lay the basis for the high-precision determination of nuclear
magnetic dipole moments from measurements of the g-factor of hydrogen-like
ions.Comment: 4 pages, 2 tables, 2 figure
Polarization operator approach to electron-positron pair production in combined laser and Coulomb fields
The optical theorem is applied to the process of electron-positron pair
creation in the superposition of a nuclear Coulomb and a strong laser field. We
derive new representations for the total production rate as two-fold integrals,
both for circular laser polarization and for the general case of elliptic
polarization, which has not been treated before. Our approach allows us to
obtain by analytical means the asymptotic behaviour of the pair creation rate
for various limits of interest. In particular, we consider pair production by
two-photon absorption and show that, close to the energetic threshold of this
process, the rate obeys a power law in the laser frequency with different
exponents for linear and circular laser polarization. With the help of the
upcoming x-ray laser sources our results could be tested experimentally.Comment: 10 pages, 3 figure
Subcycle time-resolved nondipole dynamics in tunneling ionization
The electron nondipole dynamics in tunneling ionization in an elliptically polarized laser field is investigated theoretically using a relativistic Coulomb-corrected strong-field approximation (SFA) based on the eikonal approximation of the Klein-Gordon equation. We calculate attoclock angle-resolved light-front momentum distributions at different ellipticities of the laser field in quasistatic and nonadiabatic regimes and analyze them with an improved Simpleman model. The nondipole correlations between longitudinal and transverse momentum components are examined. Deviations of the photoelectron momentum distribution calculated via SFA with respect to the available experimental results as well as with the improved Simpleman model are discussed and interpreted in terms of nonadiabatic as well as Coulomb effects in the continuum and under-the-barrier. The favorable prospects of an experimental observation are discussed
- …