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Momentum Distribution (momentum + distribution)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Cover Picture: Laser Phys.

LASER PHYSICS LETTERS, Issue 6 2010
Lett.
In the calculations, we also have a very special angular distribution for the slow electrons observed in the case of Ti:Sapphire laser pulse. The appearance of slow electrons is clearly demonstrated at the angularlyresolved 2D momentum distribution which low-energy part is presented in this figure. The observed 2D low-momentum distribution seems to be very consistent with the total momentum distribution: the angular directions of preferable electron ejection can be evidently seen. At other directions, the electron ejection is suppressed. The appearance of such directions of predominant or suppressed electron ejection results from the interference of the different waves in electron wave packet during its recollision with the parent ion. (Cover picture: I.A. Burenkov, A.M. Popov, et al., pp. 409,434, in this issue) (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Vacancy-type defects and electronic structure of perovskite-oxide SrTiO3 from positron annihilation

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2006
A. S. Hamid
Abstract The vacancy-type defects in Nb-doped SrTiO3 and in undoped SrTiO3, annealed in H2 flow, were investigated by means of positron lifetime and 2D angular correlation of annihilation radiation (ACAR) experiments. The calculations of the lifetime of positron were performed by using atomic superposition (AT-SUP) method. The results showed that positrons annihilate from a free state in the Nb-doped SrTiO3. The trapping centers in the annealed sample were found to be oxygen vacancies VO associated with relaxation of the surrounding ions. Moreover, the momentum distributions of the samples studied were correlated to the variation of their electronic structure. It was proposed from the drastic change in the momentum distribution upon introduction of VO, that 2D-ACAR technique is a sensitive tool for acquiring information on the electronic and bond structure of the perovskite-oxides. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The high-density electron gas: How momentum distribution n (k) and static structure factor S(q) are mutually related through the off-shell self-energy , (k, ,)

ANNALEN DER PHYSIK, Issue 10 2010
P. Ziesche
For the spin-unpolarized uniform electron gas, rigorous theorems are used (Migdal, Galitskii-Migdal, Hellmann-Feynman) which allow the calculation of the pair density, g(r), or equivalently its Fourier transform, the static structure factor, S(q), from the dynamical 1-body self-energy , (k, ,), supposing the self-energy is (approximately) known as a functional, depending on the kinetic energy of a single electron, t(k), and on the bare Coulomb repulsion between two electrons, v(q). With the momentum distribution, n(k), and with the kinetic (t) and potential (v) components of the total energy e = t + v, the respective steps are: (i) , (k, ,) , n(k) , t, (ii) , (k, ,) , v, (iii) t + v = e, S(q). How this general scheme works in detail is shown explicitly for the high-density limit (as an illustration). For this case the ring-diagram partial summation or random-phase approximation applies. In this way, the results of Macke (1950), Gell-Mann/Brueckner (1957), Daniel/Vosko (1960), Kulik (1961), and Kimball (1976) are summarized in a coherent manner. Besides, several identities were brought to the light, e.g. the Kimball function for S(q) proves to be identical with Macke's momentum transfer function I(q) for e. [source]

Vacancy-type defects and electronic structure of perovskite-oxide SrTiO3 from positron annihilation

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2006
A. S. Hamid
Abstract The vacancy-type defects in Nb-doped SrTiO3 and in undoped SrTiO3, annealed in H2 flow, were investigated by means of positron lifetime and 2D angular correlation of annihilation radiation (ACAR) experiments. The calculations of the lifetime of positron were performed by using atomic superposition (AT-SUP) method. The results showed that positrons annihilate from a free state in the Nb-doped SrTiO3. The trapping centers in the annealed sample were found to be oxygen vacancies VO associated with relaxation of the surrounding ions. Moreover, the momentum distributions of the samples studied were correlated to the variation of their electronic structure. It was proposed from the drastic change in the momentum distribution upon introduction of VO, that 2D-ACAR technique is a sensitive tool for acquiring information on the electronic and bond structure of the perovskite-oxides. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]