2,923 research outputs found
Pure spin-angular momentum coefficients for non-scalar one-particle operators in jj-coupling
A revised program for generating the spin-angular coefficients in
relativistic atomic structure calculations is presented. When compared with our
previous version [G.Gaigalas, S.Fritzsche and I.P.Grant, CPC 139 (2001) 263],
the new version of the Anco program now provides these coefficients for both,
scalar as well as non-scalar one-particle operators as they arise frequently in
the study of transition probabilities, photoionization and electron capture
processes, the alignment transfer through excited atomic states, collision
strengths, and in many other investigations.
The program is based on a recently developed formalism [G.Gaigalas,
Z.Rudzikas, and C.F.Fischer, J. Phys. B 30 (1997) 3747], which combines
techniques from second quantization in coupled tensorial form, the theory of
quasispin, and the use of reduced coefficients of fractional parentage, in
order to derive the spin-angular coefficients for complex atomic shell
structures more efficiently. By making this approach now available also for
non-scalar interactions, therefore, studies on a whole field of new properties
and processes are likely to become possible even for atoms and ions with a
complex structure
Maple procedures for the coupling of angular momenta. VI. LS-jj transformations
Transformation matrices between different coupling schemes are required, if a
reliable classification of the level structure is to be obtained for open-shell
atoms and ions. While, for instance, relativistic computations are
traditionally carried out in jj-coupling, a LSJ coupling notation often occurs
much more appropriate for classifying the valence-shell structure of atoms.
Apart from the (known) transformation of single open shells, however, further
demand on proper transformation coefficients has recently arose from the study
of open d- and f-shell elements, the analysis of multiple--excited levels, or
the investigation on inner-shell phenomena. Therefore, in order to facilitate a
simple access to LS jj transformation matrices, here we present an
extension to the Racah program for the set-up and the transformation of
symmetry-adapted functions. A flexible notation is introduced for defining and
for manipulating open-shell configurations at different level of complexity
which can be extended also to other coupling schemes and, hence, may help
determine an optimum classification of atomic levels and processes in the
future
Compton scattering of twisted light: angular distribution and polarization of scattered photons
Compton scattering of twisted photons is investigated within a
non-relativistic framework using first-order perturbation theory. We formulate
the problem in the density matrix theory, which enables one to gain new
insights into scattering processes of twisted particles by exploiting the
symmetries of the system. In particular, we analyze how the angular
distribution and polarization of the scattered photons are affected by the
parameters of the initial beam such as the opening angle and the projection of
orbital angular momentum. We present analytical and numerical results for the
angular distribution and the polarization of Compton scattered photons for
initially twisted light and compare them with the standard case of plane-wave
light
Correlated EoM and Distributions for A=6 Nuclei
Energy spectra and electromagnetic transitions of nuclei are strongly
depending from the correlations of the bound nucleons. Two particle
correlations are responsible for the scattering of model particles either to
low momentum- or to high momentum-states. The low momentum states form the
model space while the high momentum states are used to calculate the G-matrix.
The three and higher order particle correlations do not play a role in the
latter calculation especially if the correlations induced by the scattering
operator are of sufficient short range. They modify however, via the long tail
of the nuclear potential, the Slater determinant of the A particles by
generating excited Slater's determinants. In this work the influence of the
correlations on the level structure and ground state distributions of even open
shell nuclei is analyzed via the boson dynamic correlation model BDCM. The
model is based on the unitary operator ({\it S} is the correlation
operator) formalism which in this paper is presented within a non perturbative
approximation. The low lying spectrum calculated for Li reproduce very well
the experimental spectrum while for He a charge radius slightly larger than
that obtained within the isotopic-shift (IS) theory has been calculated. Good
agreement between theoretical and experimental results has been obtained
without the introduction of a genuine three body force.Comment: 25 pages 4 figures. To be published in the Progress Theoretical
Physic
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