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The effect of realistic nuclear charge distributions on atomic levels and transitions

Papoulia, Asimina LU (2015) FYSM31 20151
Department of Physics
Mathematical Physics
Abstract
Analogue atomic spectral lines from different isotopes display a small shift in energy, commonly referred as the frequency isotope shift. One of the components of the isotope shift is the field shift, which depends on the extent and the shape of the nuclear charge density distribution. In this work, we investigate how sensitive field shifts are with respect to variations in the nuclear size and shapes. It is found that realistic shapes of nuclei can have a considerable effect in the prediction of the field shifts. Using a novel approach, we demonstrate the possibility to extract new information concerning the nuclear charge densities from the observed field shifts.
Popular Abstract
The abundance of an isotope for a particular element varies between different astronomical objects and on a long-term scale it also varies from time to time depending on its decay rate. Therefore, the knowledge of the origin and evolution process of the astronomical objects existing in the Milky Way and other Galaxies depends not only on their elemental but also on their isotopic composition. Although the chemical composition of the Earth is well known, the study of the isotopes abundance in various stars and other planets is still of great interest. In addition, such studies are not restricted to the natural elements. They can also be expanded into the investigation of radioactive isotope abundances, artificially produced in laboratories.... (More)
The abundance of an isotope for a particular element varies between different astronomical objects and on a long-term scale it also varies from time to time depending on its decay rate. Therefore, the knowledge of the origin and evolution process of the astronomical objects existing in the Milky Way and other Galaxies depends not only on their elemental but also on their isotopic composition. Although the chemical composition of the Earth is well known, the study of the isotopes abundance in various stars and other planets is still of great interest. In addition, such studies are not restricted to the natural elements. They can also be expanded into the investigation of radioactive isotope abundances, artificially produced in laboratories.

Light coming from astronomical objects can be analyzed through the resulting spectra. Most commonly the energy spectra consist of several lines of different wave-lengths and intensities. For a particular element, the spectra of the various isotopes are very similar. A small shift in wave-length is however observed, known as the frequency isotope shift. As a result, the intensity of such peaks represents the isotopes abundance. By measuring the difference in frequency between two peaks representing analogue transitions, we can calculate the corresponding difference between the nuclear radii of the isotopes represented by these peaks. Thus, by using one isotope as reference we can identify the existing variety of isotopes.

For light nuclei, the difference in frequency is dominated by the difference in the second order radial moment, since the contribution of higher order radial moments of the nuclear charge density distribution on the frequency shift is almost negligible. On the other hand, in heavier systems the higher moments contribute to a particular percentage to this shift. Many of the atomic structure packages that are currently available for computing atomic properties approximate the nuclear charge distributions using the Fermi model. However, it seems that the observed isotope shift is rather sensitive to the nuclear properties. This thesis work provides a study of the effect that the higher order radial moments from realistic nuclear charge distributions may have on the frequency isotope shifts, as well as an estimate of whether this effect can be observed or not.

By comparing with the observed isotope shifts in heavy systems, it may be possible to extract the higher order radial moments of the nuclear charge distributions. Therefore, further conclusions can be drawn on the deformation, density wiggles etc. of the distributions in such systems. A novel method is introduced and it can be used e.g. for the extraction of the first two even radial nuclear moments. This thesis is restricted to the study of lithium-like systems, where the measurements of the isotope shifts are currently performed with large uncertainty. However, in neutral systems the measurements are carried out with higher precision and thus, the extraction of the nuclear moments may be achieved with smaller errors. (Less)
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author
Papoulia, Asimina LU
supervisor
organization
course
FYSM31 20151
year
type
H2 - Master's Degree (Two Years)
subject
keywords
nuclear charge density distributions, nuclear radial moments, frequency isotope shift, isotope field shift
language
English
id
7360031
date added to LUP
2015-06-16 23:22:31
date last changed
2016-02-26 15:39:00
@misc{7360031,
  abstract     = {Analogue atomic spectral lines from different isotopes display a small shift in energy, commonly referred as the frequency isotope shift. One of the components of the isotope shift is the field shift, which depends on the extent and the shape of the nuclear charge density distribution. In this work, we investigate how sensitive field shifts are with respect to variations in the nuclear size and shapes. It is found that realistic shapes of nuclei can have a considerable effect in the prediction of the field shifts. Using a novel approach, we demonstrate the possibility to extract new information concerning the nuclear charge densities from the observed field shifts.},
  author       = {Papoulia, Asimina},
  keyword      = {nuclear charge density distributions,nuclear radial moments,frequency isotope shift,isotope field shift},
  language     = {eng},
  note         = {Student Paper},
  title        = {The effect of realistic nuclear charge distributions on atomic levels and transitions},
  year         = {2015},
}