EGAS41 - Swansea University

41 st EGAS CP 106 Gdańsk 2009
Changes of the electron charge density of E1, M1, E2 and
mixed type transitions of lead
T.J. Wasowicz 1,2,∗
1 Institute of Experimental Physics, University of Gdansk, ul. Wita Stwosza 57,
80-952 Gdansk, Poland
2 Department of Physics of Electronic Phenomena, Gdansk University of Technology,
ul. Gabriela Narutowicza 11/12, 80-233 Gdansk, Poland
∗ E-mail: fiztw@univ.gda.pl
The isotope shift of atomic spectral lines consists of two contributions, this caused by
the finite nuclear mass and that resulting from the field effect. In heavy elements (such
as lead) the mass effect is negligible and the field effect, which increases with increasing
Z, roughly accounts for the observed shifts. The field shift originates from the changes
of the size and shape of the nuclear charge distribution when neutrons are added to the
nucleus. As a consequence the binding energies of electrons which penetrate the nucleus
differ among various isotopes. Thus the field shift is the result of multiplying a nuclear
parameter and an electronic factor (F i ). The F i depends on the changes of the electron
charge density at the nucleus ∆ |ψ(0)| 2 i
in the i transition as follows:
F i = πa 3 0∆ |ψ(0)| 2 i
f(Z)/Z (1)
There are three ways by which this quantity can be obtained. It can be taken from
experiments, but also it can be calculated theoretically by the use of both ab initio or
semiempirical methods. Theoretical data available in literature for the ∆ |ψ(0)| 2 i
of the
allowed and multipole lines of lead are scant. Calculations of the probability densities for
the lowest configurations of PbI have only been performed in [1,2]. To our knowledge
there are no experimental data concerning this problem. So, the analysis of the 24 allowed
(E1) [3] and forbidden (M1, E2 and M1+E2) [4] transitions of lead have been performed
and the changes of the electron charge densities have been determined.
The measurement of the ∆ |ψ(0)| 2 i
can provide a test of theoretical wave-function
calculations. These values can be also compared with the calculated screening ratios. In
addition accurate knowledge of field shifts and the probability densities can be essential
for future measurements of parity nonconserving optical rotation in lead.
References
[1] W.H. King, M. Wilson, J. Phys. G: Nucl. Phys. 11, L43 (1985)
[2] S. Bouazza, D.S. Gough, P. Hannaford, R.M. Lowe, M. Wilson, Phys. Rev. A 63,
0125161 (2001)
[3] T.J. Wasowicz, Eur. Phys. J. D (2009) DOI: 10.1140/epjd/e2009-00133-6
[4] T.J. Wasowicz, S. Werbowy, R. Drozdowski, J. Kwela, Europhysics Conference Abstracts
32E, 202, Graz (2008)
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