0 Report NPI Řež – TH – 01 / 2000 Tables of internal conversion coefficients for superheavy elements

A. Introduction. — At present, the attempt to synthetize superheavy elements is one of important tasks of modern physics. The study of the structure of such isotopes is then a question of a near future. Very recently, in the isotope of 254 No (Z=102), the ground-state band of even–even nucleus up to spin 14 was identified [1]. Moreover a production of more heavier element – Z=118, A=293 – was indicated [2]. Then a further development of γ–ray spectroscopy can be expected. However, for such high Z's, the internal conversion strongly prevails over the emission of γ–rays and must be taken into account. In this work we present the internal conversion coefficients (ICC) for superheavy elements 104≤Z≤126. B. Calculations. — The ICC were calculated using the computer program NICC [3]. The program solves the Dirac equation for both bound and free electron states using the formulae by Büring [4]. Then it performs direct integration with reasonably small step to obtain the conversion matrix elements. The atom is described by a Hartree–Fock–Slater potential, the nucleus is expected to bear the Fermi charge distribution. In this work, we use the potential of Lu et al [5]. Usually, the kinetic energy of the converted electron is derived from experimental binding energy of that electron prior to conversion. Due to the absence of the experimental data, we use the eigenvalues from [5] instead. Those eigenvalues are known to be close to the experimental binding energies where available (within tens of eV for inermost shells, within eV's for the outermost shells). Moreover, the dependence of the theoretical ICC on the kinetic energy of the emitted electron (except if this energy is close to zero, i.e. for transition energies near to the threshold for the particular subshell) is not too strong. For Z=104 only, we can compare our ICC with those of Rösel et al [6] and Band and Trzhaskovskaya [7]. For comparison, we have chosen the former ones since they are calculated using almost the same atomic model as we used. In most cases, the agreement is better than 1 percent, only exceptionally within 2 – 3 percent.