Laser spectroscopy of fermium isotopes and development of an actinide ion mobility spectrometer
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Abstract
Research on heavy and superheavy elements deepens the understanding of the limits of nuclear existence and gives an insight of the underlying structure of atoms. Atoms beyond fermium ($Z$=100) owe their existence to nuclear shell effects.
However, the access to heavy actinides and transactinides is challenging due to low production yields and short half-lifes.
To investigate both the electronic and nuclear structure of an element, laser Resonance Ionization Spectroscopy (RIS) provides a model-independent technique.
This work covers the spectroscopic isotope shift measurement of an atomic transition of the fermium isotopes $^{248,249,250}$Fm. Moreover, isotope shift values obtained from broad band spectroscopy on off-line available $^{255,257}$Fm are included. From the isotope shifts, the mean-square charge radii (mscr) are extracted on both sides of the deformed neutron shell gap $N$=152. The experimental data are compared with different nuclear models.
To investigate the electronic structure of actinides, ion mobility spectrometry (IMS) can provide an alternative approach. Previous IMS measurements on lanthanide ions revealed the dependence of ion-atom interactions on the underlying electronic configuration. For an extension of IMS to the actinides, an actinide ion mobility spectrometer has been developed. An implemented cryogenic drift cell allows systematic mobility measurements at varying temperatures and pressures.