On laser spectroscopy of the element nobelium (Z = 102)

Optical transitions were sought for in 254No, which was produced at the UNILAC accelerator at GSI in the reaction 208Pb (48Ca, 2n)254No. After separation from the projectile beam by the velocity filter SHIP, the nobelium ions were stopped inside a buffer gas cell and guided onto a tantalum filament. The activation energy for desorption of nobelium from tantalum was determined to be 246 (24) kJ/mol. In a first experiment, the search for the 7s7p 1P1 level of nobelium by laser resonance ionization spectroscopy was started. Based on level predictions by multi-configuration Dirac-Fock and relativistic coupled-cluster calculations, the wavenumber ranges from 25 900 cm-1 to 28 260 cm-1 and from 28 040 cm-1 to 31 000 cm-1 were scanned with two excimer laser-pumped dye lasers and a frequency doubled Nd:YAG laser pumped OPO system, respectively. The measurements delivered no clear evidence for a resonance. However, five wavenumber positions, viz. 27 997 cm-1, 28 015 cm-1, 28 230 cm-1, 28 792 cm-1, and 29 516 cm-1, remain potential candidates for the transition and subject for upcoming investigations.