In-gas-cell laser ionization spectroscopy of Os 194 , 196 isotopes by using a multireflection time-of-flight mass spectrograph

We performed in-gas-cell laser ionization spectroscopy of Os-194,Os-196, which were produced by multinucleon transfer reactions at the KEK Isotope Separation System (KISS). The nuclei of interest were identified through beta-decay spectroscopy and a newly applied multireflection time-of-flight mass spectrograph (MRTOF-MS). From the study of laser resonance spectra, isotope shifts (ISs) of the transition lambda(1) = 247.758 nm for Os-194 and Os-196 were measured for the first time. The change in the mean-square charge radius delta < r(2)>(192,A) and the quadrupole deformation parameter (1/2) were deduced from the IS measurements. The results were compared with the theoretical calculations and the predicted shape transition at Os-194 is discussed.