Novel nuclear laser spectroscopy method using superfluid helium for measurement of spins and moments of exotic nuclei

•Development of a novel nuclear laser spectroscopy method using superfluid helium.•Observation of the Zeeman resonance with the 85Rb beam introduced into helium.•Demonstration of deducing the nuclear spins from the observed resonance spectrum. We have been developing a novel nuclear laser spectroscopy method “OROCHI” for determining spins and moments of exotic radioisotopes. In this method, we use superfluid helium as a stopping material of energetic radioisotope beams and then stopped radioisotope atoms are subjected to in situ laser spectroscopy in superfluid helium. To confirm the feasibility of this method for rare radioisotopes, we carried out a test experiment using a 85Rb beam. In this experiment, we have successfully measured the Zeeman resonance signals from the 85Rb atoms stopped in superfluid helium by laser-RF double resonance spectroscopy. This method is efficient for the measurement of spins and moments of more exotic nuclei.