Abstract. Neutron rich 2~(T1/2 =5.2 min) was produced and on-line mass separated at the ISOLDE facility at CERN. The polarization achieved by optical pumping via the atomic line (6s 2 ~S 0,--,6s 6p 3P t, 2 = 2 537 A) was monitored by the/~ decay asymmetry. Hyperfine structure and isotopic shift of the 2~ absorption line was determined by Zeeman scanning. In addition a magnetic resonance was performed on the polarized