ISOTOPE-SELECTIVE PHOTOIONIZATION SPECTROSCOPY OF BARIUM

We demonstrate an experimental technique that selects the nuclear spin I = 0 isotope Ba-138 for spectroscopic measurements from a beam of natural barium containing seven stable isotopes. A cw dye laser is used to optically pump the I = 3/2 isotopes Ba-135 and Ba-137 into the metastable 6s5d 1D2 and 3D1,2 levels via the 6s6p P-1(1) excited state, leaving nearly pure Ba-138 in the ground state. Photoionization spectra Of the excited 5d6p 3D1 even isotope state recorded with optical pumping of Ba-135 and Ba-137 to the Metastable levels are essentially devoid of forbidden features associated with the hyperfine interaction in the odd isotopes.