Measurement of the photoionization cross section from the laser-populated³D metastable levels in barium

The authors have measured the absolute photoionization cross section from the 6s5d 3 D metastable level of barium. The 3 D levels were selectively populated with a high-power, tuneable dye laser. The cross section obtained at 303 nm was (18+or-4)*10 -18 cm 2 . The number density was determined by observing the resulting depopulation of the ground state when pumping occurred.