Lifetime measurements of the La II y³F₄,₃,₂⁰levels with the beam-laser method (solar photosphere La abundance)

Fast La + ions are excited selectively from the a 3 F levels to the y 3 F 0 levels by the radiation inside the cavity of a tunable dye laser. The intensity distributions of the cascade-free decays downstream yield the following lifetimes: y 3 F 4 0 : 455+or-11 ns, y 3 F 3 0 : 430+or-10 ns and y 3 F 2 0 : 511+or-13 ns. These lifetimes are in order of magnitude shorter than those inferred from the emission data of Corliss and Bozman (1962). The significance of the new lifetime values for the determination of the La abundance in the solar photosphere is discussed.