Intercombination lines in Zn-like, Ga-like and Ge-like Nb

Abstract

Using beam-foil spectroscopy and comparing prompt spectra (recorded close to the foil) with delayed ones we have observed the n = 4, Δn = 0 spin-forbidden transitions 4s2 1S0-4s4p 3P1o in Zn-like Nb XII, 4s24p 2Po- 4s4p2 4P in Ga-like Nb XI and 4s24p2 3P-4s4p3 5So in Ge-like Nb X. Lifetime measurements support the spectroscopic assignments. The experimental transition probabilities for the 4s2 1S0-4s4p 3P10 intersystem line in the Zn I sequence are compared with the rather differenct results of various theoretical calculations.