A summary of the current status of experimentally derived values of the per
manent electric dipole moment, mu, for the 3s, 4s, 5s, and 6s series of tra
nsient metal containing molecules is given. The experimental methods employ
ed are described with particular emphasis placed upon optical Stark measure
ments of supersonic molecular beam samples. The complications associated wi
th the analysis of optical Stark spectra of open shell polyatomic metal con
taining radicals are addressed. An assessment of the applicability of simpl
e molecular orbital correlation diagrams to predict trends in measured Valu
es of mu for early transition metal diatomic molecules is made.