“…During the last years, we have reported Fourier-transform emission measurements of fine structure transitions in the X 3 R À or X 2 P ground states of a large number of Bi, Te, and Pb containing molecules (BiX, TeX (X = H, F, Cl, Br, I) [8], BiY (Y = O, S, Se) [9], Pb 2 [10], PbX (X = F, Cl, Br, I) [11,12]). In fact, PbH was the only species of these groups for which the fine structure transition had not been observed in spite of some experimental efforts.…”