Spectra of the Monoxides of Cerium and Praseodymium

Vibrational quantum assignments are presented for five sparsely developed emission band systems of CeO and one of PrO. Comparison is made with two known GdO systems (Piccardi) and one LuO system (Watson and Meggers). Nd has no evident oxide spectrum in the flame of the arc, and Meggers and Scribner report none for Yb and Tm. Reasons for the general poor development or complete lack of oxide band systems for a number of the rare earths are discussed. Fairly intense band systems seem to exist only for those rare earths having a $d$ electron in their normal configuration.