For theB²Σ andX²Σ states of scandium monoxide, the potential energy curves are constructed by the Rydberg-Klein-Rees and the Morse methods. Morse model is shown to be adequate for the (B→X) band system of ScO. The r_e values are found to be 1.717 Å and 1.665 Å for theB andX states respectively.

Franck-Condon factors andr-centroids based on Rydberg-Klein-Rees potential have been computed for the CP (B²Σ⁺ —A²Π_i) band system. These results are compared with the Morse values and discussed.

The integrated intensities of a few bands in the vibrational structure of the astrophysically significant ‘orange’ system of the molecule yttrium monoxide, have been measured experimentally by the technique of photographic photometry. The effective vibrational temperatures of the source are found to be 2402±180 K and 2901±230 K for the subsystemsA²Π_3/2−X²Σ⁺ andA²Π_1/2−X²Σ⁺ respectively.