Isotope shift studies of the B3 Σ −−X3 Σ − bands of SO

The B³ Σ ^??X³ Σ ^? bands of SO were excited in an electrodeless microwave (2450 Mc/s) discharge through trace amounts of sulphur enriched with 37% of³⁴S and oxygen enriched with about 40% of¹⁸O. The emission spectra of³²S¹⁶O,³⁴S¹⁶O and³²S¹⁸O were photographed on a Jarrell-Ash 3·4 m. grating spectrograph at a dispersion of 5 Å/mm. Isotope shift data obtained from the present studies support the revision of the earlier vibrational scheme (Henri and Wolff, 1929; Martin, 1932) by increasingv″-quantum numbering by two units as suggested by Norrish and Oldershaw (1959).