Isotope shift studies of the ultra-violet and visible bands of P<SUP>16</SUP>O and P<SUP>18</SUP>O

The spectra of P16O and P18O were excited in sealed discharge tubes containing neon (2-3 mm. pressure), oxygen gas enriched to 65 per cent. of 18O and trace amounts of phosphorus vapour and photographed on a 3 m. grating spectrograph at a dispersion of 2.5 &#197;/mm. Isotope shift studies in the &#946;-bands confirmed the earlier vibrational scheme of Curryet al. and showed conclusively that the red as well as the violet degraded bands belonged to the same &#946;-system. The present studies of isotope shifts also confirmed the vibrational assignments of the extensive ultraviolet bands involving the 2&#8721;--X2&#928; transition and the &#947;-bands (A2&#8721;+-X2&#928;). In the case of the visible bands, they provided evidence for the first time that the bands at 5585&#197;, 5962&#197; and 6385&#197; belonged to one system and involved 0-0, 0–1 and 0–2 transitions respectively