ABSORPTION-SPECTRUM OF THE P O-18 MOLECULE - SIGMA-2 AND DELTA-2-X2II TRANSITIONS - PERTURBATION EFFECTS ON THE INTENSITY OF LINES IN THE E DELTA-2-X2II TRANSITION

The **2 SIGMA and **2 DELTA -X**2II absorption transitions of the P**1**8O molecule are surveyed in the region 1800-2500 A, giving some new details on the C**2 SIGMA ** minus , F**2 SIGMA ** plus , and G**2 SIGMA ** plus states. The electronic homogeneous interactions between the E**2 DELTA Rydberg state and the C prime **2 DELTA valence state are pointed out and it is shown that the perturbations rather than predissociations are responsible for the main intensity anomalies and gaps previously observed in the structure of the E**2 DELTA -X**2II emission bands.