Experimental transition probabilities and Stark shifts in O III and O IV spectra

On the basis of the relative line intensity ratio (RLIR) method transition probability values of the spontaneous emission (Einsteinʹs A values) of 41 astrophysically important transitions (in 15 multiplets) in the doubly (O III) and 7 transitions (in 5 multiplets) in triply (O IV) ionized oxygen spectra have been obtained relative to the reference A values related to the 326.085 nm O III and 340.355 nm O IV, most intensive transitions in the O III and O IV spectra. Fourteen of the investigated O III lines belong to the cascades in the astrophysically important Bowen fluorescence mechanism. Most of the O III transition probability values are the first data obtained experimentally using the RLIR method. Stark shift values (d) of the mentioned lines are also measured. Twenty three of them were not known and represent the first data in this field. Our A and d values are compared to available experimental and theoretical data. A linear, low-pressure, pulsed arc was used as an optically thin plasma source operated in oxygen discharge at a 42 000 K electron temperature and 1.65*10^23 m^ -3 electron density.