Relative intensities of 3p-3s transitions in neonlike Ar IX

Argon was added in small amounts to θ-pinch discharges in hydrogen and deuterium, and the relative intensities of all 3p→3s transitions of neonlike argon were measured at the peak of the Ar IX concentration. At this time recombination was small since the ion was in an ionizing regime; effective excitation of the 3p levels was essentially due to direct collisional excitation from the ground state and cascading contributions after excitation to higher levels. The relative intensities are compared with theoretical calculations, which employed various collisional and radiative transition rates given in the literature. Very good overall agreement is obtained with a collisional-radiative model which includes all levels up to n=5