Transition probabilities in the neutral argon spectrum

Measurements are reported for the transition probabilities of the 7635, 6416, 6032 and 4259 Å spectrum lines of neutral argon relative to the most probable value of 6·77 × 10 −6 s −1 recommended by Weise. No systematic trend in the measured values was observed in the pressure range 760 to 76 Torr, or for electron densities ranging from 8 × 10 15 to 2·5 × 10 15 electron/cm 3 . The question of collisional-radiative equilibrium is discussed in the light of measurements made at pressures down to 2 Torr, and it is shown that significant departures from LTE are to be expected only for pressures below 76 Torr.