Dependences of the populations of the Ar II levels in a CW argon laser on the discharge-tube diameter and magnetic field

The populations of the Ar II laser levels were determined as a function of the current density and the pressure in tubes of 2.8 and 4.8 mm diameter. The higher specific output power obtained from the larger diameter tubes was due to the stronger population inversion. The influence of a longitudinal magnetic field on the populations of the Ar II levels was investigated. The dependence of the inversion on the magnetic field was found to be nonmonotonic: There was an optimal magnetic field in which the inversion was strongest. This behavior of the inversion was attributed to the capture of resonance radiation and depopulation of the upper levels as a result of collisions with electrons. The experimentally determined populations of the Ar II levels were compared with the theoretical values.