Polarization in the perturbed spontaneous emission spectrum of an argon II laser

Changes in the intensity of the lines of the spontaneous emission spectrum of a d.c. argon II laser tuned to 4880 Å are produced by chopping the laser radiation field in the cavity. Polarization ratios have been measured for several transitions in this perturbation spectrum. For the two transitions (4880 Å, 4228 Å) from the upper laser level (4p 2 D 5/2 ) the polarization ratio (0.21) is independent of the discharge parameters and the laser intensity. Other transitions with levels collisionally coupled to the upper laser level are found to be unpolarized. A theoretical treatment is given which enables certain parameters (saturation effects, collisional lifetime of the upper laser level) to be evaluated. Magnetic depolarization effects are considered, but a satisfactory theoretical treatment has not been achieved.