Pressure Dependence of Rotationally Perturbed Lines in the Ultraviolet Band Spectrum of Cn

Intensity measurements of the components of rotationally perturbed lines (K' = 4, 7, 11, and 15) in the 0,0 transition of the violet system (B 2 Σ + − X 2 Σ + ) of the CN formed in an "active" nitrogen flame have been made at pressures from 0.1 to 100 mm Hg. A simple kinetic model considering competition between formation, radiation, and collisional interchange of states gives a reasonable fit to the data over the entire range of measured pressures. At high pressures the intensity ratios of the components of rotationally perturbed lines depend only upon the radiative transition probabilities and at low pressures, only upon the relative rates at which they are populated. At intermediate pressures, the intensity ratios depend upon the collision frequency for the interchange of the rotationally perturbed states. The collision frequency determined in this manner is of the same order of magnitude as the gas kinetic collision frequency.