Comparison of experimental results and different theoretical approaches to collisional effects on spectral lines of molecular ions

Different methods of calculations are compared to experimental results for the collisional lineshape effects on the rotational transitions of molecular ions surrounded by a neutral buffer gas. Capture method and Anderson Tsao Curnutte (ATC) method with straight line trajectories are both not able to reproduce the measurements. A discussion of the origin of such a discrepancy allows to obtain better insights into the different mechanism of collisional relaxation. Quite good agreement is obtained both by the hybrid method proposed by Liao and Herbst or by ATC calculations using a more realistic translational dynamics.