Use of the Van Regemorter formula for collision strengths or cross sections

The accuracy of the widely used Van Regemorter formula [Astrophys. J. 136, 906 (1962)] for calculating the collision strengths needed in applications to high-temperature plasmas is tested by comparison with numerous more accurate calculations. It is found to be frequently a very poor approximation, especially for {Δ}n{≥}1 excitation transitions from levels with ln-1, and the recommendation is made that with the recent advances in calculational procedures and available accurate atomic data use of the Van Regemorter formula should be discontinued.