Electron-impact broadening of radio recombination lines of atomic hydrogen for different Δn

In 1967 Griem gave a general formula for the electron-impact broadening of radio recombination lines, and an approximate expression for the width of the Delta n = 1 lines. Here his general formula is calculated numerically for higher values of Delta n, and an approximate expression is fitted to the results for Delta n up to 70. It is shown that, for the lines with different n and Delta n near a given frequency v, the calculated widths increase monotonically up to n > 300. This result does not agree with the maximum found near n approximate to 200 by Bell et al (2000 Publ. Asti-on. Soc. Pac. 112 1236) for the astronomical sources W51 and Orion A at 6 GHz. Thus this mystery is not resolved by the present calculations.