Electron collisional rate coefficients for low-level transitions in hydrogen

In a recent paper, Aggarwal (1983, Mon. Not. R. Astr. Soc. 202,15P) has presented new calculations of the excitation rate coefficients due to electron impact of the n=1 to n'=2 and n=1 to n'=3 transitions in atomic hydrogen, and compared them with the semi-empirical rates of Johnson (1922, Astrophys. J., 174,227s): he has found that the latter calculation can be as much as a factor of 9 too large compared to his new results at temperatures of 5 x 103 K. In fact, Aggarwal has miscalculated the Johnson rates, and their actual values are much closer to his new values than he concluded. Thus, it is not possible to make any general statement that the Johnson rates always tend to be overestimates of the correct rates, particularly at low temperatures. (author)