On the Narrowing of Radio Recombination Lines at High Principal Quantum Numbers

Abstract

Limitations of a recent attempt by Oks to explain the decrease of line widths for principal quantum numbers beyond n ≈ 200, as observed by Bell et al. in H II regions, are discussed. Improved estimates of the ion Weisskopf radius and strong-collision impact parameter support previous calculations of the Stark widths, thus invalidating the proposed explanation of the observed decreases of line widths at large n.