Tables of Radio-Frequency Recombination Lines

The rest frequencies of radio-frequency recombination lines of hydrogen and helium have been computed and tabulated. The tabulation covers the complete range of frequencies normally used for radio astronomical observations. Transitions with An = 1 through An = 5 are included for hydrogen and An = 1 and An = 2 for helium. Table 1 provides the rest frequencies when the transition is specified. Table 2 provides the rest frequencies in sequence and identifies the transitions. The combined tables offer a convenient reference for planning observations and identifying spectra. Formulae are given from which rest frequencies of heavier elements with arbitrary ionization can be computed with the aid of the tables. Problems associated with line identification are discussed.