We present coefficients for the calculation of the continuous emission spectra of H i , He i and He ii due to electron-ion recombination .
Coefficients are given for photon energies from the first ionization threshold for each ion to the n = 20 threshold of hydrogen ( 36.5 \mu ) , and for temperatures 100 K ~ { } \leq~ { } T~ { } \leq~ { } 10 ^ { 5 } K. The emission coefficients for He i are derived from accurate ab initio photoionization data .
The coefficients are scaled in such a way that they may be interpolated by a simple scheme with uncertainties less than 1 % in the whole temperature and wavelength domain .
The data are suitable for incorporation into photoionisation/plasma codes and should aid with the interpretation of spectra from the very cold ionised gas phase inferred to exist in a number of gaseous clouds .