Abstract
An approximate formula for the computation of the free-bound emission coefficient for hydrogenic ions is presented. The approximation is obtained through a manipulation of the (free-bound) Gaunt factor which intentionally distinguish the dependence on frequency from the dependence on temperature and ionic composition. Numerical tests indicate that the derived formula is very precise, fast and easy to use, making the calculation of the contribution from an ionized region of varying temperature and ionic composition a very simple and time saving task.
