  We investigate the loss rates of the hydrogen atmospheres of terrestrial
planets with a range of masses and orbital distances by assuming a stellar
extreme ultraviolet (EUV) luminosity that is 100 times stronger than that of
the current Sun. We apply a 1D upper atmosphere radiation absorption and
hydrodynamic escape model that takes into account ionization, dissociation and
recombination to calculate hydrogen mass loss rates. We study the effects of
the ionization, dissociation and recombination on the thermal mass loss rates
of hydrogen-dominated super-Earths and compare the results to those obtained by
the energy-limited escape formula which is widely used for mass loss evolution
studies. Our results indicate that the energy-limited formula can to a great
extent over- or underestimate the hydrogen mass loss rates by amounts that
depend on the stellar EUV flux and planetary parameters such as mass, size,
effective temperature, and EUV absorption radius.
