Calculations are carried out on the absorption of an atmosphere of H, |$\text{H}^{+}\,\text{and}\,\text{H}_{2}^{+}$| using the accurate quantal dipole moment but treating the nuclei as classical particles. Absorption coefficients are tabulated for wave numbers between 500 cm–1 and 26 000 cm–1, and for temperatures between 2 500 deg. K and 12 000 deg. K. The relative importance of bound-free and free-free transitions is also determined.