The absorption of infrared and visible radiation from stellar emission spectra by the negatively charged hydrogen ions H ^ { - } is considered .
We derive the explicit formulas which can be used to determine the total absorption coefficient ( per unit volume ) for the negatively charged hydrogen ions ^ { 1 } H ^ { - } ( protium ) and ^ { 2 } H ^ { - } ( deuterium or D ^ { - } ) .
The bound-free and free-free absorption coefficients a _ { \nu } and k _ { \nu } obtained in our methods can be used to evaluate the actual absorption of infrared and visible radiation by the H ^ { - } ion in photospheres of many cold stars with surface temperatures T _ { s } \leq 8,250 K .