Pressure-induced H2 opacity in the 5-μm region

The H₂ opacity arising from the pure-rotational hexadecapole-induced U₀(J) transitions occurring during H₂H₂ and H₂He collisions, and from the hexadecapole-induced U₀(J) + S₀(J′) and the quadrupole-induced S₀(J) + S₀(J′) transitions in H₂He collisions, has been calculated. The U₀(J) and S₀(J) + S₀(J′) contributions from H₂H₂ collisions are important H₂ opacities in the frequency range from 700–3000 cm^?1 for temperatures appropriate to the outer planets. It is concluded that this opacity is needed in addition to the opacity from the extrapolation of the 0-0 and 1-0 H₂H₂ collisionally induced bands to interpret the spectrum at 5 μm for the outer planets.