  The triatomic hydrogen ion (H$_3^+$) has spurred tremendous interest in
astrophysics in recent decades, and Rydberg states of H$_3$ have also
maintained an important role for understanding H$_3^+$ experiments. In a
previous study [J. Chem. Phys. \textbf{133}, 234302 (2010)], radiative
transitions between neutral H$_3$ Rydberg states were calculated at wavelengths
near 7 microns, and could be compared with mid-infrared laser lines observed in
hydrogen/rare gas discharges. The present study extends the investigation to
wavelengths near 10 -- 13 microns. Rydberg states of D$_3$ are also treated.
