the early type stars, the dominant spectral features are HeI 5882 cm$^{-1}$ (1.700 $\mu$m) and the Brackett series of hydrogen from lines 4-10 (1.736 $\mu$m) to 4-16 (1.556 $\mu$m). The He I line exceeds the strength of the Brackett lines in the very earliest stars (06 to B0), with a maximum equivalent width of $\sim 0.83$ cm$^{-1}$ (HR1903; B0 Ia), and recedes to undetectable levels ($\sim 0.10$ cm$^{-1}$) by spectral type B8. From the late B to early F stars, the Brackett series dominates the spectrum, after which lines of neutral atomic metals begin to take prominence. The strongest metallic lines include MgI, SiI, CaI, AlI, and FeI, which increase in strength toward the K stars. Finally molecular features of OH and CO dominate the spectra of the latest–type stars from K5–M5. The most striking luminosity-sensitive feature is the second–overtone CO bandhead $[v, v^{'} = 6, 3]$ at 6177 cm$^{-1}$ (1.619 $\mu$m), which is found in the spectra of the K and M stars. This feature is signficantly stronger in stars of lower surface gravity at equivalent spectral type.

To further enable spectral classification in the H–band, we have identified a set of 9 features which are prominent in stars 