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We present high resolution near-infrared spectroscopy of two young bipolar planetary nebulae M2-9 and M1-92. These longslit observations were made with the Cryogenic Grating Spectrometer on the 2.1m telescope at KPNO. We detect H$_2$ emission from both nebulae. We determine that this emission is radiatively excited in M2-9. Phillips et al. (1985) detected the 2.122$\mu$m line of H$_2$ in M2-9 using a 12 arcsec beam and speculated that this emission was confined to the central regions of the object. Using our longslit data, we conclude that the H$_2$ emission is actually not present in the core of the object, but rather is confined to the lobes of M2-9. We compare the spatial distribution of the H$_2$ to that of Br$\gamma$ and optical lines.
We find that the H$_2$ emission in M1-92 is thermally excited. Previous work by Trammell et al. (1993) showed that the optical spectrum of M1-92 is dominated by shock emission produced in the lobes of the object. By comparing the optical line ratios to published shock models, we determined the velocity of this shock to be 80-100 kms$^{- 1}$. We now compare our measured H$_2$ line ratios with published shock models to estimate the shock velocity implied by the IR lines. By comparing the IR velocities to the velocities indicated by the optical lines, we unify studies of the shocked material at different wavelengths.
\vskip 0.2in \noindent This work was supported in part by NSF grant 91-15101.
