Molecular Hydrogen Emission from the Photodissociation Region in Hubble 12

Infrared spectra of molecular hydrogen (H2) line emission, from the photodissociation region in the planetary nebula Hubble 12, are presented. The spectra range between 0.7 and 2.5 um. Approximately 75 H2 lines were measured with over 100 lines actually detected. The ortho/para ratio for H2 was measured and it is shown that there is a decreasing trend in this ratio with energy level. This is qualitatively interpreted as the radiative excitation of 'fresh' molecules from the molecular cloud by a still evolving and young photodissociation region.