NEUTRAL ATOMIC CARBON IN THE GLOBULES OF THE HELIX

We report detection of the 609 mu m P-3(1) --> P-3(0) line of neutral atomic carbon in globules of the Helix Nebula. The measurements were m ade toward the position of peak CO emission. At the same position, we obtained high-quality CO(2-1) and (CO)-C-13(2-1) spectra and a 135 '' x 135 '' map in CO(2-1). The velocity distribution of CI shows six nar row (1-2 km s(-1)) components, which are associated with individual gl obules traced in CO. The CI column densities are (0.5-1.2) x 10(16) cm (-2). CI is found to be a factor of similar to 6 more abundant than CO . The large abundance of CI in the Helix can be understood as a result of the gradual photoionization of the molecular envelope by the centr al star's radiation field.