Far-infrared spectroscopy of C II and high-J CO emission from warm molecular gas in NGC 3576

We have observed the 158 mu m P-2(3/2) <-- P-2(1/2) fine-structure line of C II, the J = 9 --> 8, 12 --> 11, and 17 --> 16 lines of (CO)-C-12, and the J = 9 --> 8 rotational transition of (CO)-C-13 in the molecular cloud and photodissociation region (PDR) associated with NGC 3576. The line profiles were fully resolved using a heterodyne spectrometer with better than 1 km s(-1) resolution. The high-J CO emission arises from a spatially compact region near the infrared peak that is characterized by a kinetic temperature near 150 K and a density n(H2) greater than or similar to 5 x 10(5) cm(-3). The (CO)-C-12 J = 9 --> 8 line is found to be optically thick and arises from a more extended, cooler region with T-kin similar to 60 K. The increase in excitation temperature with the rotational level of CO suggests that the ionizing source is located behind much of the molecular cloud. Less than 1% of the molecular cloud material is found in the warm PDR and cloud interface region. The C 11 fine-structure line emission is intense over more than 4' x 4' and shows a central ''self-absorption'' feature at many locations. This absorption may represent a cooler or less dense component of ionized gas associated with the foreground molecular cloud.