title: Heterodyne spectroscopy of the 158 micron C II line in M42.
abstract: We have obtained velocity-resolved spectra of the 12C II 157.8 microns 2P3/2-2P1/2 fine structure line in the M42 region of Orion.  Observations at 0.8 km s-1 resolution with a laser heterodyne spectrometer show multiple velocity components in some locations, with typical linewidths of 3-5 km s-1.  Spectra of theta 1C and BN-KL also show weak emission from the F = 2-1 hyperfine component of the equivalent 13C II line.  From the observed 12C II/13C II line intensity ratios, we deduce that the 12C II emission is optically thick with tau approximately 5 at both positions.  Excitation temperatures of 128 K and 90 K, together with column densities of approximately 1 x 10(19) cm-2 and approximately 4 x 10(18) cm-2, are derived for theta 1C and BN-KL, respectively.
authors.affiliation: Space Sciences Laboratory, University of California, Berkeley, USA.
authors.forename: R T
authors.initials: RT
authors.lastname: Boreiko
authors.forename: A L
authors.initials: AL
authors.lastname: Betz
authors.forename: J
authors.initials: J
authors.lastname: Zmuidzinas
mesh_terms: D001256:Astronomy / Q000379:methods*; D002244:Carbon / Q000032:analysis*; D005118:Extraterrestrial Environment; D008962:Models, Theoretical; D013057:Spectrum Analysis / Q000379:methods*; D013696:Temperature
chemical_list: D002244:Carbon