Reactions of C(³P) and C⁺(²P) with NH₃ studied spectroscopically at hyperthermal energies

Chemiluminescent reactions of C(3P) atoms and C+(2P) ions with NH3 were investigated in the 12-1000 eVLab (7-586 eVCM) energy range, using a beam/gas arrangement. The fast carbon atoms were generated from C+(2P) ions by near-resonant charge transfer with CCl4. The reaction products NH(A 3Π), CN(B 2Σ+), and CH(A 2Δ) were studied by means of the NH(A-X), CN(B-X), and CH(A-X) emission spectra at 1.4 and 0.35 nm fwhm resolution. Besides, traces of NH(c1Π - a 1Δ), CH(B 2Σ- - X 2Π), and Balmer line emission were also observed. The reactions were classified as follows: (a) CH(A) is formed by exchange reactions, which are assisted by a hard-sphere-collision mechanism at high energies to moderate the kinetic energy; (b) NH(A) and NH(c) originate at low energies from substitution reactions, and NH(A) also results from collisional dissociation at high energies; (c) CN(B) is formed (only at low energies) via a long-lived [C-NH3]+ complex. Detailed evidence for these assignments came from the observed spectra, which were analyzed by means of a computer simulation, as well as from measurements of the energy-dependent relative cross sections