Vacuum ultraviolet light emission from low-pressure hydrocarbon-oxygen flames

Abstract

The complete vacuum ultraviolet emission spectrum of hydrocarbon-oxygen flames has been measured by working at low pressure to reduce self-absorption and collisional de-excitation. The spectrum is emitted by flames of C 2 H 2 , C 2 H 4 , C 3 H 8 , and CH 4 with approximately the same intensity distribution, but with intensity diminishing in the order given. All the bands correlate with known bands of the CO fourth positive system, and transitions arising from the first seven vibrational levels of the upper state with excitation energies of 185 to 213 kcal/mole have been observed. Two series of quantitative measurements of the emission spectrum have been made for comparison with measurements of chemi-ionization by a Langmuir probe and total collection, respectively. The chemiluminescence arising from CH, OH, C 2 , and possibly CHO as well as the (CO) (O) continuum have also been measured. No evidence of a chemical mechanism linking any of the measured quantities could be found.