Infrared Emission Spectra of Flames 451

The infrared emission spectra of a hydrogen flame and' of a natural gas flame have been compared in the region from 1. 7p. to 24p.. Emission bands have been observed at 1.87p., 2.78p. , 4.37p., 6.20p., and 15p. that a re produced by molecules of H 20 and CO2• Another band at 3.316p. is attributed to methane. From 3.0p. to 3.8p. there are a number of rotational lines, some of which may be produced by OH and others by H 20 molecules. As the temperature of the flame was increased, the rotational lines became more intense. Five lines in the region from 3.4p. to 3.8p. agree clo ely in posit ion with the predicterl rotational lines of tbe P branch of the 2-->1 vibrational band of OH. These lines correspond to values of [( equal to 11, 12, 13, 14, and 15. Wave numbers of some of the observed rotational lines were found to show a good correspondence with predicted values for K equal to 11 tv 36, for lines extending from 9p. to 24p.. I n addi tion to this series of lines, t here are other lines that are produccd by the rotational states of H 20 molecu le. A discussion i included of t he various methods of observing name spectra.