Abstract
An apparent selective excitation to the ν' = 1 level of the CH 3900 Å (2Σ- → 2Π) system occurs in hydrogen flames containing small amounts of organic compounds since the (1, 0) and (1, 1) bands are abnormally strong. This is accompanied by a suppression of the usual predissociation in this system. An additional band of this system, the (1, 2) at 4494.5 Å has been observed for the first time.
The suppression of the CH predissociation is interpreted as showing that conditions in hydrogen flames approach thermal equilibrium. The appearance of the CH predissociation in normal flames indicates that the excitation is not thermal.