We have attempted to form ethylidyne (CCH3) by the multiphoton dissociation of 1,1,1-tribromoethane. A neutral intermediate is formed that will react with a ground-state oxygen atom to form a chemi-ion with a mass-to-charge ratio of 43. By analogy with the known behavior of CH, we propose that the observed chemiions are formed by reaction 1, CCH3 + O(P-3) --> CH3CO+ + e(-). Using the rate of formation of chemi-ions as a surrogate for the ethylidyne concentration, rate constants for CCH3 could be measured. Ethylidyne reacts rapidly with O-2 and NO, with rate constants comparable to those observed for CH(a(4) Sigma(-)). The ethylidyne does not react with N2O or N-2, again similar to what is observed for CH(a(4) Sigma(-)) and in sharp contrast to the behavior of ground-state CH(X(2)II). Guided by its kinetic behavior and by previous ab initio calculations, we conclude that the ethylidyne is in its metastable quartet state, CCH3((a) over tilde(4)A(2)).