This mechanism is usually called "chemi-ionization
" [8, 9], "chemical ionization" , "flame ionization"  or "flame front" , and it corresponds to the first peak on the ion signal, after the ignition, as it can be seen in Figure 2.
Given the large discrepancy between ion concentrations estimated from experimental data and equilibrium calculations, Calcote and King concluded that "ions are produced not by thermal processes but by chemi-ionization or events similar to those using abnormal electronic excitation in flames.
These equilibrium computation results validate the conclusions of Calcote and King, namely, that for a laboratory flame, thermal equilibrium does not exist between species in the flame front and that ions are produced not by thermal process but by chemi-ionization. The equilibrium computations under engine-like conditions showed a marked increase in the ion concentration of [H.sub.3][O.sup.+] with and without the assumption of LTE.