The N2 C 3PI(u). lifetime was measured by laser-induced fluorescence (
LIF) in a low-density plasma. To take account of radiation trapping ef
ects, the lifetime was measured as a function of LIF signal amplitude,
which is also a measure of the N2 B 3PI(g) density. To first order, r
adiation trapping is linearly proportional to B-state density. By extr
apolating the data to zero density, values around 40.5+/-2 nsec were f
ound for the C-state lifetime.