Lifetime Measurements of the [ITAL]E[/ITAL] [TSUP]1[/TSUP]Π, [FORMULA][F]v=0[/F][/FORMULA] and [FORMULA][F]v=1[/F][/FORMULA] States of [TSUP]12[/TSUP]C[TSUP]16[/TSUP]O, [TSUP]13[/TSUP]C[TSUP]16[/TSUP]O, and [TSUP]13[/TSUP]C[TSUP]18[/TSUP]O

In a laboratory investigation using tunable picosecond lasers in a pump-probe configuration, lifetimes of the E 1 Π, v =0 and v =1 states of CO are experimentally determined. For E 1 Π, v =1, the lifetime is found to vary significantly for the isotopomers. Combining the data with existing oscillator strengths, predissociation probabilities within the range of 93.6%-98.6% result for 12 C 16 O, 13 C 16 O, and 13 C 18 O in the case of the E 1 Π, v =1 state, which is the state that predominantly influences the isotopic fractionation of CO in interstellar clouds.