Recently, a technique has been demonstrated which allows the measurement of
metastable lifetimes in neutral molecules of up to 10(-3) s [J. Chem. Phys
. 110, 6319 (1999)]. The present article extends the method by two orders-o
f-magnitude to molecular lifetimes as long as 10(-1) s. Using the CO metast
able a (3)Pi state, lifetimes of eight rovibrational a (3)Pi(upsilon = 3,Oh
m,J) levels were measured. Within their experimental error of 30%, these li
fetimes agree with previous theoretical predictions [J. Chem. Phys. 110, 63
19 (1999)]. The presented technique is suggested for identification of mole
cular quintet states, in particular the CO a " (5)Pi state. (C) 2000 Americ
an Institute of Physics. [S0021-9606(00)00512-2].