Lifetime Measurements of Some Excited States of Nitrogen, Nitric Oxide, and Formaldehyde

An experimental method for measurement of short decay times of fluorescence (10—8—10—5 sec) from excited states of molecules is described. The method is applied to the transitions C3IIu—B3IIg (second positive) and B3IIg—A3Σu+ (first positive) of nitrogen and to the transitions A2Σ+—X2II (γ system) and B2II—X2II (β system) of NO. Direct measurement of the lifetime of the lowest singlet excited state of formaldehyde is reported. In some of the transitions, the dependence of lifetime on vibrational quantum number in the initial upper state were studied. The pressure dependence of the lifetimes was also investigated.