Lifetime of electronically excited NO2: Evidence for a short-lived state

The lifetime of one spin component of the 524 rotational level of some vibrational level of B2 symmetry of the 2B2 electronic state of NO2 has been measured by observing the linewidth of the microwave-optical double resonance spectrum of that state. The lifetime determined from the zero power, zero pressure linewidth extrapolation is less than 3.39 ± 0.36 μsec and is over an order of magnitude shorter than that usually measured in NO2. This indicates that at least some electronically excited levels of NO2 have lifetimes approaching those calculated from the integrated absorption coefficient.