Photodetachment and de-excitation of excited NO2−

The photodetachment of excited NO2− formed by charge exchange of O− and O2− with NO2 has been studied at photon energies of 1.97 to 2.34 eV, below the electron affinity of NO2 (2.36±0.10 eV). These data indicate that the subthreshold photodetachment takes place from excited vibrational levels of the NO2− ground electronic state, which are populated by the ion–molecule reactions producing this species. De-excitation of the excited NO2− is observed in collisions with O2 and CO2 molecules with apparent rates in the range of 10−12 cm3/sec and with NO2 molecules at a rate of nearly 10−9 cm3/sec. The absolute photodetachment cross section of nascent NO2− is determined at three photon energies. No evidence is found for a structural (peroxy) isomer of this ion.