Internal conversion as the main stabilization mechanism for long-lived negative molecular ions

The temperature dependence of the mean lifetime of Ph–N=N–Ph$^-$ azobenzene negative molecular ions on the captured electron energy is studied with a static mass spectrometer by the method of resonance electron capture. A family of respective experimental dependences is calculated accurate to 2–10%. It is shown that the molecular anions in the epithermal electron energy range can be stabilized through internal conversion, namely, a series of fast radiationless transitions without change in the multiplicity.