Negative ions, molecular electron affinity and orbital structure of PAH molecules

What is it about?

Negative ions of polyarenes were generated in the gas phase in a mass spectrometer by low-energy electron bombardment, and long-lived molecular ions were detected. "Long-lived" means that they survive until mass spectrometric detection after several microseconds of drift along the mass spectrometer tube, but we demonstrated that molecular anions from different compounds have different lifetimes because of variation of excess-electron autodetachment. Autoneutralization lifetimes appeared to depend on molecular adiabatic electron affinity. The latter parameter of molecules is strongly dependent on the size and structure of molecules, thus being different even for structural isomers seemingly close in their shapes. By analyzing molecular orbital structures of isomeric compounds we made attempt to explain the couses of such variation of electron affinity among polycyclic aromatic hydrocarbons (PAH).

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Why is it important?

It seems that our article unsealed the old stratum of problems associated with misinterpretation of experimental data on the molecular electron affinity measured by different physico-chemical techniques (e.g. photoelectron spectroscopy of negative ions versus electron capture detector). Drs. Chen & Chen immediately proposed their unpublished data on adiabatic electron affinity (AEA) for 15 PAH molecules measured by means of electron capture detector, and assigned some earlier reported AEAs to the electron affinity of excited molecules (see Comment of these authors on our article by following this reference: DOI: 10.1002/rcm.8021).