Electron affinity evaluation from negative ion mass spectrometry data.

Naphthoquinone (NQ), eleven of its hydroxyl-derivatives, pyromellitic diimide (PMDI), anthraquinone (AQ), azobenzene (AB) and phthalimide (PTI) were investigated by means of Negative Ion Mass Spectrometry (NIMS). All molecules under investigation, except PTI, form long-lived (a>10 s) molecular anions in the 0-2 eV energy range. NI lifetime measurements by means of a modified NIMS instrumentation can provide quantitative data of Electron Affinity (EA). A simple Arrhenius approximation seems to be adequate to describe the process of electron detachment from molecular anions.