Shape resonances in slow electron scattering by aromatic molecules. I. Anthraquinone derivatives
✍ Scribed by Nail L. Asfandiarov; Alexey I. Fokin; Vladimir G. Lukin; Ekatherina P. Nafikova; Gennadii S. Lomakin; Vladimir S. Fal’ko; Yuri V. Chizhov
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 139 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0951-4198
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✦ Synopsis
A series of anthraquinone (C 14 O 2 H 8 ) derivatives has been studied by means of electron capture negative ion mass spectrometry (ECNI-MS), photoelectron spectroscopy (PES), and AM1 quantum chemical calculations. Mean lifetimes of molecular negative ions M ÀÁ (MNI) have been measured. The mechanism of long-lived MNI formation in the epithermal energy region of incident electrons has been investigated. A simple model of a molecule (a spherical potential well with the repulsive centrifugal term) has been applied for the analysis of the energy dependence of cross sections at the first stage of the electron capture process. It has been shown that a temporary resonance of MNI at the energy $0.5 eV corresponds to a shape resonance with lifetime 1-2Á10 À13 s in the f-partial wave ( = 3) of the incident electron. The next resonant state of MNI at the energy $1.7 eV has been associated with the electron excited Feshbach resonance (whose parent state is a triplet np* transition). In all cases the initial electron state of the MNI relaxes into the ground state by means of a radiationless transition, and the final state of the MNI is a nuclear excited resonance with a lifetime measurable on the mass spectrometry timescale.