First-Principles Calculations of the Energy and Width
of the <sup>2</sup>A<sub>u</sub> Shape Resonance in <i>p</i>‑Benzoquinone: A Gateway State for Electron Transfer
- Publication date
- Publisher
Abstract
Quinones are versatile biological
electron acceptors and mobile
electron carriers in redox processes. We present the first ab initio
calculations of the width of the <sup>2</sup>A<sub>u</sub> shape resonance
in the <i>para</i>-benzoquinone anion, the simplest member
of the quinone family. This resonance state located at 2.5 eV above
the ground state of the anion is believed to be a gateway state for
electron attachment in redox processes involving quinones. We employ
the equation-of-motion coupled-cluster method for electron affinity
augmented by a complex-absorbing potential (CAP-EOM-EA-CCSD) to calculate
the resonance position and width. The calculated width, 0.013 eV,
is in excellent agreement with the width of the resonant peak in the
photodetachment spectrum, thus supporting the assignment of the band
to resonance excitation to the autodetaching <sup>2</sup>A<sub>u</sub> state. The methodological aspects of CAP-EOM-EA-CCSD calculations
of resonances positions and widths in medium-sized molecules, such
as basis set and CAP box size effects, are also discussed