Hybrid density-functional theory calculations of near-edge x-ray absorption fine-structure spectra : Applications on benzonitrile in gas phase

• The experimental N(1s) near-edge x-ray-absorption fine-structure spectrum of the benzonitrile molecule in the gas phase shows well separated double peaks with different vibrational profiles. Hybrid density-functional theory calculations reveal that such a separation is a result of the conjugation effect on the nitrogen 2p orbitals and the double spectral peaks can be assigned as the N(1s)-pi* out-of-plane and in-plane resonances. The vibrational profiles have been analyzed using a combined transition state theory and linear coupling model. Each profile consists of two different vibrational progressions corresponding to stretching modes and a broad continuum of bending excited states. The use of transition state theory allows identifying the dynamics of the N 1s core excitation. It is found that upon core excitations the C-N bond of the benzonitrile molecule can go from initial linear to final bent structures through different paths. The calculated spectrum is in excellent agreement with experiment.

Nyckelord

equivalent-cores approximation

electron binding-energies

polyatomic-molecules

photoelectron-spectroscopy

vibrational structure

chemical-shifts

hydrocarbons

ionization

exchange

model

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)