Benchmark Dyson Orbital Study of the Ionization Spectrum and Electron Momentum Distributions of Ethanol in Conformational Equilibrium

Abstract

An extensive study, throughout the valence region, of the electronic structure, ionization spectrum, and electron momentum distributions of ethanol is presented, on the ground of a model that focuses on a mixture of the gauche and anti conformers in their energy minimum form, using weight coefficients obtained from thermostatistical calculations that account for the influence of hindered rotations. The analysis is based on accurate calculations of valence one-electron and shakeup ionization energies and of the related Dyson orbitals, using one-particle Green's Function (1p-GF) theory in conjunction with the so-called third-order Algebraic Diagrammatic Construction scheme [ADC(3)]. The confrontation against available UPS (HeI) measurements indicates the presence in the spectral bands of significant conformational fingerprints at outer-valence ionization energies ranging from approximately 14 to approximately 18 eV. The shakeup onset is located at approximately 24 eV, and a shoulder at approximately 14.5 eV in the He I spectrum can be specifically ascribed to the minor anti (C(s)) conformer fraction. Thermally and spherically averaged Dyson orbital momentum distributions are computed for seven resolvable bands in model (e, 2e) ionization spectra at an electron impact energy of 1.2 keV. A comparison is made with results obtained from standard (B3LYP) Kohn-Sham orbitals and EMS measurements employing a high-resolution spectrometer of the third generation. The analysis is qualitatively in line with experiment and reveals a tremendously strong influence of the molecular conformation on the outermost electron momentum distributions. Quantitatively significant discrepancies with experiment can nonetheless be tentatively ascribed to strong dynamical disorder in the gas phase molecular structure.

Ionization of pyridine: Interplay of orbital relaxation and electron correlation

“…The Dyson orbitals can be used for studies of various ionization related phenomena, [67][68][69][70][71] as well as for the visualization of the results of the Green's function calculations. 49,53 In the present study we employ Dyson orbitals to analyze the ADC(3) results for pyridine.…”

Theoretical study of molecular vibrations in electron momentum spectroscopy experiments on furan: An analytical versus a molecular dynamical approach

“…[40][41][42] Further physical phenomena that can strongly influence the recorded momentum distributions pertain to nuclear dynamics. Following Hajgató et al 43 or Deleuze et al, 44,45 it is useful to distinguish nuclear dynamics in the initial and neutral electronic ground state, comprising thermally induced conformational rearrangements [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] or pseudo-rotational motions, 61,62 from nuclear dynamics in the final ionized state, more specifically, geometrical relaxation, vibronic coupling interactions, and ultra-fast bond cleavages [43][44][45][63][64][65][66][67] induced by the ionization processes of interest.…”

Electron propagator theory: an approach to prediction and interpretation in quantum chemistry

“…Deleuze et al have made extensive use of electron propagator methods in studies of the electron binding energies of carbon clusters126–128 and polycyclic aromatic hydrocarbons 33,129,130. The same techniques have been applied successfully to electron momentum spectra 131–135. Ohno and coworkers136–138 have combined Penning ionization experiments with electron propagator calculations to obtain novel insights into chemical bonding.…”