Collision Energy Resolved Penning Ionization Electron Spectroscopy of Azines:  Anisotropic Interaction of Azines with He*(2³S) Atoms and Assignments of Ionic States

Abstract

Ionization of azines (s-triazine, pyridazine, pyrimidine, pyrazine, and pyridine) with He*(2 3 S) metastable atoms was studied by (collision-energy/electron-energy-resolved) two-dimensional Penning ionization electron spectroscopy. Collision energy dependence of the partial ionization cross sections (CEDPICS), which reflects interaction potential energy between the molecule and He*(2 3 S), showed anisotropic interaction around the molecules. Assignments of the Penning ionization electron spectra and ultraviolet photoelectron spectra were discussed on the basis of different behavior (positive or negative slope) of CEDPICS. Theoretically computed CEDPICS of s-triazine by classical trajectory calculations were found to be useful to confirm the assignment of the ionic states.

Benchmark ofGWmethods for azabenzenes

“…The n-π-π ordering is in agreement with high level wave-function and Green's function based calculations [113][114][115]122 and PES experiments. 97,[100][101][102] The PBE spectrum appears compressed with respect to experiment, yet the spacing between the n HOMO and the π HOMO-1 is too large. This may be explained by a shift of the n-orbital to higher energies as a result of the SIE associated with the nitrogen lone-pair.…”

“…For pyridazine (Figure 6), the assignment of the n-π-π-n character to the HOMO to HOMO-3, respectively, is motivated by PES experiments 97,100 and Green function based calculations. 115,116 PBE predicts a wrong orbital ordering of n-n-π-π and the spectral shape is distorted with the HOMO-2 being very close to the HOMO-1 instead of to the HOMO-3.…”

“…98,100,101,103,104,108,111,112,115,116 For both molecules, as for pyridazine, PBE underbinds the n-orbitals with respect to the π-orbitals, whereas HF overbinds the norbitals with respect to the π-orbitals. This leads to an incorrect orbital ordering and a distorted spectral shape.…”

“…They embody the basic physics of such systems including the strong correlation effects in aromatic π-systems 84,89,92 and the self-interaction effects introduced by the nitrogen lone pairs. 51,59 Another advantage of these systems is that they are well-characterized experimentally [93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108] and well-studied theoretically by high-level wavefunction and Green's function methods. 93,104,[109][110][111][112][113][114][115][116][117][118][119][120][121][122] We calculate the electronic structure of benzene, pyridine, and the diazines using: (i) semi-local and hybrid DFT (ii) G 0 W 0 , (iii) ev-scGW, (iv) scGW 0 , (v) scGW, and (vi) G 0 W 0 combined with the second-order exchange self-energy (2OX), as an attempt to go beyond the GW approximation.…”

Assessment of the performance of tuned range-separated hybrid density functionals in predicting accurate quasiparticle spectra

“…Experimental ionization energies in gas-phase for benzene 65 and pyrimidine 66 are denoted as dashed horizontal lines. Eigenvalues for which the experimental (and G 0 W 0 @CSP) energies are degenerate are represented by the same color.…”