He I Ultraviolet Photoelectron Spectroscopy of Benzene and Pyridine in Supersonic Molecular Beams Using Photoelectron Imaging

Abstract

We performed He I ultraviolet photoelectron spectroscopy (UPS) of jet-cooled aromatic molecules using a newly developed photoelectron imaging (PEI) spectrometer. The PEI spectrometer can measure photoelectron spectra and photoelectron angular distributions at a considerably higher efficiency than a conventional spectrometer that uses a hemispherical energy analyzer. One technical problem with PEI is its relatively high susceptibility to background electrons generated by scattered He I radiation. To reduce this problem, we designed a new electrostatic lens that intercepts background photoelectrons emitted from the repeller plate toward the imaging detector. An energy resolution (ΔE/E) of 0.735% at E = 5.461 eV is demonstrated with He I radiation. The energy resolution is limited by the size of the ionization region. Trajectory calculations indicate that the system is capable of achieving an energy resolution of 0.04% with a laser if the imaging resolution is not limited. Experimental results are presented for jet-cooled benzene and pyridine, and they are compared with results in the literature.

Benchmark ofGWmethods for azabenzenes

“…96 and references therein). Both PBE and PBEh predict the HOMO to be an n-orbital and the HOMO-1 and HOMO-2 to be π-orbitals.…”

“…This demonstrates again that the differences between G 0 W 0 calculations based on different starting points are by and large independent of the basis set size. 96 Illustrations of the frontier orbitals are also shown. Figure 5: Spectra of pyridine, calculated with DFT and G 0 W 0 , broadened by a 0.3 eV Gaussian, compared to gas phase PES.…”

“…Figure 5: Spectra of pyridine, calculated with DFT and G 0 W 0 , broadened by a 0.3 eV Gaussian, compared to gas phase PES. 96 Illustrations of the frontier orbitals are also shown. Figure 6: Spectra of pyridazine, calculated with DFT and G 0 W 0 , broadened by a 0.3 eV Gaussian, compared to gas phase PES.…”

“…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.…”