Experimental and theoretical study of resonant core-hole spectroscopies of gas-phase free-base phthalocyanine

Abstract

We studied N $1s^{-1}$ inner-shell processes of the free base Phthalocyanine molecule, H$_2$Pc, in the gas-phase. This complex organic molecule contains three different nitrogen sites defined by their covalent bonds....

Influence of Selective Carbon 1s Excitation on Auger–Meitner Decay in the ESCA Molecule

“…This is not guaranteed by density functional theory based methods that optimize the cation wave functions with an overlap criterion. 11 Figure 2a shows that the theory correctly identifies peaks E, D, and C as the major contributions and correctly describes the relative shape across the spectrum. This result suggests that the ezDyson method is a promising approach for the challenging simulation of mid-sized (>10 atoms) polyatomic molecular photoelectron spectra, with few examples in the literature.…”

“…Several studies have explored the site selectivity in the resonant AM decay following core excitation, based on factors such as the chemical environment, the energy of the excited state, or its symmetry, benchmarked by the experiments outlined in refs − . A recent study on HNCO by Holzmeier et al found only minor differences in resonant AM spectra for excitation at C, N, or O sites, or for different intermediate states, while de Moura et al found that excitation at different nitrogen sites in phthalocyanine leads to visible changes in the spectra . These examples highlight the complexity of resonant photoemission and that there are often subtle factors which determine the probability for populating final valence states even when site selectivity is possible.…”

“…Methods neglecting the continuum by an electron population analysis add no additional cost to the electronic structure calculation and are attractive for larger systems and for probing ultrafast dynamics with time-resolved AM decay . Recently, de Moura et al successfully interpreted the large trans-H 2 -phthalocyanine molecule decay using a population analysis approach . Here we use the method developed by Mittani et al, where the AM intensity is approximated by the electronic populations of the molecular orbitals on the core–hole atom in the core-excited state wave function and is described in detail elsewhere. − This approach is similar to the one employed by de Moura et al; however, it in neglects the lifetime interference contributions which were found to have a minor influence on the results …”

“…However, our results show that EOM-CCSD sufficiently describes the electron-correlation effects in photoionization processes for all the cation states in the molecule. This is not guaranteed by density functional theory based methods that optimize the cation wave functions with an overlap criterion …”

“…34−36 This approach is similar to the one employed by de Moura et al; however, it in neglects the lifetime interference contributions which were found to have a minor influence on the results. 11 In order to correctly account for the competing coreexcitation and direct valence ionization processes produced by complementary levels of theory, the separate theoretical contributions were normalized to 1. Then the resonant AM spectra were scaled by a factor derived from the ratio of the total valence ezDyson photoelectron cross section and the EOM-CCSD core-excitation cross section from a previous calculation.…”