Multiplet splitting in 1s hole states of molecules

Abstract

The binding energies of selected C, N, O, and F 1s electrons in six paramagnetic molecules were measured by x-ray photoemission. A splitting of 1.934(41) eV was observed in the N(1s) line of NF2, and several other splittings were remeasured or obtained by fitting asymmetric but unresolved lines. Use of the Mg Kα12 doublet profile in fitting improved the fits markedly. A multiplet hole theory was developed to predict the final-state multiplet splitting. It uses atomic exchange integrals, INDO calculations on an ``equivalent-core'' final state to obtain spin densities, and Van Vleck's Theorem to account correctly for multiplicity. It gives results in very good agreement with experiment, and it can be used for larger molecules. During photoemission spin density migrates away from the 1s hole in most cases, and electronic charge flows toward this hole, affecting both the 1s splitting and the 1s binding energy. The lower N(1s) binding energy in di-t -butylnitroxide than in NO arises from electron flow to nitrogen from the t -butyl group during photoemission. This inductive effect is closely related to the ease of substitution of nucleophilic groups in unimolecular reactions with tertiary alkyl halides, a phenomenon that must also be understood in terms of final- (or transition-) state properties, rather than simply in terms of the initial state. Inequivalent fluorines in N2F4 were identified by an unresolved doublet structure in the F(1s) peak.

Symmetry- and multiplet-resolved N1sphotoionization cross sections of theNO2molecule

“…[40]]. At the same geometry the (aug-cc-pVTZ) SCF energy of the ground state is −204.105 612 a.u., giving a singlet-triplet spacing of about 0.78 eV, which compares remarkably well with the experimental XPS result of 0.70 eV [41].…”

“…The 1 A 1 and 3 A 1 N 1s −1 partial cross sections show maxima at the photon energies of 416.3 and 415.9 eV, respectively. Given that the ionization potentials for the 1 A 1 and 3 A 1 N 1s −1 states are 413.3 and 412.6 eV, respectively [41], the energy difference of the two multiplet thresholds thus is 0.7 eV, whereas the energy difference of the shape resonance for the two multiplet components is 0.4 eV. This means that the potential in the 1 A 1 channel is somewhat more attractive than that in the 3 A 1 channel.…”

Hyperfine Interactions and ESCA Data

“…[17] have shown theoretically that in molecules the host-atom spin-density is different in the initial and final states. Typical results for 0 , N0r and NF are shown in Fig.…”

Core Shell Investigation of 2-nitroimidazole

“…A first qualitative assignment of these XPS spectra is suggested by the energy positions of the main XPS bands for imidazole (Apen et al, 1993; Thomason et al, 2015) and nitrogen dioxide (Davis et al, 1973; Jolly et al, 1984), i.e., the building blocks of the nitroimidazole molecule. The core binding energies (BE) of these building blocks are represented by the vertical bars in Figure 1, and the corresponding values are reported in Table 1, together with the binding energies of 4- and 5-NIM isomers from Feketeová et al (2015a).…”

“…Diagram of the binding energies (black) and of the lowest (LUMO) excitation energies (red) at the O, N, and C K edges and at the valence shell (Kimura, 1981; Schwell et al, 2008; Cartoni et al, 2018), for nitrogen dioxide (Davis et al, 1973; Au and Brion, 1997; Jayawardane et al, 2001) (left), 2NIM (center) and imidazole (right) (Apen et al, 1993; Thomason et al, 2015) molecules.…”