Chlorine K shell photoabsorption spectra of gas phase HCl and Cl2 molecules

Abstract

High resolution photoabsorption spectra of HC1 and C12 have been measured near the chlorine K edge in the 2810-2850eV photon energy range. Below the C1 K edge, the strongest resonance is interpreted as a simple core excitation into the unoccupied a* valence orbital for both molecules, leading to a markedly repulsive state. Higher resonances due to low lying Rydberg states, are observed in both systems, but with a larger oscillator strength for HC1 as compared to C12. In C12, the o-* orbital is deep enough to avoid any mixing with Rydberg orbitals. In HC1, we observe the dipole forbidden C1 ls--,4s transition which denotes a strong 4s-4p hybridization. Above the C1 K edge, the multiplet features seen for HC1 are analysed in terms of doublecore-valence excited vacancy states. In Ct2, their counterpart are found very close to the ionization threshold because of the deep a* orbital and possibly because the excited core and valence electrons originates either from the same atomic site or from different ones.

KL double core hole pre-edge states of HCl

“…2. Akin to the work of Püttner et al, 8 where the 1s À1 2p À1 nc photoelectron spectrum of Ar was found to resemble a 1s À1 photoabsorption spectrum, we expect for the case of HCl 22 Rydberg states close to threshold and states connected with excitations into the s* valence orbital in the lower energy region, where the latter is also cooperated by our MCSCF calculations.…”

X-Ray Scattering and Fluorescence From Atoms and Molecules

“…The absorption spectrum is plotted in Fig. 24 and is similar to the spectrum analyzed by Bodeur et al 99 The characteristic XFS measured above the ionization threshold is plotted in the bottom of Fig. 25 and shows partiallyresolved peaks due to the 2p g , 2p u , and 5s g valence MOs.…”

Multireference X-ray emission and absorption spectroscopy calculations from Monte Carlo configuration interaction

“…For these absorption results, methods based on DFT with large basis sets have found 533.89 eV for water [7] while for CO the energies were 534.21 eV [7], 533.0 eV [8] and, depending on the functional, 535.1 eV to 536.1 eV [6]. Table 5 MCCI X-ray absorption energies and oscillator strengths at c min = 5 × 10 −4 with a 6-311G** basis for the lowest energy core hole in the neutral molecule compared with experimental results [30,31,32,33,34] Table 6 displays how all of the core-hole states for the neutral molecules appear to have multireference character. This continues in the core-hole state of B 1 symmetry for carbon monoxide (M R = 0.71).…”

“…MCCI X-ray absorption energies and oscillator strengths at c min = 5 × 10 −4 with a 6-311G** basis for the lowest energy core hole in the neutral molecule compared with experimental results[30,31,32,33,34].…”