Inner-valence states of O2+ and dissociation dynamics studied by threshold photoelectron spectroscopy and a configuration interaction calculation

Abstract

High-resolution threshold photoelectron spectroscopy has been used to study O2 in the 24–50 eV photon energy region, where several broad bands with superimposed fine peaks are observed. Theoretical calculations on the basis of the state-averaged complete-active-space self-consistent-field method followed by the second order configuration interaction method reproduce well the general band features of the threshold photoelectron spectrum, enabling us to assign the bands to inner-valence O2+ states. Dissociation products formed from the inner-valence O2+ states have been investigated by threshold photoelectron–photoion coincidence spectroscopy and their dissociation dynamics discussed with reference to the theoretical potential energy curves.

Observing the Creation of Electronic Feshbach Resonances in Soft X-ray–Induced O 2 Dissociation

“…The known potential energy curves of O 2 + in the inner-valence regime are all highly repulsive (27). Therefore, unless autoionization into quasi-bound states on the X curve has already taken place (if spin-allowed), the potential energy of O 2 + would be expected to drop below all O 2 2+ curves.…”

Nonadiabatic transition in the dissociation process from inner valence states of O2+

“…1͒ versus the fragment O ϩ kinetic energy at various ionization energies, which correspond to those of the previous experimental TPEPICO spectra. 1 The dissociation limits shown in the figures are the same as those of the previous ones ͑see the Table I in Ref. 1͒.…”

“…In a previous paper 1 we reported a study of electronic structures of inner valence states of O 2 ϩ and the dissociation process from the states, where we succeeded to explain theoretically the general feature of an observed threshold photoelectron spectrum using potential energy curves obtained by second-order configuration interaction ͑SOCI͒ calculations, and gave assignments of the inner valence O 2 ϩ states in the 24 -45 eV photon energy region. The calculated potential energy curves have also predicted qualitatively dissociation products from the states given by using threshold photoelectron-photoion coincidence ͑TPEPICO͒ spectroscopy.…”

“…The calculated potential energy curves have also predicted qualitatively dissociation products from the states given by using threshold photoelectron-photoion coincidence ͑TPEPICO͒ spectroscopy. 1 There remained, however, some questions as to the origins of the dissociation fragment formation of the L 3 limit, O ϩ ( 2 D)ϩO( 3 P), of which kinetic energy spectra were observed by TPEPICO at incident photon energy ranges of 32.37-33.89 eV and 37.32-41.34 eV. From the calculated adiabatic potential energy curves and theoretical intensities of the inner valence O 2 ϩ states, it remains an uncertainty as to the paths into the L 3 fragment formation even if we consider some nonadiabatic transitions in the potential energy curves.…”

“…The calculations were performed on the basis of the Zhu-Nakamura theory 2 by using the previous adiabatic potential energy curves which did not include any Rydberg states. 1 At a given ionization energy E, a normalized multichannel transition probability into the nth dissociation limit I n (E) was calculated with the following equations: …”