Inner-valence states of CO⁺between 22 eV and 46 eV studied by high resolution photoelectron spectroscopy and ab initio CI calculations

Abstract

Photoionization of the CO molecule and inner-valence states of CO" between 22 and 45 eV have been studied by means of photoelectron spectroscopy using both synchrotron radiation and He ii radiation. Vibrational structure has been resolved in many bands up to 45 eV. CASSCF (complete active space self-consistent field) and MRCI (multireference configuration interaction) calculations of potential curves in the 22-30 eV range have been perfonned and these have been used to predict vibrational levels and Franck-Condon factors. In this energy range three valence states, D 'IT, 3'E' and 3% have been identified, and spectroscopic constants have been determined for the first two of these. Above 30 eV, all valence slates have been found to be repulsive. In addition to the broad bands expxted for these slates, several progressions of narrow lines are observed most probably reflecting transitions to Rydberg states.P Bultzer et a1 a1 (1994). At higher energies, above approximately 20 eV, the number of states increases quickly due to significant many-electron effects and this leads to a breakdown of the independent-particle molecular orbital approximation. The 3u-' hole state is split into a manifold of ' Z ' stales (Okuda and

Vibrational branching ratios in the photoelectron spectra of N2 and CO: interference and diffraction effects

“…As can be seen, both potentials are nearly identical in the vicinity of the energy minimum, thus suggesting that a Morse description of core-hole states for which standard CASSCF-MRCI calculations are not so easy to perform is accurate enough. For the ground state of the neutral and the cation, as well as for the lowest excited (valence) states of the cation, our calculated potential energy curves are in very good agreement with the ones previously reported in the literature 7,60,65,114,120,[126][127][128][129][130][131][132][133][134][135][136][137][138][139][140] .…”

Time-resolved studies of interatomic Coulombic decay

“…As it is known that the potential energy surfaces of these states are typically steeply repulsive (see e.g. [37]) two competing scenarios arise: firstly, the excited molecule dissociates, thus prohibiting ICD to occur or, secondly, ICD outpaces the dissociation stabilizing the molecule. As ICD was identified in the coincidence measurement, it was shown, that ICD occurs prior to a possible dissociation, i.e.…”

Vibrational branching ratios in photoionization of CO and N2

“…The current investigation addresses this issue by determining CO ϩ (B 2 ⌺ ϩ )v ϩ ϭ1/v ϩ ϭ0 vibrational branching ratios over a wide energy range for comparison with those of N 2 ϩ (B 2 ⌺ u ϩ ). While there has been enormous effort expended in understanding the VUV spectroscopy and photoionization dynamics of CO, [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] none has dealt with vibrationally resolved measurements over a wide range of energy ͑i.e., Ͼ100 eV͒. Previous work, 1,2,4,6 in conjunction with results from the current study, demonstrate that molecular aspects of the ionization dynamics emerge far from threshold.…”