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Vibrationally resolved spectra have been obtained for the lowest-lying cationic states X(2B1), A(2A1) and B(2B2) of the water molecule reached after participator resonant Auger decay of core-excited states. The angular distribution has been measured for the first four vibrational components of the X-state in the photon energy regions including the O1s->4a1 and the O1s->2b2 core excitations, and for different portions of the vibrational envelope of the B-state in the photon energy region including the O1s->2b2 core excitation. For the X-state, a large relative spread in beta values of the different vibrational components is observed across both resonances. For the B-state, a very different trend is observed for the high binding energy side and the low binding energy side of the related spectral feature as a function of photon energy. A theoretical method based on the scattering K-matrix has been used to calculate both the photoabsorption spectrum and the beta values, by taking both interference between direct and resonant photoemission and vibrational/lifetime interference into account. The numerical results show qualitative agreement with the trends detected in the experimental values and explain the conspicuous variations of the beta values primarily in terms of coupling between direct and resonant photoemission by interaction terms of different sign for different final vibrational states.

An interference quenching of the m = 1 final state vibrational line in the resonant Auger decay of N 1s* core-excited N2 is observed and analyzed. The intensity ratio between the m = 1 and m = 0 vibrational levels of the X 2 final state shows a surprising nonmonotonic variation as a function of frequency detuning, going through a minimum with a complete suppression of m = 1. We have developed a simple model which indicates a linear relation between the value of the detuning frequency for this minimum and the equilibrium bond distance of the core-excited state. This implies the possibility of determining the equilibrium bond distances for core-excited states to a high degree of accuracy. Simultaneously with the simple model we present a strict theory of the studied effect. This strict theory allows us to explore the accuracy of determining the bond length of the core-excited state from resonant Auger spectra. We obtain a weak influence of the core-hole lifetime on the determined bond length, whereas the number of intermediate vibrational states accounted for in the numerical simulations seems to be quite important.

International audience; An interference quenching of the v''=1 vibrational line in the resonant Auger decay of N 1s -> Pi* core-excited N2 is observed and analyzed. The intensity ratio between the v''=1 and v''=0 vibrational levels of the X2Sg+ final state shows a surprising nonmonotonous variation as a function of frequency detuning, going through a minimum with a complete suppression of v''=1. We have developed a simple model which shows a linear relation between the value of the detuning frequency for this minimum and the equilibrium bond distance Rc0 of the core-excited state. A new way is thus established of determining the equilibrium bond distance for the core-excited state with a precision dRc0

The O 1s" border=0 src="http://ojps.aip.org/stockgif2/rarr.gif"* transition below the O K-edge in O2 has been investigated by absorption, constant ionic state (CIS) experiments, and extensive configuration interaction calculations. CIS scans of the three lowest-lying final states reached in resonant Auger decay provide a wealth of information on energy range, symmetry, and spin multiplicity of the intermediate states with * character. We conclude that the identification of only two exchange-split components is inadequate because a complex manifold of states with * character exists with no unique energy difference between related states.

9 pages; We report new measurements of the decay of the core-excited O 1s–1πg 3Πu state in molecular oxygen under Auger resonant Raman conditions. The spectral features are interpreted with the aid of ab initio calculations using standard lifetime-vibrational interference, and in some cases, employing a model in which the bond-length dependence of the Auger transition rates is taken into account. By analyzing a series of Auger-decay spectra using different excitation energies, several instances of fixed kinetic energy are pointed out in the spectra; the nondispersive behavior arises from the decay between two potentials that are essentially parallel.