Schematic energy diagram for argon atoms pointing out the main ionic, states accessible at the photon energies used in this study. On the right-hand side the adiabatic ionization potentials and the dissociation limits of argon dimers are presented to illustrate the possible energetic states of the fragments. The letters, “v” or “a,” refer to the vertical IPs and the adiabatic IPs (see text).
Partial dimer yield spectra of clusters of different sizes close to the atomic resonance. According to Ref. 2 the two observed features in the cluster can be assigned to the surface of bulk atoms in the clusters. The bottom spectrum is the ion yield spectrum from free argon atoms. The marker set under the atomic peak represents the maximum photon bandwidth used, which is about .
Ion time-of-flight spectra for argon clusters of an average size of atoms at energies of 236, 244.6, and . The spectra are normalized with respect to the total number of electrons (starts) and to the acquisition time, so the intensity of each peak reflects the partial cross section of each photoion multiplied with its detection probability.
The and photoion peaks from Fig. 3 are shown using a solid line. The scaling factor is given to compare the absolute peak height. The dashed line represents the line shape for the same ion measured in a double, triple, and quadruple ion-coincidence event [projection of spectra].
Sequence of processes leading to dimer and monomer fragments after inner-shell resonant excitation and inner-shell ionization. and represent the internal energy which can be left in the cluster with respect to the lowest dissociation limit of and .
Relative production of different species in coincidence according to the following notation: first ion; second ion. The enhancement of dimer production on resonance at confirms the observation made in the normalized mass spectra. It also shows that atomization of doubly-charged species is almost complete above the threshold.
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