Inner-valence shell photoionization of Ar2, Ar3, Kr2, and Kr3

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Abstract
The inner‐valence shell photoionizationspectra (420<λ<500 Å) of Ar2, Ar3, Kr2, and Kr3 have been obtained with a molecular beam apparatus using synchrotron radiation from the VUVstorage ring at the National Synchrotron Light Source. The photoionizationspectra exhibit regular series of window resonances which are closely associated with the m s→n pRydberg series in atomic Ar(m=3) and Kr(m=4). Vertical ionization potentials of the lowest ionic state in the molecular m s regions were obtained by series extrapolation and these were used to estimate the well depths in the Franck–Condon region and dissociation energies. Assignments of the observed Rydberg transitions were made by analogy with similar excitations in He2 and the group II and II B metal dimers. For Ar+ 2 and Kr+ 2, the observed structure is tentatively assigned to 1 u (1Π u ) and O+ u (1Σ u +) states which correlate with the ‘‘promoted’’ ndπ g and n dσ g series. Plausible assignments for the trimer spectra are also discussed.