Photoionization of argon, krypton and xenon clusters in the inner valence shell region

Photoionization of rare gas clusters in the innervalence shell region has b een investigated using threshold photoelectron and photoion spectrometers a nd synchrotron radiation. Two classes of states are found to play an import ant role: (A) valence states, correlated to dissociation limits involving a n ion with a hole in its innervalence ns shell, (B) Rydberg states correlat ed to dissociation limits involving an ion with a hole in its outervalence np shell plus an excited neutral atom. In dimers, class A states are "brigh t", that is, accessible by photoionization, and serve as an entrance step t o form the class B "dark" states; this character fades as the size of the c luster increases. In the dimer, the "Mulliken" E (2)Sigma(+) valence state is found to present a shallow potential well housing a few vibrational leve ls; it is predissociated by the class B Rydberg states. During the predisso ciation a remarkable energy transfer process is observed from the excited i on that loses its innershell electron to its neutral partner.