Core level excitation of weakly bonded atomic and molecular species is reported. Excitations into unoccupied orbitals with valence and Rydberg character as well as into the corresponding K- and L-continua are compared with the isolated and condensed species. Core level excitation of clusters is also accompagned with extensive fragmentation of singly and doubly charged clusters. Coincidence techniques such as photoelectron-photoion-coincidences (PEPICO) and photoion-photoion-coincidence (PIPICO) are used to study the photochemical fragmentation pathways of core excited clusters. Kinetic energy releases related to charge separation of cluster dications (Coulomb explosion) are derived from PIPICO spectra. The fragmentation energetics is discussed in relation to cluster dication threshold energies.