The disintegration mechanisms for xenon clusters in intense femtosecond soft x-ray pulses from the FLASH free electron laser are investigated. The clusters are irradiated at a wavelength of λ = 13.7 nm (hν = 90.5 eV) and power densities of 5 × 1014 W cm-2. During the 10 fs pulse the Xe clusters are transformed into a highly excited, multiply charged nanoplasma. Simulating the ion kinetic energies in an electrostatic model suggests that highly charged ions explode off the surface due to Coulomb repulsion while the inner core expands in a hydrodynamic expansion. The current results yield evidence for efficient ionization of the clusters in addition to direct multistep photoemission. © 2009 IOP Publishing Ltd.4213 Bostedt, C., Al, E., Experiments at FLASH (2009) Nucl. Instrum. Methods A, 601, p. 108Saalmann, U., Ch, S., Rost, J.M., Mechanisms of cluster ionization in strong laser pulses (2006) J. Phys. B: At. Mol. Opt. 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