  The competition between intra molecular charge redistribution and
fragmentation has been studied in small molecules containing iodine by using
intense ultrashort pulses in the extreme ultraviolet regime (XUV). We show that
after an element specific inner-shell photoionization of diiodomethane
(CH$_2$I$_2$) and iodomethane (CH$_3$I), the induced positive charge is
redistributed with a significantly different efficiency. Therefore, we analyze
ion time-of-flight data obtained from XUV-pump XUV-probe experiments at the
Free Electron Laser in Hamburg (FLASH). Theoretical considerations on the basis
of ab initio electronic structure calculations including correlations relate
this effect to a strongly molecule specific, purely electronic charge
redistribution process that takes place directly after photoionization causing
a distribution of the induced positive charge predominantly on the atoms which
exhibit the lowest atomic ionization potential, i.e, in the molecules
considered, the iodine atom(s). As a result of the very different initial
charge distributions, the fragmentation timescales of the two molecules
experimentally observed are strikingly different.
