Strong-field ionization of molecular iodine traced with XUV pulses from a free-electron laser

Ultrafast dynamics of a molecular wave packet created by a strong 120-fs near-infrared (800 nm) laser pulse in iodine has been probed by synchronized 13.4-nm, 35-fs extreme-ultraviolet pulses delivered by the free-electron laser facility in Hamburg, FLASH. The kinetic energy release of the multiply charged ionic fragments reveals three essential steps of strong-field-induced molecular fragmentation dynamics: (i) The creation of I-2(2+) and (I-2(2+))* molecular ions proceeds within (75 +/- 15) fs full-width-at-half-maximum. (ii) With the onset of the I-2(2+) fragmentation the probability to lose a further electron within the same optical laser pulse rises with increasing I+-I+ internuclear separation and reaches its maximum after similar to 30 fs with respect to the pulse maximum. (iii) Charge separation into the I-2(2+) -> I-2(+) + I dissociative channel with an asymmetric charge distribution is completed after (121 +/- 22) fs.