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

Abstract

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 $\ifmmode\pm\else\textpm\fi{}$ 15) fs full-width-at-half-maximum. (ii) With the onset of the I${}_{2}$${}^{2+}$ fragmentation the probability to lose a further electron within the same optical laser pulse rises with increasing I${}^{+}$---I${}^{+}$ internuclear separation and reaches its maximum after $\ensuremath{\sim}$30 fs with respect to the pulse maximum. (iii) Charge separation into the I${}_{2}$${}^{2+}\ensuremath{\rightarrow}{\mathrm{I}}^{2+}+\mathrm{I}$ dissociative channel with an asymmetric charge distribution is completed after (121 $\ifmmode\pm\else\textpm\fi{}$ 22) fs.