Pulse Energy and Pulse Duration Effects in the Ionization and Fragmentation of Iodomethane by Ultraintense Hard X Rays

The interaction of intense femtosecond x-ray pulses with molecules sensitively depends on the interplay between multiple photoabsorptions, Auger decay, charge rearrangement, and nuclear motion. Here, we report a combined experimental theoretical study ionization fragmentation iodomethane (CH_{3}I) by ultraintense (?10^{19}??W/cm^{2}) at 8.3 keV, demonstrating how these dynamics depend pulse energy duration. We show that timing steps leading to particular reaction product and, thus, product's final kinetic energy, is determined duration rather than or intensity. While overall degree mainly defined our measurement reveals yield fragments highest states enhanced for short durations, in contrast earlier observations atoms small soft domain. attribute this effect decreased transfer efficiency larger internuclear separations, which are reached during longer pulses.