Oscillatory features are observed and attributed to a vibrational wave packet prepared in the A 2A1 state. The CH+3 and I+ pump-probe transients reflect the role of the IR pulse in controlling the photodynamics of CH3I+ in the A 2A1 state, mainly through the coupling to the ground state X 2E3/2,1/2 and to the excited B 2E state manifold.
#Iodine charge full#
The experimental results are complemented with high level ab initio calculations for the potential energy curves of the electronic states of CH3I+ as well as with full dimension on-the-fly trajectory calculations on the first electronically excited state A 2A1, considering the presence of the IR pulse. Photoelectrons and photofragment ions – CH+3 and I+ – are detected by velocity map imaging. A time-delayed IR probe pulse is used to probe the dissociative dynamics on the first excited A 2A1 state potential energy surface. A time-delay-compensated XUV monochromator is employed to isolate a specific harmonic, the 9th harmonic of the fundamental 800 nm (13.95 eV, 88.89 nm), which is used as a pump pulse to prepare the cation in several electronic states. The time-resolved photodynamics of the methyl iodide cation (CH3I+) are investigated by means of femtosecond XUV-IR pump-probe spectroscopy. We attribute this effect to a decreased charge transfer efficiency at larger internuclear separations, which are reached during longer pulses. While the overall degree of ionization is mainly defined by the pulse energy, our measurement reveals that the yield of the fragments with the highest charge states is enhanced for short pulse durations, in contrast to earlier observations for atoms and small molecules in the soft x-ray domain. We show that the timing of multiple ionization steps leading to a particular reaction product and, thus, the product’s final kinetic energy, is determined by the pulse duration rather than the pulse energy or intensity. Here, we report on a combined experimental and theoretical study of the ionization and fragmentation of iodomethane (CH3I) by ultraintense (∼1019 W/cm2) x-ray pulses at 8.3 keV, demonstrating how these dynamics depend on the x-ray pulse energy and duration. 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.
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