Time-resolved imaging of laser-induced vibrational wave packets in neutral and ionic states of iodomethane
ORAL
Abstract
Light-driven vibrational wave packets play an important role in molecular imaging and coherent control applications. Here we present the results of a pump-probe experiment characterizing laser-induced vibrational wave packets in both, neutral and ionic states of CH$_{3}$I (iodomethane), one of the prototypical polyatomic systems. Measuring yields and kinetic energies of all ionic fragments as a function of the time delay between two 25 fs, 800 nm pump and probe pulses, we map vibrational motion of the molecule, and identify the states involved by channel-resolved Fourier spectroscopy. In the Coulomb explosion channels we observe features with \textasciitilde 130 fs periodicity resulting from C-I symmetric stretch ($\nu_{3}$ mode) of the electronically excited cationic state. However the Fourier transform of the low-energy I$^{+}$ ion yield produced by the dissociative ionization of CH$_{3}$I reveals the signatures of the same vibrational mode in the ground electronic states of both, neutral and cation, reflected in 65-70 fs oscillations. We observe the degeneration of the oscillatory structures from the cationic states within \textasciitilde 2 ps and discuss most likely reasons for this behavior.
*Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. DOE. K. R. P. and W. L. P. supported by NSF Award No. IIA-143049.
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