Coherent radiation in the extreme ultraviolet (XUV) range obtained by high harmonic generation (HHG) brings Femtochemistry studies beyond their traditional realm. This XUV light source can be used as a short pump pulse which ionizes neutral molecules leaving the molecular cation in a combination of excited electronic states. The relaxation of the cation dynamics thus initiated can be probed using short conventional IR or visible laser pulses. Such schemes have proven successful for the study of the dynamics of homonuclear diatomic cations [1,2]. In this work we show the results of an XUV-IR experiment which demonstrates that these schemes can be extended to polyatomic molecules. In particular, the case of the iodometane cation (CH3I+) is explored in experiments involving ionization with monochromatized HHG light (9th or 11th harmonic of the 800 nm fundamental radiation, with 14.0 eV or 17.1 eV photon energy, respectively) followed by probe with a 25 fs 800 nm pulse. CH3+ and I+ fragments are detected in velocity-mapping configuration. Coherent vibrational dynamics is observed in the first excited electronic state of CH3I+. A 1D wave packet calculation of the system has been performed which provides crucial insight into the nature of the couplings to the electronic states responsible for the probing mechanism.

Femtosecond dynamics in the iodomethane cation investigated by XUV-IR pump-probe ion imaging

256th National Meeting (2018)

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