Abstract
Attosecond probing of core-level electronic transitions provides a sensitive tool for studying valence molecular dynamics with atomic, state, and charge specificity. In this report, we employ attosecond transient absorption spectroscopy to follow the valence dynamics of strong-field initiated processes in methyl bromide. By probing the 3d core-to-valence transition, we resolve the strong field excitation and ensuing fragmentation of the neutral σ* excited states of methyl bromide. The results provide a clear signature of the non-adiabatic passage of the excited state wavepacket through a conical intersection. We additionally observe competing, strong field initiated processes arising in both the ground state and ionized molecule corresponding to vibrational and spin-orbit motion, respectively. The demonstrated ability to resolve simultaneous dynamics with few-femtosecond resolution presents a clear path forward in the implementation of attosecond XUV spectroscopy as a general tool for probing competing and complex molecular phenomena with unmatched temporal resolution.
Highlights
Attosecond probing of core-level electronic transitions provides a sensitive tool for studying valence molecular dynamics with atomic, state, and charge specificity
Femtosecond spectroscopy has been applied to study the regime where the nuclear dynamics become coupled with the electronic degrees of freedom within a molecule, leading to non-adiabatic transitions between different electronic states mediated by multi-dimensional conical intersections[5,6,7,8,9]
Due to the exquisite time resolution provided by attosecond transient absorption spectroscopy (ATAS), the results provide a signature of a non-adiabatic passage through a conical intersection, verified by molecular wavepacket propagation simulations
Summary
Attosecond probing of core-level electronic transitions provides a sensitive tool for studying valence molecular dynamics with atomic, state, and charge specificity. The demonstrated ability to resolve simultaneous dynamics with few-femtosecond resolution presents a clear path forward in the implementation of attosecond XUV spectroscopy as a general tool for probing competing and complex molecular phenomena with unmatched temporal resolution. This complexity cannot always be captured with coarse femtosecond time resolution. Numerous previous studies have investigated the velocity distributions of photofragments generated upon ultraviolet excitation and dissociation from the σ* excited A-band of CH3Br20–22 These energy-resolved studies have found that a conical intersection between the 3Q0þ a non-adiabatic transition probability and 1Q1 states gives rise to of ~15–30% from the 3Q0þ
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