Charge migration, charge transfer and charge-directed reactivity: from isolated to solvated molecules

Attosecond spectroscopy has opened a new window into electron dynamics, enabling direct observation of charge migration and charge transfer on their intrinsic time scales. Charge migration is a purely electronic dynamics driven by electronic coherence, which has been reconstructed and controlled using high-harmonic spectroscopy in iodoacetylene cation [1]. The development of attosecond soft-X-ray spectroscopy has considerably broadened the application range of attosecond spectroscopy. I will discuss the observation of the decoherence and revival of charge migration in neutral SiH₄, as well as coherence transfer between electronic states via conical intersections [2]. In CF₃I+, a 1.5-fs delay in charge transfer due to coupling through an intermediate state has been discovered, showing that population transfer between quantum states is not necessarily instantaneous [3]. Turning from electronic to non-adiabatic dynamics, the bifurcating Jahn–Teller dissociation of SiH₄⁺ into distinct ballistic and stochastic channels has been observed with 1-fs resolution [4] and a sub-7-fs electronic relaxation via a conical intersection in C₂H₄⁺ [5] have been observed. Advancing soft-X-ray spectroscopy to the liquid phase has revealed the charge-directed proton transfer in ionized urea dimers in aqueous solution [6]. A direct comparison of the UV-induced dynamics between isolated and solvated pyrazine molecules has revealed that electronic relaxation of isolated pyrazine molecules creates electronic dynamics between the two lowest-lying np* states, corresponding to a cyclic rearrangement of the electronic structure, which is fully suppressed in the aqueous solution in less than 40 fs [7]. These studies illustrate how attosecond techniques now resolve the ultrafast, purely electronic and non-adiabatic processes that govern photochemistry and molecular reactivity, offering new insights into the role of electron dynamics in chemical reactions and the influence of a solvation environment.

[1] Kraus et al., Science 350, 790 (2015)

[2] Matselyukh et al., Nat. Phys. 18, 1206 (2022)

[3] Matselyukh et al., Nat. Comm. 16, 7211 (2025)

[4] Matselyukh et al., Nat. Comm.16, 6540 (2025)

[5] Zinchenko et al., Science 371, 489 (2021)

[6] Yin et al., Nature 619, 749 (2023)

[7] Chang et al., Nat. Phys. 21, 137 (2025)