Subfemtosecond Tracing of Molecular Dynamics during Strong-Field Interaction

This is the authors' abstract. We don't add key points for this paper.

We introduce and experimentally demonstrate a method where the two intrinsic timescales of a molecule, the slow nuclear motion and the fast electronic motion, are simultaneously measured in a photoelectron photoion coincidence experiment. In our experiment, elliptically polarized, 750 nm, 4.5 fs laser pulses were focused to an intensity of 9×10¹⁴ W/cm² onto H₂. Using coincidence imaging, we directly observe the nuclear wave packet evolving on the 1sσg state of H₂⁺ during its first round-trip with attosecond temporal and picometer spatial resolution. The demonstrated method should enable insight into the first few femtoseconds of the vibronic dynamics of ionization-induced unimolecular reactions of larger molecules.