Rabi oscillations in a stretching molecule

Rabi oscillation is an elementary laser-driven physical process in atoms and artificial atoms from solid-state systems,while it is rarely demonstrated in molecules.Here,we investigate the bond-length-dependent Rabi oscillations with varying Rabi frequencies in strong-laser-field dissociation of H2+.The coupling of the bond stretching and Rabi oscillations makes the nuclei gain different kinetic energies while the electron is alternatively absorbing and emitting photons.The resulting proton kinetic energy spectra show rich structures beyond the prediction of the Floquet theorem and the well-accepted resonant one-photon dissociation pathway.Our study shows that the laser-driven Rabi oscillations accompanied by nuclear motions are essential to understanding the bond-breaking mechanism and provide a time-resolved perspective to manipulate rich dynamics of the strong-laser-field dissociation of molecules.

Low-Energy Protons in Strong-Field Dissociation of H_(2)^(+) via Dipole-Transitions at Large Bond Lengths

More than ten years ago,the observation of the low-energy structure in the photoelectron energy spectrum,regarded as an“ionization surprise,”has overthrown our understanding of strong-field physics.However,the similar low-energy nuclear fragment generation from dissociating molecules upon the photon energy absorption,one of the well-observed phenomena in light-molecule interaction,still lacks an unambiguous mechanism and remains mysterious.Here,we introduce a time-energy-resolved manner using a multicycle near-infrared femtosecond laser pulse to identify the physical origin of the light-induced ultrafast dynamics of molecules.By simultaneously measuring the bond-stretching times and photon numbers involved in the dissociation of H_(2)^(+) driven by a polarization-skewed laser pulse,we reveal that the low-energy protons(below 0.7 eV)are produced via dipole-transitions at large bond lengths.The observed low-energy protons originate from strong-field dissociation of high vibrational states rather than the low ones of H_(2)^(+) cation,which is distinct from the well-accepted bond-softening picture.Further numerical simulation of the time-dependent Schrödinger equation unveils that the electronic states are periodically distorted by the strong laser field,and the energy gap between the field-dressed transient electronic states may favor the one-or three-photon transitions at the internuclear distance larger than 5 a.u.The time-dependent scenario and our time-energy-resolved approach presented here can be extended to other molecules to understand the complex ultrafast dynamics.