A molecular conveyor belt by controlled delivery of single molecules into ultrashort laser pulses

Trapping and laser cooling in atomic physics enables control of single particles and their dynamics at the quantum level in a background-free environment. Ultrashort intense laser pulses reveal the ultimate control of electromagnetic fields, enabling the imaging of matter, in principle down to a single molecule or virus resolved on atomic scales. However, current methods fall short in overlapping each target with a pulse of comparable size. We combine the two fields by demonstrating a deterministic molecular conveyor, formed of electric trapping potentials. We deliver individual diatomic ions at millikelvin temperatures and with submicrometre positioning into few-femtosecond ultraviolet laser pulses. We initiate and probe the molecule's femtosecond dynamics and detect it and its response with 100% efficiency. This experiment might become key for investigations of individual molecules, such as structural determinations using few-femtosecond X-ray lasers. Our scheme may overlap each single molecule with a pulse, focused to (sub)micrometre size, providing the required number of photons at the repetition rate of the laser.