SAMOP 2023 – wissenschaftliches Programm

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SYQR: Symposium Quantum Optics and Quantum Information with Rigid Rotors

SYQR 1: Quantum Optics and Quantum Information with Rigid Rotors 1

SYQR 1.1: Hauptvortrag

Freitag, 10. März 2023, 11:00–11:30, E415

Femtosecond timed imaging of rotation and vibration of alkali dimers on the surface of helium nanodroplets — •Henrik Stapelfeldt — Aarhus University, Aarhus, Denmark

Dimers of sodium or potassium, residing on the surface of helium nanodroplets, are set into rotation and vibration, through the dynamic Stark effect, by a moderately intense femtosecond pump pulse. Coulomb explosion of the dimers, induced by an intense, delayed femtosecond probe pulse, is used to record the time-dependent nuclear motion.

Concerning rotation, the measured alignment traces show a distinct, periodic structure that differs qualitatively from the well-known alignment dynamics of linear molecules in either the gas phase or dissolved in liquid helium. Instead, the observed alignment dynamics of Na2 and of K2 agree with that obtained from a 2D rigid rotor model, strongly indicating that the rotation of each dimer occurs in a plane, defined by the He droplet surface.

Concerning vibration, the Coulomb explosion probe method enables us to measure the distribution of internuclear distances as a function of time. For K2, we observe a distinct oscillatory pattern caused by a two-state vibrational wave packet in the initial electronic state of the dimer. The wave packet is imaged for more than 250 vibrational periods with a precision better than 0.1 Å on its central position and a resolution < 1 Å of its shape. Unlike the rotational motion, the vibration of the dimer is essentially unaffected by the presence of the He droplet.