Rostock 2019 – scientific programme

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MO: Fachverband Molekülphysik

MO 23: Molecular Theory

MO 23.3: Talk

Friday, March 15, 2019, 11:15–11:30, S HS 001 Biologie

An angulon quasiparticle perspective on impulsive molecular alignment in He nanodroplets. — •Igor Cherepanov, Giacomo Bighin, and Mikhail Lemeshko — IST Austria (Institute of Science and Technology Austria), Am Campus 1, Klosterneuburg, Austria

A quasiparticle picture provides a more straightforward and intuitive understanding of collective many-body phenomena arising in a variety of physical and chemical systems. Moreover, the problems which seem unsolvable within the classical approaches quite often become tractable from the quasiparticle perspective. This is the case for the microscopic dynamics of a single impurity immersed into a superfluid He droplet. Recently, the first experiments [1] showed that a short laser pulse can induce alignment of molecules dissolved in a He droplet. The rotational wavepacket dynamics herewith cannot be understood in terms of interference of the rigid rotor states due to the strong interactions with surrounding helium. Here we develop a dynamical theory of angulons [2] -- quasiparticles consisting of a rotating impurity dressed by a field of surrounding bath excitations (phonons). We demonstrate that the superfluid helium environment strictly limits the number of molecular states which can survive for a long time. Our theoretical framework allows to compute the change of the angular momentum belonging to the molecule and the helium bath in time. It opens up a possibility to have a look at the molecular alignment experiments from the point of view of redistribution of angular momentum. [1] D. Pantlehner et al., Phys. Rev. Lett. 110, 093002 (2013) [2] R. Schmidt, M. Lemeshko, Phys. Rev. Lett. 114, 203001 (2015)