Freiburg 2024 – scientific programme

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MO: Fachverband Molekülphysik

MO 25: Novel Experimental Approaches

MO 25.4: Talk

Friday, March 15, 2024, 11:45–12:00, HS 3044

Charge density model for the interaction of molecules with vortex beams — Mikhail Maslov¹, Georgios M. Koutentakis¹, •Mateja Hrast¹, Oliver H. Heckl², and Mikhail Lemeshko¹ — ¹Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria — ²Christian Doppler Laboratory for Mid-IR Spectroscopy and Semiconductor Optics, Faculty Center for Nano Structure Research, Faculty of Physics, University of Vienna, Austria

We present a new model for the interaction of molecules with the orbital angular momentum of light, which has long been argued to benefit structural studies and quantum control of molecular ensembles. We derive a general description of the light-matter interaction in terms of the coupling between spherical gradients of the electric field and an effective molecular charge density that exactly reproduces molecular multipole moments. Our model can accommodate for an arbitrary complexity of the molecular structure and is applicable to any electric field, with the exception of tightly focused beams. Within this framework, we derive the general mechanism of angular momentum exchange between the spin and orbital angular momenta of light, molecular rotation and its center-of-mass motion. We demonstrate that vortex beams strongly enhance certain ro-vibrational transitions that are considered forbidden in the case of a non-helical light.

Keywords: Orbital angular momentum of light; Charge density model; Vortex beams; Ro-vibrational transitions