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THU: Thursday Contributed Sessions

THU 4: Precise Quantum Molecules: Contributed Session to Symposium

THU 4.3: Talk

Thursday, September 11, 2025, 14:45–15:00, ZHG004

Observation of rovibrational state interference in molecule-surface collisions — •Christopher Reilly¹, Daniel J. Auerbach², and Rainer D. Beck¹ — ¹EPFL, Lausanne, Switzerland — ²MPINAT, Göttingen, Germany

While for all but the lightest molecular species the collisional generation and absorption of surface phonons typically obscures the ultimately quantum mechanical nature of molecule-surface collisions, a special continuous reflection symmetry in the interaction between methane and a gold surface permits observation of striking interference effects in the distribution of quantum states populated in the scattering event. Moreover, this interference effect is unique to molecules with some minimum amount of internal structure and is thus absent for the simpler molecular species typically studied.

Using laser-based quantum state preparation and detection, we are able to observe a novel form of high-contrast destructive interference between rovibrational states in molecule-surface scattering[1]. By exciting molecules to or from a rovibrational state of zero angular momentum, we prepare a state of pure reflection parity, and when probing the scattered molecules we find an almost total absence of population in states of the opposite parity. Reflection parity conservation is observed in both the ground and excited vibrational states, with constrast ratios approaching 100:1. High-contrast interference is also observed for rare vibrational relaxation events, shedding light on their microscopic mechanism.

[1] Reilly et al., Science 387, 962 (2025)

Keywords: Molecules; Interference; Lasers; Collisions; Surface science