High Resolution Spectroscopy of NO in Helium Droplets: A Prototype for Open Shell Molecular Interactions in a Quantum Solvent. Klaus von Haeften A. Metzelthin S. Rudolph V. Staemmler M. Havenith 2381/542 https://figshare.le.ac.uk/articles/journal_contribution/High_Resolution_Spectroscopy_of_NO_in_Helium_Droplets_A_Prototype_for_Open_Shell_Molecular_Interactions_in_a_Quantum_Solvent_/10077329 We have measured the high-resolution infrared spectrum of the radical NO in the 2Π1/2 state in superfluid helium nanodroplets. The features are attributed to the Λ doubling splitting and the hyperfine structure. The hyperfine interaction is found to be unaffected by the He solvation. For the Λ-doubling splitting, we find a considerable increase by 55% compared to the gas phase. This is explained by a confinement of the electronically excited NO states by the surrounding He. The rotational level spacing is decreased to 76% of the gas phase value. The IR transition to the J = 1:5 state is found to be homogeneously broadened. We attribute both observations to the coupling between the molecular rotation and phonon/roton excitations in superfluid 4He droplets. 2007-08-02 10:14:22 IR content