Rotational Excitation Spectroscopy with the STM through Molecular Resonances

Fabian Donat Natterer; François Patthey; Harald Brune

doi:10.1021/nn501999k

paper

Rotational Excitation Spectroscopy with the STM through Molecular Resonances

arXiv:1403.1312 · doi:10.1021/nn501999k

Abstract

We investigate the rotational properties of molecular hydrogen and its isotopes physisorbed on the surfaces of graphene and hexagonal boron nitride ( $h$ -BN), grown on Ni(111), Ru(0001), and Rh(111), using rotational excitation spectroscopy (RES) with the scanning tunneling microscope. The rotational thresholds are in good agreement with $Δ J = 2$ transitions of freely spinning para-H $_{2}$ and ortho-D $_{2}$ molecules. The line shape variations in RES for H $_{2}$ among the different surfaces can be traced back and naturally explained by a resonance mediated tunneling mechanism. RES data for H $_{2}$ / $h$ -BN/Rh(111) suggests a local intrinsic gating on this surface due to lateral variations in the surface potential. An RES inspection of H $_{2}$ , HD, and D $_{2}$ mixtures finally points to a multi molecule excitation, since either of the three $J = 0 \to 2$ rotational transitions are simultaneously present, irrespective of where the spectra were recorded in the mixed monolayer.

Rotational Excitation Spectroscopy with the STM through Molecular Resonances

Abstract

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