Imaging molecular potentials using ultrahigh-resolution resonant photoemission

  • A Corrigendum to this article was published on 01 December 2015

Abstract

Electron-density distributions and potential-energy surfaces are important for predicting the physical properties and chemical reactivity of molecular systems. Whereas angle-resolved photoelectron spectroscopy enables the reconstruction of molecular-orbital densities of condensed species1, absorption or traditional photoelectron spectroscopy are widely employed to study molecular potentials of isolated species. However, the information they provide is often limited because not all vibrational substates are excited near the vertical electronic transitions from the ground state. Moreover, many electronic states cannot be observed owing to selection rules or low transition probabilities. In many other cases, the extraction of the potentials is impossible owing to the high densities of overlapping electronic states. Here we use resonant photoemission spectroscopy, where the absence of strict dipole selection rules in Auger decay enables access to a larger number of final states as compared with radiative decay. Furthermore, by populating highly excited vibrational substates in the intermediate core-excited state, it is possible to ‘pull out’ molecular states that were hidden by overlapping spectral regions before.

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Figure 1: Ab initio potential-energy curves, direct photoemission (PE) and RPE spectra of N2.
Figure 2: RPE spectra of nitrogen molecule obtained for a series ν=0–6 of vibrational substates of the 1s−1π* core-excited state.
Figure 3: Controlling the extension of the vibrational wavefunctions in the intermediate core-excited state through the X-ray photon energy.
Figure 4: Comparison between the reconstructed molecular potentials based on ultrahigh-resolution RPE data and ab initio calculated potentials (circles).

Change history

  • 19 November 2015

    In the version of this Letter originally published the state with Emin = 23 eV was mislabelled throughout and should have been labelled 12ϕg. This has been corrected in the online versions 19 November 2015.

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Acknowledgements

Experiments were carried out at the PLEIADES beamline at SOLEIL Synchrotron, France (proposal number 99090106). We are grateful to J. B. A. Mitchell for his suggestions, to E. Robert for technical assistance and to the SOLEIL staff for smoothly running the facility. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement 252781, from Triangle de la physique under contract 2007-010T, from JSPS and from the Swedish Research Council.

Author information

C.M. suggested and planned the experiment. C.N., O.T. and C.M. collected the data, and V.K. and O.T. carried out the data analysis. Y.S., F.G., N.K. and V.K. carried out the theoretical analysis. C.M., F.G. and V.K. wrote the paper and O.T. contributed to figure production. All authors discussed the results and commented on the manuscript.

Correspondence to Catalin Miron.

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The authors declare no competing financial interests.

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Miron, C., Nicolas, C., Travnikova, O. et al. Imaging molecular potentials using ultrahigh-resolution resonant photoemission. Nature Phys 8, 135–138 (2012) doi:10.1038/nphys2159

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