1
|
Christ A, Härtl P, Seitz M, Edelmann T, Bode M, Waluk J, Leisegang M. Anisotropic coupling of individual vibrational modes to a Cu(110) substrate. Phys Chem Chem Phys 2023; 25:23894-23900. [PMID: 37642506 DOI: 10.1039/d3cp02911e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
We present a study on the excitation of individual vibrational modes with ballistic charge carriers propagating along the Cu(110) surface. By means of the molecular nanoprobe technique, where the reversible switching of a molecule-in this case tautomerization of porphycene-is utilized to detect excitation events, we reveal anisotropic coupling of two distinct vibrational modes to the substrate. The N-H bending mode, excited below |E| ≈ 376 meV, exhibits maxima perpendicular to the rows of the Cu(110) substrate and minima along the rows. In contrast, the N-H stretching mode, excited above |E| ≈ 376 meV, displays maxima along the rows and is constant otherwise. This inversion of the anisotropy reflects the orthogonality between the N-H bending and stretching mode. Additionally, we observe an energy-dependent asymmetry in the propagation direction of charge carriers injected into the Cu(110) surface state. Hereby, the anisotropic band structure results in a correlation between the group velocity and the tunneling probability into electronic states of the substrate.
Collapse
Affiliation(s)
- Andreas Christ
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
| | - Patrick Härtl
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
| | - Manuel Seitz
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
| | - Tobias Edelmann
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
| | - Matthias Bode
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
- Wilhelm Conrad Röntgen-Center for Complex Material Systems (RCCM), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Jacek Waluk
- Institut of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw, Poland
| | - Markus Leisegang
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
| |
Collapse
|
2
|
Czap G, Han Z, Wagner PJ, Ho W. Detection and Characterization of Anharmonic Overtone Vibrations of Single Molecules on a Metal Surface. PHYSICAL REVIEW LETTERS 2019; 122:106801. [PMID: 30932655 DOI: 10.1103/physrevlett.122.106801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Indexed: 06/09/2023]
Abstract
Inelastic electron tunneling spectroscopy (IETS) with the scanning tunneling microscope (STM) is a powerful technique used to characterize the vibration and spin states at the single-molecule level. While IETS lacks hard selection rules, historically it has been assumed that vibrational overtones are rarely seen or even absent. Here we provide definitive experimental evidence that the hindered rotation overtone excitation of carbon monoxide molecules adsorbed on Ag(110) can be detected with STM-IETS via isotope substitution. We also demonstrate that the anharmonicity of the overtone excitation can be characterized and compared between adsorption sites and find evidence of anisotropy in the vibrational anharmonicity for CO adsorbed on the [11[over ¯]0] step edge.
Collapse
Affiliation(s)
- Gregory Czap
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Zhumin Han
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Peter J Wagner
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - W Ho
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA
| |
Collapse
|