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Updated: May 29, 2026
10:52
Direct Imaging of Laser-driven Ultrafast Molecular Rotation
Published on: February 4, 2017
Vibrational excitations in molecular layers probed by ballistic electron microscopy
Rasanayagam Sivasayan Kajen1, Natarajan Chandrasekhar, Xinliang Feng
1Institute of Materials Research and Engineering, 3 Research Link, 117602, Singapore.
Nanotechnology
|September 30, 2011
Summary
We reveal molecular vibrational modes using ballistic electron emission spectroscopy (BEES). This new method identifies vibronic excitations in polycyclic aromatic hydrocarbon (PAH) layers without high fields or device bias.
Area of Science:
- Surface Science
- Molecular Spectroscopy
- Condensed Matter Physics
Background:
- Derivative spectroscopy often requires high fields, potentially altering molecular properties.
- Understanding molecular vibrations is crucial for material characterization.
Purpose of the Study:
- To demonstrate a novel method for characterizing molecular vibrational modes.
- To investigate vibronic excitations in polycyclic aromatic hydrocarbon (PAH) layers using ballistic electron emission spectroscopy (BEES).
Main Methods:
- Utilizing the second derivative (d(2)I(B)/dV(2)) of the BEES current to probe vibrational information.
- Performing BEES on three types of large PAH molecular layers under zero bias conditions.
Main Results:
- The d(2)I(B)/dV(2) spectra revealed uniformly spaced peaks, indicative of vibronic excitations.
- Peak spacing was consistent within the same PAH family, despite variations in onset voltage.
- Specific vibrational modes correlated with orbital injection, suggesting symmetry principles at play.
Conclusions:
- The second derivative of BEES current is an effective tool for studying molecular vibrations.
- This method offers a field-free alternative to conventional derivative spectroscopy.
- BEES provides insights into the relationship between electronic structure and vibrational modes in PAH molecules.
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