Quantum tunneling effect on the surface enhanced Raman process in molecular systems.

Area of Science:

• Physical Chemistry
• Nanoscience
• Spectroscopy

Background:

• Surface-enhanced Raman scattering (SERS) is a powerful technique for molecular detection.
• Sub-nanometer nanocavities in metallic dimers offer unique environments for SERS.
• Quantum effects become significant at these nanoscale dimensions.

Purpose of the Study:

• To theoretically investigate the influence of quantum tunneling on SERS.
• To analyze the role of sub-nanometer cavity size on SERS spectra.
• To understand the interplay between plasmonic enhancement and quantum effects.

Main Methods:

• Quantum corrected model for tunneling.
• Finite element simulations for nanocavity analysis.
• Density matrix method for SERS spectra calculation.

Main Results:

• SERS intensity is highly sensitive to nanocavity size.
• Quantum tunneling suppresses local field enhancement and SERS intensity in small gaps.
• Charge neutralization due to tunneling is identified as the suppression mechanism.

Conclusions:

• Quantum tunneling is a critical factor in SERS within sub-nanometer nanocavities.
• Both plasmonic field enhancement and molecular decay rates must be considered.
• Findings aid in understanding molecular systems in nanoscale plasmonic structures.