Theoretical and computational methods for tip- and surface-enhanced Raman scattering

Area of Science:

• Spectroscopy
• Plasmonics
• Computational Physics

Background:

• Raman spectroscopy provides molecular structure information.
• Surface-enhanced Raman scattering (SERS) and tip-enhanced Raman spectroscopy (TERS) utilize plasmonic fields to enhance sensitivity and resolution.
• Conventional Raman theory, using plane wave approximations, is challenged by the spatial confinement of plasmonic fields.

Purpose of the Study:

• To present a generalized theory for SERS and TERS within the effective field Hamiltonian (EFH) framework.
• To account for localized plasmonic field characteristics.
• To bridge theoretical modeling with experimental observations.

Main Methods:

• Development and application of the effective field Hamiltonian (EFH) theory.
• First-principles level quantitative simulations.
• Modeling of localized plasmonic fields.

Main Results:

• EFH successfully models localized plasmonic fields, enabling accurate simulations of SERS and TERS.
• The theory reveals underlying physics in experimental measurements.
• EFH predicts novel phenomena arising from plasmonic field properties (spatial, momentum, time, energy).

Conclusions:

• The EFH framework offers a robust theoretical foundation for SERS and TERS.
• First-principles simulations using EFH achieve quantitative agreement with experiments.
• The study introduces a computational package for SERS/TERS modeling and outlines future research directions.