An asymmetric fitting function for condensed-phase Raman spectroscopy.

Area of Science:

• Spectroscopy
• Condensed Matter Physics
• Materials Science

Background:

• Asymmetric lineshapes are common in Raman spectra of condensed matter.
• Traditional symmetric fitting functions (e.g., pseudo-Voigt) yield unreliable peak parameters for asymmetric data.
• A need exists for a practical asymmetric fitting function with simple form and accurate data description.

Purpose of the Study:

• To formulate a novel asymmetric pseudo-Voigt function.
• To ensure the function meets criteria for practical use: simple analytic form, minimal parameters, and accurate data representation.
• To address limitations of symmetric fitting functions in analyzing asymmetric Raman spectral data.

Main Methods:

• Developed an asymmetric pseudo-Voigt function by introducing a damped perturbation to symmetric shapes.
• Incorporated a single asymmetry-related parameter to control the line shape.
• Tested the function by fitting experimental Raman spectra from diverse condensed matter samples.

Main Results:

• The proposed asymmetric pseudo-Voigt function accurately describes experimental Raman spectra with asymmetric lineshapes.
• The function demonstrates consistent behavior of spectral line tails due to its damped perturbation approach.
• Successfully applied to various materials including crystals, nanoparticles, polymers, and molecular solids/liquids.

Conclusions:

• The new asymmetric pseudo-Voigt function offers a reliable and practical tool for analyzing Raman spectra with asymmetric features.
• It overcomes the limitations of symmetric fitting functions, providing accurate parameter estimation.
• The function's versatility makes it applicable across a broad range of condensed matter systems.