Second-Order Spectral Lineshapes from Charged Interfaces

TL;DR

This paper models how interfacial potentials affect second-order spectral lineshapes in nonlinear spectroscopy, emphasizing the importance of accounting for potential-dependent terms to accurately interpret charged interface spectra.

Contribution

It introduces a mathematical model to analyze the influence of interfacial potentials on second-order spectral lineshapes, highlighting the need to consider potential-dependent contributions for correct spectral interpretation.

Findings

Interfacial potentials significantly alter spectral lineshapes.

Accounting for (3) term improves spectral interpretation.

Model aligns with experimental spectra from charged interfaces.

Abstract

Second-order nonlinear spectroscopy has proven to be a powerful tool in elucidating key chemical and structural characteristics at a variety of interfaces. However, the presence of interfacial potentials may lead to complications regarding the interpretation of second harmonic and vibrational sum frequency generation responses from charged interfaces due to mixing of absorptive and dispersive contributions. Here, we examine by means of mathematical modeling how this interaction influences second-order spectral lineshapes. We discuss our findings in the context of reported nonlinear optical spectra obtained from charged water/air and solid/liquid interfaces and demonstrate the importance of accounting for the interfacial potential-dependent \c{hi}(3) term in interpreting lineshapes when seeking molecular information from charged interfaces using second-order spectroscopy.