# Electron spectroscopy for chemical analysis of liquids

## TL;DR

A new method called ESCAL is introduced for analyzing chemical structures in liquids with high accuracy, offering insights into molecular behavior that complements NMR.

## Contribution

The first internally consistent analysis of core-level chemical shifts in aqueous-phase solutes using ESCAL, enabling accurate and comparable measurements.

## Key findings

- C 1s spectra show functional-group-specific shifts that correlate with carbon oxidation state.
- Through-bond shifts are resolved, depending on specific functional-group interactions like carboxylic acid and ketone motifs.
- ESCAL provides element- and oxidation-state-specific structural data for liquid-phase analysis.

## Abstract

We present the first comprehensive, internally consistent analysis of core-level chemical shifts for aqueous-phase solutes using Electron Spectroscopy for Chemical Analysis of Liquids (ESCAL). An absolute binding-energy calibration enables high accuracy and cross-molecule comparability. The C 1s spectra of oxygenated aliphatic compounds display functional-group-specific shifts that increase with carbon oxidation state. Although these trends depart from gas- and solid-phase behavior, highlighting solvent and hydration effects, they correlate closely with calculated core-level orbital energies, providing a useful first-order predictor. We further resolve secondary, through-bond shifts over one and two bonds, the magnitudes of which depend sensitively on specific functional-group interactions (notably carboxylic acid and ketone motifs). Such element- and oxidation-state-specific structural information establishes the principles and reference data needed to build a predictive ESCAL database for liquid-phase structural and chemical analysis. The results will be contrasted with NMR studies.

Core-level chemical shifts of aqueous solutes measured by Electron Spectroscopy for Chemical Analysis of Liquids (ESCAL) show high sensitivity to molecular structure, enabling detailed resolution and making ESCAL complementary to established NMR.