Transient x-ray absorption spectroscopy of hydrated halogen atom

TL;DR

This study uses time-resolved x-ray absorption spectroscopy to observe hydrated bromine atoms generated in water, revealing their lifetime, reactivity, and solvent interactions through spectral analysis and simulations.

Contribution

It provides the first direct spectroscopic observation of hydrated bromine atoms and characterizes their transient behavior and solvent environment.

Findings

Hydrated bromine atoms have a lifetime of about 17 ns.

Nearly half of the bromine atoms react with bromide to form Br2-.

The solvent shell around Br0 is mainly hydrophobic, confirmed by Monte Carlo simulations.

Abstract

Time-resolved x-ray absorption spectroscopy monitors the transient species generated by one-photon detachment of an electron from aqueous bromide. Hydrated bromine atoms with a lifetime of ca. 17 ns were observed, nearly half of which react with excess Br- to form Br2-. The K-edge spectra of the Br atom and Br2- anion exhibit distinctive resonant transitions that are absent for the Br- precursor. The absorption spectra indicate that the solvent shell around a Br0 atom is defined primarily by hydrophobic interactions, in agreement with a Monte Carlo simulation of the solvent structure.