Ultrafast ring opening in CHD investigated by simplex-based spectral unmixing

TL;DR

This study employs spectral unmixing to analyze ultrafast ring opening in CHD, identifying transient photoproducts and their evolution with high temporal resolution using laser-induced fragmentation.

Contribution

It introduces a simplex-based spectral unmixing method to decompose transient spectra into distinct photoproducts during ultrafast ring opening in CHD.

Findings

At least three spectra are needed to model the transient data.

Decomposition reveals the appearance timing of CHD, CHD+, and HT.

The method tracks product evolution during ring opening.

Abstract

We use spectral unmixing to determine the number of transient photoproducts and to track their evolution following the photo- excitation of 1,3-cyclohexadiene (CHD) to form 1,3,5-hexatriene (HT) in the gas phase. The ring opening is initiated with a 266 nm ultraviolet laser pulse and probed via fragmentation with a delayed intense infrared 800 nm laser pulse. The ion time-of-flight (TOF) spectra are analyzed with a simplex-based spectral unmixing technique. We find that at least three independent spectra are needed to model the transient TOF spectra. Guided by mathematical and physical constraints, we decompose the transient TOF spectra into three spectra associated with the presence of CHD, CHD+, and HT, and show how these three products appear at different times during the ring opening.