Coincident angle-resolved state-selective photoelectron spectroscopy of acetylene molecules: a candidate system for time-resolved dynamics

TL;DR

This study uses advanced photoelectron spectroscopy to explore ultrafast electronic and nuclear dynamics in acetylene molecules, revealing new insights into dissociation pathways and excited states relevant for time-resolved molecular physics.

Contribution

It provides a detailed analysis of acetylene's excited states and dissociation channels using coincidence spectroscopy in the EUV range, advancing understanding of molecular dynamics.

Findings

Identification of dissociation and isomerization channels

Revealed roles of excited states of C2H2+

Demonstrated effective probing of weak channels

Abstract

The acetylene-vinylidene system serves as a benchmark for investigations of ultrafast dynamical processes where the coupling of the electronic and nuclear degrees of freedom provides a fertile playground to explore the femto- and sub-femto-second physics with coherent extreme-ultraviolet (EUV) photon sources both on the table-top as well as free-electron lasers. We focus on detailed investigations of this molecular system in the photon energy range $19...40$ eV where EUV pulses can probe the dynamics effectively. We employ photoelectron-photoion coincidence (PEPICO) spectroscopy to uncover hitherto unrevealed aspects of this system. In this work, the role of excited states of the $C_{2}H_{2}^{+}$ cation, the primary photoion, is specifically addressed. From photoelectron energy spectra and angular distributions, the nature of the dissociation and isomerization channels is discerned. Exploiting the $4\pi$-collection geometry of velocity map imaging spectrometer, we not only probe pathways where the efficiency of photoionization is inherently high but also perform PEPICO spectroscopy on relatively weak channels.