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

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.Comment: 12 pages, 7 figures, 5 table

Photoionization of Acetylene Doped in Helium Nanodroplets by EUV Synchrotron Radiation

Photoionization process of acetylene doped in helium nanodroplets is studied with EUV synchrotron radiation with photon energies between 20 and 26 eV by Photoelectron-Photoion Coincidence (PEPICO) experiment by detecting photoelectrons in coincidence with the photoions using electron velocity map imaging (VMI) spectrometer and ion time of flight (TOF) spectrometer. Acetylene is ionized in the droplet via Penning ionization at 21.6 eV photon energy. For photon energy of 23.9 eV and above the photoionization threshold of He, charge transfer ionization occurs in acetylene following autoionization and direct ionization in the droplet respectively

Intriguing Single Photon Induced Processes in Helium Nanodroplets

Helium nanodroplets are a unique system of quantum fluid clusters possessing several intriguing properties. From the perspective of atomic systems, they have been predominantly viewed as a spectroscopic matrix hosting other molecules and systems of interest. In this report, we draw particular attention to select electronic processes in He aggregates hosting other atoms, in particular, Rb. From this perspective, we present the details of single- and multi-electron processes occurring in this alkali-He system interacting with single extreme ultraviolet and soft X-ray photons. The features brought out in this study are generic and pertinent to systems with similar design on the atomic scale