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3 results on '"Kukk, E. (E.)"'

1. Formative period in the x-ray-induced photodissociation of organic molecules

Author

Kukk, E. (E.), Fukuzawa, H. (H.), Niskanen, J. (J.), Nagaya, K. (K.), Kooser, K. (K.), You, D. (D.), Peschel, J. (J.), Maclot, S. (S.), Niozu, A. (A.), Saito, S. (S.), Luo, Y. (Y.), Pelimanni, E. (E.), Itälä, E. (E.), Bozek, J. D. (J. D.), Takanashi, T. (T.), Berholts, M. (M.), Johnsson, P. (P.), and Ueda, K. (K.)

Abstract

Absorption of x-ray photons by atomic inner shells of light-element organics and biomolecules often leads to formation of dicationic electronic states and to molecular fragmentation. We investigated the x-ray-induced dissociation landscape of a representative medium-sized organic molecule, thiophene, by femtosecond x-ray pulses from the Super Photon Ring-8 GeV (SPring-8) Angstrom Compact Free-Electron Laser (SACLA). Holes, created in the sulfur 2p orbital by photoemission, were filled by the Auger process that created dicationic molecular states within a broad range of internal energies—a starting point particular to x-ray-induced dynamics. The evolution of the ionized molecules was monitored by a pump-probe experiment using a near-infrared (800 nm) laser pulse. Ion-ion coincidence and ion momentum analysis reveals enhanced yields of ionic fragments from multibody breakup of the ring, attributed to additional ionization of the highly excited fraction of the dicationic parent molecular states. The transient nature of the enhancement and its decay with about a 160-fs time constant indicate formation of an open-ring parent geometry and the statistical survival time of the parent species before the dissociation events. By probing specific Auger final states of transient, highly excited nature by near-infrared light, we demonstrate how pump-probe signatures can be related to the key features in dynamics during the early period of the x-ray-induced damage of organic molecules and biomolecules.

Published
2021

2. Coulomb implosion of tetrabromothiophene observed under multiphoton ionization by free-electron-laser soft-x-ray pulses

Author

Kukk, E. (E.), Myllynen, H. (H.), Nagaya, K. (K.), Wada, S. (S.), Bozek, J. D. (J. D.), Takanashi, T. (T.), You, D. (D.), Niozu, A. (A.), Kooser, K. (K.), Gaumnitz, T. (T.), Pelimanni, E. (E.), Berholts, M. (M.), Granroth, S. (S.), Yokono, N. (N.), Fukuzawa, H. (H.), Miron, C. (C.), Ueda, K. (K.), Kukk, E. (E.), Myllynen, H. (H.), Nagaya, K. (K.), Wada, S. (S.), Bozek, J. D. (J. D.), Takanashi, T. (T.), You, D. (D.), Niozu, A. (A.), Kooser, K. (K.), Gaumnitz, T. (T.), Pelimanni, E. (E.), Berholts, M. (M.), Granroth, S. (S.), Yokono, N. (N.), Fukuzawa, H. (H.), Miron, C. (C.), and Ueda, K. (K.)

Abstract

Soft-x-ray free-electron-laser pulses were used to create highly charged molecular tetrabromothiophene species by sequential multiphoton ionization from bromine 3d orbitals. The experiment was performed at the SACLA facility in Japan and the products of molecular dissociation were analyzed by means of multicoincidence momentum-resolved ion time-of-flight spectroscopy. Total charge states up to +13 atomic units were produced, creating a particular dissociation pattern for the carbon ions, a Coulomb implosion, due to the concerted forces by the surrounding heavy bromine ions. This behavior was explored both experimentally and by numerical molecular-dynamics simulations and the fingerprints of the Coulomb implosion were identified in both. In simulations, Coulomb implosion was predicted to be highly sensitive to the initial (thermal) motion of the atoms and, after including vibrational motion for several temperatures, good general agreement between the experiment and simulations was found. The agreement with the experiment was further improved by adding charge dynamics to the simulation, according to our point-charge dynamics model with empirical rate constants.

Published
2019

3. FinEstBeaMS:a wide-range Finnish-Estonian beamline for materials science at the 1.5 GeV storage ring at the MAX IV Laboratory

Author

Pärna, R. (R.), Sankari, R. (R.), Kukk, E. (E.), Nõmmiste, E. (E.), Valden, M. (M.), Lastusaari, M. (M.), Kooser, K. (K.), Kokko, K. (K.), Hirsimäki, M. (M.), Urpelainen, S. (S.), Turunen, P. (P.), Kivimäki, A. (A.), Pankratov, V. (V.), Reisberg, L. (L.), Hennies, F. (F.), Tarawneh, H. (H.), Nyholm, R. (R.), and Huttula, M. (M.)

Subjects
Beamlines, MAX IV, VUV
Abstract

The FinEstBeaMS beamline is under construction at the 1.5 GeV storage ring of the MAX IV Laboratory at Lund, Sweden. It has been designed to cover an unusually wide energy range from ultraviolet (4.3 eV) to soft X-rays (1000 eV) but experiments will also be possible at the Mg and Al Kα energies. Instead of having two different insertion devices and optical schemes for low and high photon energy regions, we have based our design on a single long-period, elliptically polarizing undulator and a plane grating monochromator. This solution will provide very good conditions for planned experiments in the whole photon energy region. The beamline will have two branches: one will mainly be used to investigate free atoms, molecules and clusters with photoelectron/photoion coincidence spectroscopy as well as solids with photoluminescence spectroscopy whereas the other one will be dedicated to ultra-high vacuum studies of surfaces and interfaces, utilizing X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. This paper focuses on the optical design of the beamline and general design concepts of the gas phase and solid state end stations.

Published
2017

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