We have investigated the response of superhydrogenated gas-phase coronene cations upon soft x-ray absorption. Carbon (1s)⟶π^{⋆} transitions were resonantly excited at hν=285  eV. The resulting core hole is then filled in an Auger decay process, with the excess energy being released in the form of an Auger electron. Predominantly highly excited dications are thus formed, which cool down by hydrogen emission. In superhydrogenated systems, the additional H atoms act as a buffer, quenching loss of native H atoms and molecular fragmentation. Dissociation and transition state energies for several H loss channels were computed by means of density functional theory. Using these energies as input into an Arrhenius-type cascade model, very good agreement with the experimental data is found. The results have important implications for the survival of polyaromatic hydrocarbons in the interstellar medium and reflect key aspects of graphene hydrogenation.

Ion energy distributions arising from laser-produced plasmas of Sn are measured over a wide laser parameter space. Planar-solid and liquid-droplet targets are exposed to infrared laser pulses with energy densities between 1 J cm −2 and 4 kJ cm −2 and durations spanning 0.5 ps to 6 ns. The measured ion energy distributions are compared to two self-similar solutions of a hydrodynamic approach assuming isothermal expansion of the plasma plume into vacuum. For planar and droplet targets exposed to ps-long pulses, we find good agreement between the experimental results and the self-similar solution of a semi-infinite simple planar plasma configuration with an exponential density profile. The ion energy distributions resulting from solid Sn exposed to ns-pulses agrees with solutions of a limited-mass model that assumes a Gaussian-shaped initial density profile.

Ion distribution and ablation depth measurements of a fs-ps laser-irradiated solid tin target Deuzeman, M. J.; Stodolna, A. S.; Leerssen, E. E. B.; Antoncecchi, A.; Spook, N.; Kleijntjens, T.; Versluis, J.; Witte, S.; Eikema, K. S. E.; Ubachs, W. Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Deuzeman, M. J., Stodolna, A. S., Leerssen, E. E. B., Antoncecchi, A., Spook, N., Kleijntjens, T., ... Versolato, O. O. (2017). Ion distribution and ablation depth measurements of a fs-ps laser-irradiated solid tin target. Journal of Applied Physics, 121(10), [103301]. https://doi.org/10.1063/1.4977854 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Ion distribution and ablation depth measurements of a fs-ps laser-irradiated solid tin target The ablation of solid tin surfaces by a 800-nanometer-wavelength laser is studied for a pulse length range from 500 fs to 4.5 ps and a fluence range spanning from 0.9 to 22 J/cm 2 . The ablation depth and volume are obtained employing a high-numerical-aperture optical microscope, while the ion yield and energy distributions are obtained from a set of Faraday cups set up under various angles. We found a slight increase of the ion yield for an increasing pulse length, while the ablation depth is slightly decreasing. The ablation volume remained constant as a function of pulse length. The ablation depth follows a two-region logarithmic dependence on the fluence, in agreement with the available literature and theory. In the examined fluence range, the ion yield angular distribution is sharply peaked along the target normal at low fluences but rapidly broadens with increasing fluence. The total ionization fraction increases monotonically with fluence to a 5%-6% maximum, which is substantially lower than the typical ionization fractions obtained with nanosecond-pulse ablation. The angular distribution of the ions does not depend on the laser pulse length within the measurement uncertainty. These results are of particular interest for the possible utilization of fs-ps laser systems in plasma sources of extreme ultraviolet light for nanolithography. Published by AIP Publishing. [http://dx