Profiles

Henning Zettergren

Henning Zettergren

Universitetslektor

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Arbetar vid Fysikum
Telefon 08-553 786 34
E-post henning@fysik.su.se
Besöksadress Roslagstullsbacken 21 C, plan 4, Albano
Rum C4:3027
Postadress AlbaNova universitetscentrum, Fysikum 106 91 Stockholm

Publikationer

I urval från Stockholms universitets publikationsdatabas
  • 2017. Henning Zettergren. Nuclear Instruments and Methods in Physics Research Section B 408, 9-15

    This brief review highlights recent advances in our understanding on how fullerenes, Polycyclic Aromatic Hydrocarbons (PAHs), and their clusters respond to singly and multiply charged keV-ion impact. These studies reveal how the projectile charge, mass, and velocity may be tuned to investigate, e.g., the stabilities of multiply charged monomers and clusters, different monomer and cluster cooling processes, molecular heating by Coulomb explosions of highly charged clusters, and impulse driven molecular growth processes.

  • 2017. Marcelo Goulart (et al.). Physical Chemistry, Chemical Physics - PCCP 19 (41), 27968-27973

    Mass spectra of helium nanodroplets doped with H-2 and coronene feature anomalies in the ion abundance that reveal anomalies in the energetics of adsorption sites. The coronene monomer ion strongly adsorbs up to n = 38 H-2 molecules indicating a commensurate solvation shell that preserves the D-6h symmetry of the substrate. No such feature is seen in the abundance of the coronene dimer through tetramer complexed with H-2; this observation rules out a vertical columnar structure. Instead we see evidence for a columnar structure in which adjacent coronenes are displaced in parallel, forming terraces that offer additional strong adsorption sites. The experimental value for the number of adsorption sites per terrace, approximately six, barely depends on the number of coronene molecules. The displacement estimated from this number exceeds the value reported in several theoretical studies of the bare, neutral coronene dimer.

  • 2017. Linda Giacomozzi (et al.). Physical Chemistry, Chemical Physics - PCCP 19 (30), 19750-19755

    We have studied collisions between tetraphenylporphyrin cations and He or Ne at center-of-mass energies in the range 50-110 eV. The experimental results were interpreted in view of density functional theory calculations of dissociation energies and classical molecular dynamics simulations of how the molecules respond to the He/Ne impact. We demonstrate that prompt atom knockout strongly contributes to the total destruction cross sections. Such impulse driven processes typically yield highly reactive fragments and are expected to be important for collisions with any molecular system in this collision energy range, but have earlier been very difficult to isolate for biomolecules.

  • 2017. Henning T. Schmidt (et al.). Physical Review Letters 119 (7)

    We apply near-threshold laser photodetachment to characterize the rotational quantum level distribution of OH- ions stored in the cryogenic ion-beam storage ring DESIREE at Stockholm University. We find that the stored ions relax to a rotational temperature of 13.4 +/- 0.2 K with 94.9 +/- 0.3% of the ions in the rotational ground state. This is consistent with the storage ring temperature of 13.5 +/- 0.5 K as measured with eight silicon diodes but in contrast to all earlier studies in cryogenic traps and rings where the rotational temperatures were always much higher than those of the storage devices at their lowest temperatures. Furthermore, we actively modify the rotational distribution through selective photodetachment to produce an OH- beam where 99.1 +/- 0.1% of approximately one million stored ions are in the J = 0 rotational ground state. We measure the intrinsic lifetime of the J = 1 rotational level to be 145 +/- 28 s.

  • 2016. Michael Gatchell, Henning Zettergren. Journal of Physics B 49 (16)

    Energetic ions lose some of their kinetic energy when interacting with electrons or nuclei in matter. Here, we discuss combined experimental and theoretical studies on such impulse driven reactions in polycyclic aromatic hydrocarbons (PAHs), fullerenes, and pure or mixed clusters of these molecules. These studies show that the nature of excitation is important for how complex molecular systems respond to ion/atom impact. Rutherford-like nuclear scattering processes may lead to prompt atom knockout and formation of highly reactive fragments, while heating of the molecular electron clouds in general lead to formation of more stable and less reactive fragments. In this topical review, we focus on recent studies of knockout driven reactions, and present new calculations of the angular dependent threshold (displacement) energies for such processes in PAHs. The so-formed fragments may efficiently form covalent bonds with neighboring molecules in clusters. These unique molecular growth processes may be important in astrophysical environments such as low velocity shock waves.

  • 2016. S. E. Huber (et al.). Carbon 109, 843-850

    Fullerenes (and clusters composed of them) yield a variety of promising structural, electronic, magnetic and chemical properties, governed by their specific electronic and geometric configuration. These systems have attracted many theoretical and experimental endeavors in order to describe, explain and predict their features. The conclusive description of some specific properties has remained a challenge though, such as a sound physicochemical description of the stability of multiply charged fullerene clusters, which we explore here. We show how simple models based on classical electrostatics allow one to understand the (fragmentation) dynamics of multiply ionized fullerene aggregates without the use of elaborate and time-consuming computational quantum chemical approaches. These models successfully explain why the fullerene pentamer is the smallest dicationic cluster experimentally observed, despite its thermodynamic instability. These predictions are of importance in various fields such as cluster physics, astrochemistry, electrochemistry and solid-state chemistry.

  • 2016. Fredrik Lindén, Henrik Cederquist, Henning Zettergren. Journal of Chemical Physics 145 (19)

    We present exact analytical solutions for charge transfer reactions between two arbitrarily charged hard dielectric spheres. These solutions, and the corresponding exact ones for sphere-sphere interaction energies, include sums that describe polarization effects to infinite orders in the inverse of the distance between the sphere centers. In addition, we show that these exact solutions may be approximated by much simpler analytical expressions that are useful for many practical applications. This is exemplified through calculations of Langevin type cross sections for forming a compound system of two colliding spheres and through calculations of electron transfer cross sections. We find that it is important to account for dielectric properties and finite sphere sizes in such calculations, which for example may be useful for describing the evolution, growth, and dynamics of nanometer sized dielectric objects such as molecular clusters or dust grains in different environments including astrophysical ones.

Visa alla publikationer av Henning Zettergren vid Stockholms universitet

Senast uppdaterad: 2 januari 2018

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