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Hennies, Franz
Alternative names
Publications (10 of 23) Show all publications
Nilson, K., Åhlund, J., Shariati, M.-N., Schiessling, J., Palmgren, P., Brena, B., . . . Puglia, C. (2012). Potassium-intercalated H2Pc films: Alkali-induced electronic and geometrical modifications. Journal of Chemical Physics, 137(4), 044708
Open this publication in new window or tab >>Potassium-intercalated H2Pc films: Alkali-induced electronic and geometrical modifications
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2012 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, no 4, p. 044708-Article in journal (Refereed) Published
Abstract [en]

X-ray spectroscopy studies of potassium intercalated metal-free phthalocyanine multilayers adsorbed on Al(110) have been undertaken. Photoelectron spectroscopy measurements show the presence of several charge states of the molecules upon K intercalation, due to a charge transfer from the alkali. In addition, the comparison of valence band photoemission spectra with the density functional theory calculations of the density of states of the H2Pc anion indicates a filling of the formerly lowest unoccupied molecular orbital by charge transfer from the alkali. This is further confirmed by x-ray absorption spectroscopy (XAS) studies, which show a decreased density of unoccupied states. XAS measurements in different experimental geometries reveal that the molecules in the pristine film are standing upright on the surface or are only slightly tilted away from the surface normal but upon K intercalation, the molecular orientation is changed in that the tilt angle of the molecules increases.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-173385 (URN)10.1063/1.4738755 (DOI)000307611500056 ()
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
Rubensson, J.-E., Pietzsch, A. & Hennies, F. (2012). Vibrationally resolved resonant inelastic soft X-ray scattering spectra of free molecules. Journal of Electron Spectroscopy and Related Phenomena, 185(8-9), 294-300
Open this publication in new window or tab >>Vibrationally resolved resonant inelastic soft X-ray scattering spectra of free molecules
2012 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 185, no 8-9, p. 294-300Article in journal (Refereed) Published
Abstract [en]

The brilliance of modern synchrotron radiation sources and capabilities of new instrumentation facilitate molecular resonant inelastic soft X-ray scattering with high spectral quality. Especially, energy resolution of vibrational fine structure allows for a detailed analysis, providing information about the dynamic coupling between nuclear and electronic degrees of freedom. After a brief historical account and a short qualitative comparison between the radiative and non-radiative decay channels we review the recent results for the oxygen molecule. Nuclear wavepacket dynamics in bound and unbound states is studied, and in the latter case spatial quantum beats are observed as the dissociation proceeds via two different electronic states. A new internal spin-coupling conservation rule is established, whereas a commonly accepted selection rule based on orbital symmetry is violated.

Keywords
Resonant inelastic X-ray scattering, Spectroscopy, Molecular physics, Dynamics, Symmetry
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-182768 (URN)10.1016/j.elspec.2012.05.003 (DOI)000308627700016 ()
Available from: 2012-10-17 Created: 2012-10-15 Last updated: 2017-12-07Bibliographically approved
Yu, S., Ahmadi, S., Sun, C., Schulte, K., Pietzsch, A., Hennies, F., . . . Göthelid, M. (2011). Crystallization-Induced Charge-Transfer Change in TiOPc Thin Films Revealed by Resonant Photoemission Spectroscopy. The Journal of Physical Chemistry C, 115(30), 14969-14977
Open this publication in new window or tab >>Crystallization-Induced Charge-Transfer Change in TiOPc Thin Films Revealed by Resonant Photoemission Spectroscopy
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2011 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 30, p. 14969-14977Article in journal (Refereed) Published
Abstract [en]

Organic semiconductors usually demonstrate crystal structure dependent electronic properties, and through precise control of film structure, the performance of novel organic electronic devices can be greatly improved. Understanding the crystal structure dependent charge-transfer mechanism thus becomes critical. In this work, we have prepared amorphous titanyl phthalocyanine films by vacuum molecular beam evaporation and have further crystallized them through vacuum annealing. In the crystalline phase, an excited electron is rapidly transferred into neighboring molecules; while in the amorphous phase, it is mainly localized and recombines with the core hole as revealed by resonant photoemission spectroscopy (RPES). The fast electron transfer time is determined to be around 16 fs in the crystalline film, which is in good agreement with the charge-transfer hopping time estimated from the best device performance reported. The crystallized film shows more p-type characteristics than the amorphous with all the energy levels shifting toward the vacuum level. However, the greatly improved charge transfer is assigned to the molecular orbital coupling rather than this shift. From density functional theory and RPES, we specify the contribution of two differently coordinated nitrogen atoms (N2c and N3c) to the experimental results and illustrate that the N3c related orbital has experienced a dramatic change, which is keenly related to the improved charge transfer.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-157013 (URN)10.1021/jp1100363 (DOI)000293192100067 ()
Available from: 2011-08-16 Created: 2011-08-15 Last updated: 2017-12-08Bibliographically approved
Sun, Y.-P., Pietzsch, A., Hennies, F., Rinkevicius, Z., Karlsson, H. O., Schmitt, T., . . . Rubensson, J.-E. (2011). Internal symmetry and selection rules in resonant inelastic soft x-ray scattering. Journal of Physics B: Atomic, Molecular and Optical Physics, 44(16), 161002
Open this publication in new window or tab >>Internal symmetry and selection rules in resonant inelastic soft x-ray scattering
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2011 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 44, no 16, p. 161002-Article in journal (Refereed) Published
Abstract [en]

Resonant inelastic soft x-ray scattering spectra excited at the dissociative 1 sigma(g) -> 3 sigma(u) resonance in gas-phase O(2) are presented and discussed in terms of state-of-the-art molecular theory. A new selection rule due to internal spin coupling is established, facilitating a deep analysis of the valence excited final states. Furthermore, it is found that a commonly accepted symmetry selection rule due to orbital parity breaks down, as the core hole and excited electron swap parity, thereby opening the symmetry forbidden 3 sigma(g) decay channel.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-159484 (URN)10.1088/0953-4075/44/16/161002 (DOI)000294890800002 ()
Available from: 2011-10-03 Created: 2011-10-03 Last updated: 2017-12-08Bibliographically approved
Sun, Y.-P. -., Hennies, F., Pietzsch, A., Kennedy, B., Schmitt, T., Strocov, V. N., . . . Foehlisch, A. (2011). Intramolecular soft modes and intermolecular interactions in liquid acetone. Physical Review B. Condensed Matter and Materials Physics, 84(13), 132202
Open this publication in new window or tab >>Intramolecular soft modes and intermolecular interactions in liquid acetone
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2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 13, p. 132202-Article in journal (Refereed) Published
Abstract [en]

Resonant inelastic x-ray scattering spectra excited at the O1s(-1)pi* resonance of liquid acetone are presented. Scattering to the electronic ground state shows a resolved vibrational progression where the dominant contribution is due to the C-O stretching mode, thus demonstrating a unique sensitivity of the method to the local potential energy surface in complex molecular systems. For scattering to electronically excited states, soft vibrational modes and, to a smaller extent, intermolecular interactions give a broadening, which blurs the vibrational fine structure. It is predicted that environmental broadening is dominant in aqueous acetone.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-161934 (URN)10.1103/PhysRevB.84.132202 (DOI)000296372300001 ()
Available from: 2011-11-23 Created: 2011-11-21 Last updated: 2017-12-08Bibliographically approved
Pietzsch, A., Sun, Y.-P. -., Hennies, F., Rinkevicius, Z., Karlsson, H., Schmitt, T., . . . Gel'mukhanov, F. (2011). Spatial Quantum Beats in Vibrational Resonant Inelastic Soft X-Ray Scattering at Dissociating States in Oxygen. Physical Review Letters, 106(15), 153004-1-153004-4
Open this publication in new window or tab >>Spatial Quantum Beats in Vibrational Resonant Inelastic Soft X-Ray Scattering at Dissociating States in Oxygen
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2011 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 15, p. 153004-1-153004-4Article in journal (Refereed) Published
Abstract [en]

Resonant inelastic soft x-ray scattering (RIXS) spectra excited at the 1 sigma(g) -> 3 sigma(u) resonance in gas-phase O-2 show excitations due to the nuclear degrees of freedom with up to 35 well-resolved discrete vibronic states and a continuum due to the kinetic energy distribution of the separated atoms. The RIXS profile demonstrates spatial quantum beats caused by two interfering wave packets with different momenta as the atoms separate. Thomson scattering strongly affects both the spectral profile and the scattering anisotropy.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-153939 (URN)10.1103/PhysRevLett.106.153004 (DOI)000289525300005 ()
Available from: 2011-05-23 Created: 2011-05-23 Last updated: 2017-12-11Bibliographically approved
Århammar, C., Pietzsch, A., Bock, N., Holmström, E., Araujo, C. ., Gråsjö, J., . . . Ahuja, R. (2011). Unveiling the complex electronic structure of amorphous metal oxides. Proceedings of the National Academy of Sciences of the United States of America, 108(16), 6355-6360
Open this publication in new window or tab >>Unveiling the complex electronic structure of amorphous metal oxides
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2011 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 108, no 16, p. 6355-6360Article in journal (Refereed) Published
Abstract [en]

Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.

Keywords
stochastic quench, X-ray absorption spectroscopy, ab initio, coating
National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-153224 (URN)10.1073/pnas.1019698108 (DOI)000289680400011 ()
Available from: 2011-05-09 Created: 2011-05-09 Last updated: 2018-06-26Bibliographically approved
Yu, S., Ahmadi, S., Zuleta, M., Tian, H., Schulte, K., Pietzsch, A., . . . Göthelid, M. (2010). Adsorption geometry, molecular interaction, and charge transfer of triphenylamine-based dye on rutile TiO2(110). Journal of Chemical Physics, 133(22), 224704
Open this publication in new window or tab >>Adsorption geometry, molecular interaction, and charge transfer of triphenylamine-based dye on rutile TiO2(110)
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2010 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, no 22, p. 224704-Article in journal (Refereed) Published
Abstract [en]

The fast development of new organic sensitizers leads to the need for a better understanding of the complexity and significance of their adsorption processes on TiO2 surfaces. We have investigated a prototype of the triphenylamine-cyanoacrylic acid (donor-acceptor) on rutile TiO2 (110) surface with special attention on the monolayer region. This molecule belongs to the type of dye, some of which so far has delivered the record efficiency of 10%-10.3% for pure organic sensitizers [W. Zeng, Y. Cao, Y. Bai, Y. Wang, Y. Shi, M. Zhang, F. Wang, C. Pan, and P. Wang, Chem. Mater. 22, 1915 (2010)]. The molecular configuration of this dye on the TiO2 surface was found to vary with coverage and adopt gradually an upright geometry, as determined from near edge x-ray absorption fine structure spectroscopy. Due to the molecular interaction within the increasingly dense packed layer, the molecular electronic structure changes systematically: all energy levels shift to higher binding energies, as shown by photoelectron spectroscopy. Furthermore, the investigation of charge delocalization within the molecule was carried out by means of resonant photoelectron spectroscopy. A fast delocalization (similar to 1.8 fs) occurs at the donor part while a competing process between delocalization and localization takes place at the acceptor part. This depicts the "push-pull" concept in donor-acceptor molecular system in time scale.

National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:uu:diva-144503 (URN)10.1063/1.3509389 (DOI)000285477800019 ()
Available from: 2011-02-01 Created: 2011-01-31 Last updated: 2017-12-11Bibliographically approved
Hennies, F., Pietzsch, A., Berglund, M., Föhlisch, A., Schmitt, T., Strocov, V., . . . Rubensson, J.-E. (2010). Resonant Inelastic Scattering Spectra of Free Molecules with Vibrational Resolution. Physical Review Letters, 104(19), 193002
Open this publication in new window or tab >>Resonant Inelastic Scattering Spectra of Free Molecules with Vibrational Resolution
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2010 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, no 19, p. 193002-Article in journal (Refereed) Published
Abstract [en]

Inelastic x-ray scattering spectra excited at the 1s(-1) pi* resonance of gas phase O-2 have been recorded with an overall energy resolution that allows for well-resolved vibrational progressions. The nuclear wave packet dynamics in the intermediate state is reflected in vibrational excitations of the electronic ground state, and by fine-tuning the excitation energy the dissociation dynamics in the predissociative B' (3) Pi(g) final state is controlled.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-136431 (URN)10.1103/PhysRevLett.104.193002 (DOI)000277699600016 ()
Available from: 2010-12-13 Created: 2010-12-13 Last updated: 2017-12-11Bibliographically approved
Mårtensson, N., Preobrajenski, A. B. & Hennies, F. (2009). Bonding and dynamics of surface systems probed by soft X-rays. The European Physical Journal - Special Topics, 169(1), 133-140
Open this publication in new window or tab >>Bonding and dynamics of surface systems probed by soft X-rays
2009 (English)In: The European Physical Journal - Special Topics, ISSN 1951-6355, Vol. 169, no 1, p. 133-140Article, review/survey (Refereed) Published
Abstract [en]

We review some aspects of the investigation of surface systems with soft X-rays. Examples are presented, showing how core level spectroscopies provide detailed information on the structure, bonding and chemistry of adsorbates and thin layers on surfaces. Core level spectroscopies employed at high brilliance synchrotron light sources allow furthermore access to electron dynamics in the attosecond domain, as we demonstrate for the core hole clock method.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-142327 (URN)10.1140/epjst/e2009-00983-x (DOI)000264560900020 ()
Available from: 2011-01-14 Created: 2011-01-13 Last updated: 2012-02-24Bibliographically approved
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