Search

Your search keyword '"Tolan M"' showing total 488 results
Start Over Author "Tolan M"
488 results on '"Tolan M"'

3. A portable on-Axis laser-heating system for near-90° X-ray spectroscopy: Application to ferropericlase and iron silicide

Author

Spiekermann, G, Kupenko, I, Petitgirard, S, Harder, M, Nyrow, A, Weis, C, Albers, C, Biedermann, N, Libon, L, Sahle, C, Cerantola, V, Glazyrin, K, Konopkova, Z, Sinmyo, R, Morgenroth, W, Sergueev, I, Yava, H, Dubrovinsky, L, Tolan, M, Sternemann, C, Wilke, M, Spiekermann G, Kupenko I, Petitgirard S, Harder M, Nyrow A, Weis C, Albers C, Biedermann N, Libon L, Sahle CJ, Cerantola V, Glazyrin K, Konopkova Z, Sinmyo R, Morgenroth W, Sergueev I, Yava H, Dubrovinsky L, Tolan M, Sternemann C, Wilke M, Spiekermann, G, Kupenko, I, Petitgirard, S, Harder, M, Nyrow, A, Weis, C, Albers, C, Biedermann, N, Libon, L, Sahle, C, Cerantola, V, Glazyrin, K, Konopkova, Z, Sinmyo, R, Morgenroth, W, Sergueev, I, Yava, H, Dubrovinsky, L, Tolan, M, Sternemann, C, Wilke, M, Spiekermann G, Kupenko I, Petitgirard S, Harder M, Nyrow A, Weis C, Albers C, Biedermann N, Libon L, Sahle CJ, Cerantola V, Glazyrin K, Konopkova Z, Sinmyo R, Morgenroth W, Sergueev I, Yava H, Dubrovinsky L, Tolan M, Sternemann C, and Wilke M

Abstract

A portable IR fiber laser-heating system, optimized for X-ray emission spectroscopy (XES) and nuclear inelastic scattering (NIS) spectroscopy with signal collection through the radial opening of diamond anvil cells near 90°with respect to the incident X-ray beam, is presented. The system offers double-sided on-Axis heating by a single laser source and zero attenuation of incoming X-rays other than by the high-pressure environment. A description of the system, which has been tested for pressures above 100GPa and temperatures up to 3000K, is given. The XES spectra of laser-heated Mg0.67Fe0.33O demonstrate the potential to map the iron spin state in the pressure-Temperature range of the Earth's lower mantle, and the NIS spectra of laser-heated FeSi give access to the sound velocity of this candidate of a phase inside the Earth's core. This portable system represents one of the few bridges across the gap between laser heating and high-resolution X-ray spectroscopies with signal collection near 90°.

Published
2020

4. Fe3+ -hosting carbon phases in the deep Earth

Author

Albers, C, Sakrowski, R, Libon, L, Spiekermann, G, Winkler, B, Schmidt, C, Bayarjargal, L, Cerantola, V, Chariton, S, Giordano, N, Gretarsson, H, Kaa, J, Liermann, H, Sundermann, M, Thiering, N, Tolan, M, Wilke, M, Christian Sternemann, A, Christian Albers, Robin Sakrowski, Lélia Libon, Georg Spiekermann, Björn Winkler, Christian Schmidt, Lkhamsuren Bayarjargal, Valerio Cerantola, Stella Chariton, Nico Giordano, Hlynur Gretarsson, Johannes Kaa, Hanns-Peter Liermann, Martin Sundermann, Nicola Thiering, Metin Tolan, Max Wilke, and Christian Sternemann, Albers, C, Sakrowski, R, Libon, L, Spiekermann, G, Winkler, B, Schmidt, C, Bayarjargal, L, Cerantola, V, Chariton, S, Giordano, N, Gretarsson, H, Kaa, J, Liermann, H, Sundermann, M, Thiering, N, Tolan, M, Wilke, M, Christian Sternemann, A, Christian Albers, Robin Sakrowski, Lélia Libon, Georg Spiekermann, Björn Winkler, Christian Schmidt, Lkhamsuren Bayarjargal, Valerio Cerantola, Stella Chariton, Nico Giordano, Hlynur Gretarsson, Johannes Kaa, Hanns-Peter Liermann, Martin Sundermann, Nicola Thiering, Metin Tolan, Max Wilke, and and Christian Sternemann

Abstract

Iron-bearing carbonates play an important role in Earth's carbon cycle. Owing to their stability at mantle conditions, recently discovered iron carbonates with tetrahedrally coordinated carbon atoms are candidates for carbon storage in the deep Earth. The carbonates' iron oxidation and spin state at extreme pressure and temperature conditions contribute to the redox conditions and element partitioning in the deep mantle. By laser heating FeCO3 at pressures of about 83 GPa, Fe43+C3O12 and Fe22+Fe23+C4O13 were synthesized and then investigated by x-ray emission spectroscopy to elucidate their spin state, both in situ and temperature quenched. Our experimental results show both phases in a high-spin state at all pressures and over the entire temperature range investigated, i.e., up to 3000 K. The spin state is conserved after temperature quenching. A formation path is favored where Fe43+C3O12 forms first and then reacts to Fe22+Fe23+C4O13, most likely accompanied by the formation of oxides. Density functional theory calculations of Fe22+Fe23+C4O13 at 80 GPa confirm the experimental findings with both ferric and ferrous iron in high-spin state with antiferromagnetic order at 80 GPa. As the intercrystalline cation partitioning between the Fe-bearing carbonates and the surrounding perovskite and ferropericlase depends on the spin state of the iron, an understanding of the redox conditions prevalent in subducted slab regions in the lower mantle has to take the latter into account. Especially, Fe22+Fe23+C4O13 may play a key role in subducted material in the lower mantle, potentially with a similar role as silicate perovskite.

Published
2022

7. Connecting structurally and dynamically detected signatures of supramolecular Debye liquids.

Author

Büning, T., Lueg, J., Bolle, J., Sternemann, C., Gainaru, C., Tolan, M., and Böhmer, R.

Subjects
ALCOHOLS (Chemical class), HALIDES, ORGANIC compounds, HALOGEN compounds, OXYGEN
Abstract

The monohydroxy alcohol 2-ethyl-1-hexanol mixed with the halogen-substituted alkyl halides 2-ethyl- 1-hexyl chloride and 2-ethyl-1-hexyl bromide was studied using synchrotron-based x-ray scattering. In the diffraction patterns, an oxygen-related prepeak appears. The concentration dependence of its intensity, shape, and position indicates that the formation of the hydrogen-bonded associates of monohydroxy alcohols is largely hindered by the halogen alkane admixture. Using dielectric spectroscopy and high-resolution rheology on the same liquid mixtures, it is shown that these structural features are correlated with the relaxation mechanisms giving rise to supramolecular low-frequency dynamics. [ABSTRACT FROM AUTHOR]

Published
2017
Full Text
View/download PDF

11. Irish thoracic society: Proceedings of Meeting held November, 1691 in Belfast

Author

Smyth, E. T., Wright, S. C., Sinnamon, D. G., Evans, A. E., MacMahon, J., Loughrey, C., Riley, M., Varghese, G., Buick, J. B., Lowry, R. C., Costello, R., McNicholas, W. T., Quigley, C., Long, M., Conlon, P., Walker, F., Fitzgerald, P., O’Neill, S. J., O’Connor, C. M., Rook, G., FitzGerald, M. X., Subbareddy, K., Luke, D., McGovern, E., Karim, A. F., Luke, D. A., Hogan, F. P., O’Sullivan, M. P., O’Sullivan, M., Grant, W., Walsh, M., Reynolds, S. P., Phillips, A., Richards, R., Jones, K. P., Cunnane, G., Kelly, P., Corcoran, P., Clancy, L., Lyons, D. J., Keating, J., Mulcahy, F., Hartley, P., Goodman, P. G., Houlihan, K. P., Singh, H. P., Aherne, T., Attwood, S. E. A., Wood, A. E., Sweeney, J. P., Hegarty, V., Scott, T., Keane, C., Walsh, J. B., Coakley, D., Donnelly, S., Robinson, C., Zamani, A., McGregor, I., Gordon, M., Steedman, D., Pollock, A., Haslett, C., Cordon, S. M., Elborn, J. S., Rayner, R. J., Hiller, E. J., Shale, D. J., Sinclair, H., Allwright, S., Prichard, J., Macleod, D., Vanderputten, W., O’Briann, D. S., Prichard, J. S., Khan, A., Power, C. K., Morris, A. M., Sreenan, S. K., Burke, C. M., Power, C., Byrne, P., Jarrett, S. J., Hogan, T., Hurson, B., Poulter, L., Clarkson, K., O’Connell, F., Norris, A., Coffey, F., Sreenan, S., Burke, C., MacManus, K., Ritchie, A., Gibbons, J., Stevenson, M., McAuley, W. J., McGuigan, J., Gibbons, J. R., Whiteside, M., Tolan, M., Danton, M., Tolan, M., McGuigan, J. A., Gibbons, J. R. P., Clements, W. B., Kinley, J. K., Johnston, C. F., Gibbons, T. R. P., Buchanan, K. D., Ogunnaike, H. O., Al-Jilaihawi, A. N., Prakash, D., Ghareeb, E. M., Ritchie, A. J., Cosgrove, A. P., O’Donnell, A. F., Neligan, M. C., O’Connor, B. J., Barnes, P. J., O’Connor, B., Donaghy, D., Mulloy, E., McNicholas, W., Northridge, D., Henderson, E., Stanford, C. F., Nichols, P., Dargie, H., Stewart, E. J., Cinnamond, M. J., Nicholls, D. P., Moore, H., Finnegan, P., Gibson, G., Abernethy, E., Plant, L., Bredin, C. P., Murray, J. G., Breathnach, E., Eustace, S., Phelan, N., and Ennis, J. T.

Published
1992
Full Text
View/download PDF

15. Structural characterization of oxidized allotaxially grown CoSi(sub)2 layers by x-ray scattering

Author

Kaendler, I.D., Seeck, O.H., Schlomka, J.-P., Tolan, M., Press, W., Stettner, J., Kappius, L., Dieker, C., and Mantl, S.

Subjects
Epitaxy -- Analysis, Crystals -- Structure, Silicides -- Research, X-rays -- Scattering, Physics
Abstract

Results show that oxidation time increases during crystal growth affect roughness of the crystal layers and the oxidation growth process itself is limited by diffusion process.

Published
2000

16. Interdiffusion in NiMnSb/V/NiMnSb: x-ray and neutron reflectivity investigation of ion beam sputtered trilayer systems

Author

Schlomka, J.-P., Tolan, M., Press, W., Fitzsimmons, M.R., Siebrecht, R., Schubert, D.W., and Simon, P.

Subjects
Diffusion -- Research, Semiconductors -- Diffusion, Thin films, Multilayered -- Research, Physics
Abstract

Vibrating sample magnetometry, x-ray and neutron reflectivity were used in studying the new NiMnSb/V/NiMnSb trilayer system on MgO(OO1). Results indicated the presence of a coercive field Hc equal to 23 Oe and a hysteresis loop similar to that of an uncoupled ferromagnet. Interface roughnesses of 10 angstroms and significant interdiffusion at the NiMnSb/V interfaces were also detected. The latter observation may explain the weak magnetoresistance effect in other similar multilayer systems.

Published
1999

17. Pressure driven spin transition in siderite and magnesiosiderite single crystals

Author

Weis, C, Sternemann, C, Cerantola, V, Sahle, C, Spiekermann, G, Harder, M, Forov, Y, Kononov, A, Sakrowski, R, Yavas, H, Tolan, M, Wilke, M, Weis C, Sternemann C, Cerantola V, Sahle CJ, Spiekermann G, Harder M, Forov Y, Kononov A, Sakrowski R, Yavas H, Tolan M, Wilke M, Weis, C, Sternemann, C, Cerantola, V, Sahle, C, Spiekermann, G, Harder, M, Forov, Y, Kononov, A, Sakrowski, R, Yavas, H, Tolan, M, Wilke, M, Weis C, Sternemann C, Cerantola V, Sahle CJ, Spiekermann G, Harder M, Forov Y, Kononov A, Sakrowski R, Yavas H, Tolan M, and Wilke M

Abstract

Iron-bearing carbonates are candidate phases for carbon storage in the deep Earth and may play an important role for the Earth's carbon cycle. To elucidate the properties of carbonates at conditions of the deep Earth, we investigated the pressure driven magnetic high spin to low spin transition of synthetic siderite FeCO3 and magnesiosiderite (Mg0.74Fe0.26)CO3 single crystals for pressures up to 57 GPa using diamond anvil cells and x-ray Raman scattering spectroscopy to directly probe the iron 3d electron configuration. An extremely sharp transition for siderite single crystal occurs at a notably low pressure of 40.4 ± 0.1 GPa with a transition width of 0.7 GPa when using the very soft pressure medium helium. In contrast, we observe a broadening of the transition width to 4.4 GPa for siderite with a surprising additional shift of the transition pressure to 44.3 ± 0.4 GPa when argon is used as pressure medium. The difference is assigned to larger pressure gradients in case of argon. For magnesiosiderite loaded with argon, the transition occurs at 44.8 ± 0.8 GPa showing similar width as siderite. Hence, no compositional effect on the spin transition pressure is observed. The spectra measured within the spin crossover regime indicate coexistence of regions of pure high- and low-spin configuration within the single crystal.

Published
2017

21. X-ray characterization of buried allotaxially grown CoSi(sub2) layers in Si(100)

Author

Zimmermann, U., Schlomka, J.P., Tolan. M., Stettner, J., Press, W., Hacke, M., and Mantle, S.

Subjects
Thin films -- Research, Semiconductor films -- Research, Electron microscopy -- Usage, Physics
Abstract

An x-ray investigation of the interface morphology and lattice parameters of buried expitaxial CoSi(sub2) layers in Si(100) is reported. CoSi(sub2) interfaces were smoothened by an annealing step at 115 degrees C. The perpendicular lattice parameter is between a free relaxed and a pseudomorphic structure, and a linear contraction was obtained. However the opposite effect was revealed for the in-plane lattice mismatch.

Published
1998

27. X-ray diffraction from laterally structured surfaces: crystal truncation rods

Author

Tolan, M., Press, W., Brinkop, F., and Kotthaus, J.P.

Subjects
Gallium arsenide -- Research, X-rays -- Scattering, Physics
Abstract

X-ray diffraction studies of single-crystalline GaAs(001) surface gratings using three-crystal diffractometer reveal that lateral structures can be studied by non-destructive X-ray scattering method. The measurements obtained by the X-ray diffraction studies enable the calculation of the crystal truncation rod (CTR). The diffraction studies did not reveal any dynamical resonance effect.

Published
1994

29. Intermolecular interactions in highly concentrated protein solutions upon compression and the role of the solvent.

Author

Grobelny, S., Erlkamp, M., Möller, J., Tolan, M., and Winter, R.

Subjects
INTERMOLECULAR interactions, PROTEIN solubility, SOLVENTS, PROTEIN structure, X-ray scattering
Abstract

The influence of high hydrostatic pressure on the structure and protein-protein interaction potential of highly concentrated lysozyme solutions up to about 370 mg ml-1 was studied and analyzed using small-angle X-ray scattering in combination with a liquid-state theoretical approach. In the concentration region below 200 mg ml-1 , the interaction parameters of lysozyme solutions are affected by pressure in a nonlinear way, which is probably due to significant changes in the structural properties of bulk water, i.e., due to a solvent-mediated effect. Conversely, for higher concentrated protein solutions, where hydration layers below ~4 water molecules are reached, the interaction potential turns rather insensitive to compression. The onset of transient (dynamic) clustering is envisaged in this concentration range. Our results also show that pressure suppresses protein nucleation, aggregation and finally crystallization in supersaturated condensed protein solutions. These findings are of importance for controlling and fine-tuning protein crystallization. Moreover, these results are also important for understanding the high stability of highly concentrated protein solutions (as they occur intracellularly) in organisms thriving under hydrostatic pressure conditions such as in the deep sea, where pressures up to the kbar-level are reached. [ABSTRACT FROM AUTHOR]

Published
2014
Full Text
View/download PDF

30. Bulk sensitive determination of the Fe3+/Fe-Tot-ratio in minerals by Fe L-2/3-edge X-ray Raman scattering

Author

Nyrow, A, Sternemann, C, Tse, J, Weis, C, Sahle, C, Mende, K, Wieland, D, Cerantola, V, Gordon, R, Spiekermann, G, Regier, T, Wilke, M, Tolan, M, Nyrow A, Sternemann C, Tse JS, Weis C, Sahle CJ, Mende K, Wieland DCF, Cerantola V, Gordon RA, Spiekermann G, Regier T, Wilke M, Tolan M, Nyrow, A, Sternemann, C, Tse, J, Weis, C, Sahle, C, Mende, K, Wieland, D, Cerantola, V, Gordon, R, Spiekermann, G, Regier, T, Wilke, M, Tolan, M, Nyrow A, Sternemann C, Tse JS, Weis C, Sahle CJ, Mende K, Wieland DCF, Cerantola V, Gordon RA, Spiekermann G, Regier T, Wilke M, and Tolan M

Abstract

We present the first measurements of the iron L2/3-edge of the compounds FeO, Fe2O3, and Fe3O4 at ambient pressure and of FeCO3 at high pressures of 2.4 and 40 GPa using a diamond anvil cell by X-ray Raman scattering spectroscopy, a bulk sensitive probe of soft X-ray absorption edges making use of hard X-rays. We show that the spectral shape of the Fe L2/3-edge can be analyzed quantitatively to reveal the oxidation state of iron in matter. Consequently, in situ X-ray Raman scattering spectroscopy at the iron L-edge at high pressure and temperature opens exciting perspectives to characterize the local coordination, oxidation, and spin state of iron at high pressure and temperature, conditions that are of relevance for e.g. geological sciences or chemical processing.

Published
2016

31. Infective endocarditis: a retrospective cohort study

Author

O’Connor, C T, primary, O’Rourke, S, additional, Buckley, A, additional, Murphy, R, additional, Crean, P, additional, Foley, B, additional, Maree, A, additional, Ryan, R, additional, Tolan, M, additional, Young, V, additional, O’Connell, B, additional, and Daly, C, additional

Published
2019
Full Text
View/download PDF

36. New deal not satisfactory for cardiothoracic surgery

Author

Alkhulaifi, A, Allen, S M, Anderson, J R, Argano, V, Austin, C, Barlow, C, Barnard, S, Barron, D, Berrisford, R, Billing, S, Brackenbury, E, Braidley, P C, Bridgewater, B J M, Briffa, N P Buchan, Butler, J, Cale, A R J, Carr, H M H Ciulli, Clark, S, Cooper, G J, Craig, S, Danton, M, Dihimis, W C, Duffy, J, Duncan, A, Gaer, J, Gibson, G, Griffin, S C, Hasan, R I R, Hopkinson, D, Hornick, P, Hunter, S, John, L C H, Kanagaseay, R, Kuo, J, Langley, S, Levine, A J, McNamara, V, Oakley, E El, Ohri, S K, O'Keefe, P A, O'Regan, D, Parry, G W, Pathi, V L, Peters, P, Prendergast, B, Ridley, P D, Ritchie, A J, Roxburgh, J C, Sharpe, D A C, de Souza, A C, Steyn, R, Tan, K K, Tolan, M, Trevidi, U H, Tsang, G M K, Tsui, S, Underwood, M J, Unsworth-White, M J, Uppal, R, Van Doorn, C, Waller, D A, Weerasena, N, and Young, V

Published
1995

38. Pressure stability of the first hydration shell of yttrium in aqueous YCl3 solution.

Author

Elbers, M., Sternemann, C., Julius, K., Paulus, M., Surmeier, G., König, N., Nase, J., Bolle, J., Wagner, R., Irifune, T., and Tolan, M.

Subjects
EXTENDED X-ray absorption fine structure, AQUEOUS solutions, YTTRIUM, HYDRATION, HYDROSTATIC pressure, X-ray absorption, PRESSURE
Abstract

The pressure stability of the first hydration shell of Y 3 + ions in aqueous solution has been investigated by means of extended x-ray absorption fine-structure spectroscopy at the yttrium K-edge for hydrostatic pressures up to 4.5 kbar and concentrations between 1 M and 2.5 M. We find approximately 8.4 water molecules surrounding the yttrium cation at a mean distance of 2.370 Å at ambient conditions, independent on the concentration. The yttrium hydration shell has a low compressibility in the order of (− 3.8 ± 0.7) × 10 − 4 Å kbar − 1 emphasizing its pressure stability in the kbar range. At the studied conditions, no indication for chloride complexation was observed. [ABSTRACT FROM AUTHOR]

Published
2020
Full Text
View/download PDF

42. Influence of chromium as carbide forming doping element on the diamond retention in diamond tools

Author

Tillmann, W., Tolan, M., Lopes-Dias, N. F., Zimpel, M., Ferreira, M., and Paulus, M.

Subjects
Diamond tools, interface reactions, diamond retention, diamond-metal composites, metal diamond interface, SEM - analyses
Abstract

Diamond tools are widely used in drill tools, wire saws or circular saws to machine very hard materials such as concrete or natural stone in the construction as well as extractive industries. The mechanical and physical properties, such of these materials call for high requirements concerning the diamond tools. In particular, the bonding between the diamond particles and the metallic binder is an essential criterion for the tool quality. It is known that the type and strength of bonding is influenced by the diamond-metal interaction that occurs during the sintering process. Depending on the element used as a metallic binder, different thermally induced chemical reactions between the diamond and the metallic matrix take place. These reactions are (1) carbide formation, (2) graphite formation, and (3) inert behavior. However, there is still a high demand concerning the research of the diamond-metal interaction influenced by a carbide forming element. In this work, chromium as a carbide-forming element was used as a doping agent in order to increase the diamond retention in diamond tools. The elements iron, cobalt and nickel were selected as single metallic components due to their catalytic influence on the graphitization of diamonds; whereas three metallic matrix systems were additionally doped with 15% chromium. The samples were sintered by hot pressing. Furthermore, half of the samples were thermally treated in order to ensure a stronger thermal induction of the interfacial reactions. In order to analyze the bonding behavior of the diamonds in the metal matrix, the samples were broken and the interfacial area was analyzed by means scanning of electron microscopy. These experimental studies show an influence of the carbide-forming doping agent on the diamond-metal interaction., International Conference on Stone and Concrete Machining (ICSCM), Vol 3 (2015)

Published
2015
Full Text
View/download PDF

44. Infective endocarditis: a retrospective cohort study.

Author

O'Connor, C T, O'Rourke, S, Buckley, A, Murphy, R, Crean, P, Foley, B, Maree, A, Ryan, R, Tolan, M, Young, V, O'Connell, B, and Daly, C

Subjects
MEDICAL microbiology, INFECTIVE endocarditis, COHORT analysis, CARDIAC infections, ENDOCARDITIS, RETROSPECTIVE studies
Abstract

Background Infective endocarditis (IE) is a potentially life-threatening infection of the heart's endocardial surface. Despite advances in the diagnosis and management of IE, morbidity and mortality remain high. Aim To characterize the demographics, bacteriology and outcomes of IE cases presenting to an Irish tertiary referral centre. Design Retrospective cohort study. Methods Patients were identified using Hospital Inpatient Enquiry and Clinical Microbiology inpatient consult data, from January 2005 to January 2014. Patients were diagnosed with IE using Modified Duke Criteria. Standard Bayesian statistics were employed for analysis and cases were compared to contemporary international registries. Results Two hundred and two patients were diagnosed with IE during this period. Mean age 54 years. Of these, 136 (67%) were native valve endocarditis (NVE), 50 (25%) were prosthetic valve endocarditis (PVE) and 22 (11%) were cardiovascular implantable electronic device-associated endocarditis. Culprit organism was identified in 176 (87.1%) cases and Staphylococcal species were the most common (57.5%). Fifty-nine per cent of NVE required surgery compared to 66% of PVE. Mean mortality rate was 17.3%, with NVE being the lowest (12.5%) and PVE the highest (32%). Increasing age was also associated with increased mortality. Fifty-three (26.2%) patients had embolic complications. Conclusions This Irish cohort exhibited first-world demographic patterns comparable to those published in contemporary international literature. PVE required surgery more often and was associated with higher rates of mortality than NVE. Embolic complications were relatively common and represent important sequelae, especially in the intravenous drug user population. It is also pertinent to aggressively treat older cohorts as they were associated with increased mortality. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

45. The Ba 4d-4f giant dipole resonance in complex Ba/Si compounds

Author

Sahle, C.J., Sternemann, C., Sternemann, H., Tse, J.S., Gordon, R.A., Desgreniers, S., Maekawa, S., Yamanaka, S., Lehmkuehler, F., Wieland, D.C.F., Mende, K., Huotari, S., and Tolan, M.

Subjects
ddc:539.1
Abstract

The shape of the Ba 4d–4f giant dipole resonance is studied for Ba atoms embedded inside complex Si networks covering structures consisting of Si nanocages and nanotubes, i.e. the clathrate Ba8Si46, the complex compound BaSi6, and the semiconducting BaSi2. Here, non-resonant x-ray Raman scattering is used to investigate confinement effects on the shape of the giant resonance in the vicinity of the Ba NIV, V-edge. The distinct momentum transfer dependence of the spectra is analyzed and discussed. The measurements are compared to calculations of the giant resonance within time-dependent local density approximation in the dipole limit. No modulation of the giant resonance\'s shape for Ba atoms confined in different local environments was observed, in contrast to the calculations. The absence of such shape modulation for complex Ba/Si compounds is discussed providing important implications for further studies of giant resonance phenomena utilizing both theory and experiment.

Published
2014
Full Text
View/download PDF

49. Irish society of rheumatology and rehabilitation: Meeting held on Friday, 25th November, 1983

Author

Taggart, A. J., Desai, S. M., Iveson, J. M., Verow, P. W., Tolan, M. J., Comerford, F. R., Bresnlhan, Barry, FitzGerald, Oliver, Masterson, James, Templeton, J., Graham, K., Roberts, Stanley, Hassan, J., Hanly, J., Whelan, A., Feighery, C., Bresnihan, B., Casey, E., Colclough, M., Freyne, P., Murphy, A., McNeill, T. A., Shirodaria, P. V., Price, S., Thompson, J., Fay, A., Roberts, S. D., Frazer, Hilary E., Wisdom, G. B., McCrea, J. D., Boyd, M. W. J., Moriarty, M., and Molony, J.

Published
1984
Full Text
View/download PDF

50. Structural changes in amorphous GexSiOy on the way to nanocrystal formation

Author

Nyrow, A., Sternemann, C., Sahle, C. J., Hohl, A., Zschintzsch-Dias, M., Schwamberger, A., Mende, K., Brinkmann, I., Sala, M. M., Wagner, R., Meier, A., Voelklein, F., and Tolan, M.

Subjects
VISIBLE PHOTOLUMINESCENCE [KeyWords Plus], ALLOY-FILMS, EXCITATIONS, THIN-FILMS, GE NANOCRYSTALS, MEMORY, LUMINESCENCE, DEFECTS, SILICON NANOCRYSTALS, MICROCRYSTALS
Abstract

Temperature induced changes of the local chemical structure of bulk amorphous GexSiOy are studied by Ge K-edge x-ray absorption near-edge spectroscopy and Si L-2/3-edge x-ray Raman scattering spectroscopy. Different processes are revealed which lead to formation of Ge regions embedded in a Si oxide matrix due to different initial structures of as-prepared samples, depending on their Ge/Si/O ratio and temperature treatment, eventually resulting in the occurrence of nanocrystals. Here, disproportionation of GeOx and SiOx regions and/or reduction of Ge oxides by pure Si or by a surrounding Si sub-oxide matrix can be employed to tune the size of Ge nanocrystals along with the chemical composition of the embedding matrix. This is important for the optimization of the electronic and luminescent properties of the material.

Published
2013

Catalog

Books, media, physical & digital resources
See catalog results