| 1. |
- Shi, X., et al.
(författare)
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Quantitative assessment of structural and compositional colors induced by femtosecond laser : A case study on 301LN stainless steel surface
- 2019
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Ingår i: Applied Surface Science. - : Elsevier B.V.. - 0169-4332 .- 1873-5584. ; 484, s. 655-662
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Tidskriftsartikel (refereegranskat)abstract
- The topic of durable coloration and passivation of metal surfaces using state-of-the-art techniques has gained enormous attention and devotion with unremitting efforts of researchers worldwide. Although femtosecond laser marking has been performed on many metals, the related coloration mechanisms are mainly referred to structural colors produced by the interaction of visible light with periodic surface structures. Yet, general quantitative determination of the resulting colors and their origins remain elusive. In this work, we realized quantitative separations of structural colors and compositional pigmentary colors on 301LN austenitic stainless steel surfaces that were treated by femtosecond laser machining. The overall color information was extracted from surface reflectance, with structural color given by numerical simulations, and oxide compositions by chemical state analysis. It was shown that the laser-induced apparent colors of 301LN steel surfaces were combinations of structural and compositional colorations, with the former dominating the angular response and the latter setting up the brownish bases. In addition to the quantification of colors, the analysis method in this work may be useful for the generation and specification of tailored color palettes for practical coloration on metal surfaces by femtosecond laser marking.
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| 2. |
- Andersson, T., et al.
(författare)
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Electronic structure transformation in small bare Au clusters as seen by x-ray photoelectron spectroscopy
- 2017
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:1
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Tidskriftsartikel (refereegranskat)abstract
- Free bare gold clusters in the size range from few tens to few hundred atoms (<= 1 nm dimensions) have been produced in a beam, and the size-dependent development of their full valence band including the 5d and 6s parts has been mapped 'on the fly' by synchrotron-based photoelectron spectroscopy. The Au 4f core level has been also probed, and the cluster-specific Au 4f ionization energies have been used to estimate the cluster size. The recorded in the present work valence spectra of the small clusters are compared with the spectra of the large clusters (N similar to 10(3)) created by us using a magnetron-based gas aggregation source. The comparison shows a substantially narrower 5d valence band and the decrease in its splitting for gold clusters in the size range of few hundred atoms and below. Our DFT calculations involving the pseudopotential method show that the 5d band width of the ground state increases with the cluster size and by the size N = 20 becomes comparable with the experimental width of the valence photoelectron spectrum. Similar to the earlier observations on supported clusters we interpret our experimental and theoretical results as due to the undercoordination of a large fraction of atoms in the clusters with N similar to 10(2) and below. The consequences of such electronic structure of small gold clusters are discussed in connection with their specific physical and chemical properties related to nanoplasmonics and nanocatalysis.
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| 3. |
- Ceolin, D., et al.
(författare)
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Auger resonant-Raman study at the Ar K edge as probe of electronic-state-lifetime interferences
- 2015
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 91:2
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Tidskriftsartikel (refereegranskat)abstract
- The resonant-Auger decay in argon following Ar 1s - np excitations was studied under resonant-Raman conditions, i.e., with a total instrumental bandwidth much narrower than the natural linewidth of the absorption features. These state-of-the-art experiments are combined with a radiationless resonant-Raman scattering theory. The main results include identification of the energy position of some high-lying Rydberg states previously masked by insufficient resolution and clear evidence of electronic-state-lifetime interference phenomena.
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| 4. |
- Hautala, Lauri, et al.
(författare)
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Experimental observation of structural phase transition in CsBr clusters
- 2017
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Ingår i: Physical Review B. - 1098-0121. ; 95:4
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Tidskriftsartikel (refereegranskat)abstract
- Formation and growth of CsBr clusters embedded in unsupported Ar clusters was studied using synchrotron radiation photoelectron spectroscopy. The development of the core-level electronic structure for cluster sizes between a few and a few hundred atoms contained information about the local coordination of the constituent particles. The experimental results indicate that a gradual structural phase transition from NaCl structure to CsCl structure for CsBr clusters takes place at around 160 atoms per cluster.
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| 5. |
- Piancastelli, Maria Novella, et al.
(författare)
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X-ray versus Auger emission following Xe 1s photoionization
- 2017
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 95:6
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Tidskriftsartikel (refereegranskat)abstract
- Xe 1s photoelectron spectra were measured at SPring-8, Japan. The core-hole lifetime broadening was found to be 9.6 eV, yielding a lifetime of similar to 68 as. The amount of radiative versus nonradiative decay was assessed by recording Auger LMM spectra below and above the K edge. Below the K edge, L vacancies are produced only by direct photoionization, while above the K edge some of these vacancies are mainly produced by KL emission following 1s photoionization. Due to the dipole selection rule for x-ray emission, the dominant role of the KL relaxation process is rather directly observed.
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