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Hedayat H, Bugini D, Karbassi S, Friedmann S, van Wezel J, Clark SR, Sayers C, Da Como E, Cerullo G, Dallera C, Carpene E. Charge-density-wave in 1T-TiSe2: exciton-phonon separation by femtosecond valence band dynamics. EPJ Web Conf 2019. [DOI: 10.1051/epjconf/201920504008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the driving mechanism leading to charge-density-wave transition in 1T-TiSe2 single crystals. Our results show that both exciton instability and phonons cooperate to develop the charge ordered phase below 202 K.
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2
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Bugini D, Boschini F, Hedayat H, Yi H, Chen C, Zhou X, Manzoni C, Dallera C, Cerullo G, Carpene E. Ultrafast spin-polarized electron dynamics in the unoccupied topological surface state of Bi 2Se 3. J Phys Condens Matter 2017; 29:30LT01. [PMID: 28574404 DOI: 10.1088/1361-648x/aa76c0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The three-dimensional topological insulator Bi2Se3 presents two cone-like dispersive topological surface states centered at the [Formula: see text] point. One of them is unoccupied in equilibrium conditions and located 1.8 eV above the other one lying close to the Fermi level. In this work we employ time- and angle-resolved photoemission spectroscopy with circularly polarized pump photons to selectively track the spin dynamics of the empty topological states. We observe that spin-polarized electrons flow along the topological cone and recombine towards the unpolarized bulk states on a timescale of few tens of femtoseconds. This provides direct evidence of the capability to trigger a spin current with circularly polarized light.
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Affiliation(s)
- D Bugini
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milan, 20133, Italy. Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli 70/3, Milan, 20133, Italy
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3
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Boschini F, Hedayat H, Piovera C, Dallera C, Gupta A, Carpene E. A flexible experimental setup for femtosecond time-resolved broad-band ellipsometry and magneto-optics. Rev Sci Instrum 2015; 86:013909. [PMID: 25638099 DOI: 10.1063/1.4906756] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A versatile experimental setup for femtosecond time-resolved ellipsometry and magneto-optical Kerr effect measurements in the visible light range is described. The apparatus is based on the pump-probe technique and combines a broad-band probing beam with an intense near-infrared pump. According to Fresnel scattering matrix formalism, the analysis of the reflected beam at different polarization states of the incident probe light allows one to determine the diagonal and the off-diagonal elements of the dielectric tensor in the investigated sample. Moreover, the pump-probe method permits to study the dynamics of the dielectric response after a short and intense optical excitation. The performance of the experimental apparatus is tested on CrO2 single crystals as a benchmark.
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Affiliation(s)
- F Boschini
- Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - H Hedayat
- Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - C Piovera
- Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - C Dallera
- Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - A Gupta
- Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - E Carpene
- CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
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4
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Boschini F, Hedayat H, Dallera C, Farinello P, Manzoni C, Magrez A, Berger H, Cerullo G, Carpene E. An innovative Yb-based ultrafast deep ultraviolet source for time-resolved photoemission experiments. Rev Sci Instrum 2014; 85:123903. [PMID: 25554305 DOI: 10.1063/1.4903347] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Time- and angle-resolved photoemission spectroscopy is a powerful technique to study ultrafast electronic dynamics in solids. Here, an innovative optical setup based on a 100-kHz Yb laser source is presented. Exploiting non-collinear optical parametric amplification and sum-frequency generation, ultrashort pump (hν = 1.82 eV) and ultraviolet probe (hν = 6.05 eV) pulses are generated. Overall temporal and instrumental energy resolutions of, respectively, 85 fs and 50 meV are obtained. Time- and angle-resolved measurements on BiTeI semiconductor are presented to show the capabilities of the setup.
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Affiliation(s)
- F Boschini
- Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - H Hedayat
- Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - C Dallera
- Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - P Farinello
- Dipartimento di Ingegneria Industriale e dell'Informazione, Università di Pavia, 27100 Pavia, Italy
| | - C Manzoni
- IFN-CNR Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - A Magrez
- Institute of Condensed Matter Physics (ICMP), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - H Berger
- Institute of Condensed Matter Physics (ICMP), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - G Cerullo
- Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
| | - E Carpene
- IFN-CNR Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
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Mazet T, Malterre D, François M, Dallera C, Grioni M, Monaco G. Nonpareil Yb behavior in YbMn6Ge(6-x)Sn(x). Phys Rev Lett 2013; 111:096402. [PMID: 24033054 DOI: 10.1103/physrevlett.111.096402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Indexed: 06/02/2023]
Abstract
We investigate the temperature dependence of the Yb valence in YbMn6Ge1.8Sn4.2 and YbMn6Ge1.6Sn4.4 using resonant inelastic x-ray scattering experiments. Yb is found to be in an intermediate valent state in the whole investigated temperature range (10-450 K). We thus prove that the unusually high magnetic ordering temperature of Yb (∼60 and 90 K for x=4.2 and 4.4, respectively) involves an intermediate valent Yb, an unprecedentedly observed phenomenon. Further, an anomalous increase in the Yb valence is observed upon cooling. A scenario is proposed to explain this unusual behavior. It is based on the presence of magnetically ordered Mn moments and on an Anderson Hamiltonian with a Zeeman term modeling the magnetic interactions.
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Affiliation(s)
- T Mazet
- Institut Jean Lamour, UMR 7198, Université de Lorraine-Boîte Postale 70239, 54506 Vandœuvre-lès-Nancy, France
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Ilakovac V, Brookes NB, Cezar JC, Thakur P, Bisogni V, Dallera C, Ghiringhelli G, Braicovich L, Bernu S, Berger H, Forró L, Akrap A, Hague CF. BaVS3 probed by V L edge x-ray absorption spectroscopy. J Phys Condens Matter 2012; 24:045503. [PMID: 22217443 DOI: 10.1088/0953-8984/24/4/045503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Polarization dependent vanadium L edge x-ray absorption spectra of BaVS(3) single crystals are measured in the four phases of the compound. The difference between signals with the polarizations E perpendicular to c and E is parallel to c (linear dichroism) changes with temperature. Besides increasing the intensity of one of the maxima, a new structure appears in the pre-edge region below the metal-insulator transition. More careful examination brings to light that the changes start already with pretransitional charge density wave fluctuations. Simple symmetry analysis suggests that the effect is related to rearrangements in the E(g) and A(1g) states, and is compatible with the formation of four inequivalent V-sites along the V-S chain.
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Affiliation(s)
- V Ilakovac
- Université Pierre et Marie Curie, CNRS UMR 7614, LCP-MR, Paris, France.
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7
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Carpene E, Mancini E, Dallera C, Ghiringhelli G, Manzoni C, Cerullo G, De Silvestri S. A versatile apparatus for time-resolved photoemission spectroscopy via femtosecond pump-probe experiments. Rev Sci Instrum 2009; 80:055101. [PMID: 19485528 DOI: 10.1063/1.3125049] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A laser-based system for time-resolved photoemission spectroscopy using up to 6.2 eV photons is presented. The versatility of the laser source permits several combinations of pump and probe photon energies with pulse durations of 50-100 fs. The ultrahigh vacuum system, equipped with evaporators, a low energy electron diffraction system and an Auger spectrometer, grants the possibility to grow and characterize thin films in situ. The electron energy analyzer is a time-of-flight spectrometer with a multianode detector allowing high count rates. The performance of the whole experimental setup is investigated on Cu(100), Cu(111), and Ag(111) single crystals.
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Affiliation(s)
- E Carpene
- Dipartimento di Fisica, CNR-INFM Ultras, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy.
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Ghiringhelli G, Piazzalunga A, Dallera C, Schmitt T, Strocov VN, Schlappa J, Patthey L, Wang X, Berger H, Grioni M. Observation of two nondispersive magnetic excitations in NiO by resonant inelastic soft-X-Ray scattering. Phys Rev Lett 2009; 102:027401. [PMID: 19257316 DOI: 10.1103/physrevlett.102.027401] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Indexed: 05/27/2023]
Abstract
We present high resolution (DeltaE=120 meV) resonant inelastic x-ray scattering data measured at the Ni L3 edge (2p_{3/2}-->3d) on the paradigmatic antiferromagnetic oxide NiO. Spectra reveal clear signatures of magnetic excitations at approximately 95 and approximately 190 meV whose energy seems independent from transferred momentum. These spectral features are well reproduced by a single Ni2+ ion model in an effective exchange field. Within this local model the two magnetic excitations are characterized by a variation of the atomic magnetic moment along the local ordering direction (DeltaS_{alpha}) of one and two units. The DeltaS_{alpha}=2 case has different nature from bimagnons observed in optical Raman spectra, for which DeltaS_{alpha}=0.
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Affiliation(s)
- G Ghiringhelli
- CNR-INFM Coherentia and Soft, Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, I-20133 Milano, Italy
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Månsson M, Claesson T, Finazzi M, Dallera C, Brookes NB, Tjernberg O. Using high energy angle resolved photoelectron spectroscopy to reveal the charge density in solids. Phys Rev Lett 2008; 101:226404. [PMID: 19113495 DOI: 10.1103/physrevlett.101.226404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Indexed: 05/27/2023]
Abstract
The charge density in solids is a fundamental parameter. Here we demonstrate that the charge density can be determined by the use of angle resolved photoelectron spectroscopy. The method, which involves a Fourier-like transform from momentum space to real space, is demonstrated by utilizing soft x-ray angle resolved photoelectron spectroscopy to sample the complete three-dimensional Brillouin zone of copper. It is also shown that this can be done in an energy resolved way as to extract the charge density contribution from states of a particular energy.
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Affiliation(s)
- M Månsson
- Materials Physics, Royal Institute of Technology KTH, Electrum 229, S-164 40 Kista, Sweden
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10
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Kotani A, Matsubara M, Uozumi T, Ghiringhelli G, Fracassi F, Dallera C, Tagliaferri A, Brookes N, Braicovich L. Theoretical and experimental study of resonant inelastic X-ray scattering for NiO. Radiat Phys Chem Oxf Engl 1993 2006. [DOI: 10.1016/j.radphyschem.2005.07.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Chiuzbăian SG, Ghiringhelli G, Dallera C, Grioni M, Amann P, Wang X, Braicovich L, Patthey L. Localized electronic excitations in NiO studied with resonant inelastic X-Ray scattering at the Ni M threshold: evidence of spin flip. Phys Rev Lett 2005; 95:197402. [PMID: 16384022 DOI: 10.1103/physrevlett.95.197402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Indexed: 05/05/2023]
Abstract
We studied the neutral electronic excitations of NiO localized at the Ni sites by measuring the resonant inelastic x-ray scattering (RIXS) spectra at the Ni M2,3 edges. The good energy resolution allows an unambiguous identification of several spectral features due to excitations. The dependence of the RIXS spectra on the excitation energy gives evidence of local spin flip and yields a value of 125 +/- 15 meV for the antiferromagnetic exchange interaction. Accurate crystal field parameters are also obtained.
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Affiliation(s)
- S G Chiuzbăian
- Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
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12
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Claesson T, Månsson M, Dallera C, Venturini F, De Nadaï C, Brookes NB, Tjernberg O. Angle resolved photoemission from Nd1.85Ce0.15CuO4 using high energy photons: a fermi surface investigation. Phys Rev Lett 2004; 93:136402. [PMID: 15524743 DOI: 10.1103/physrevlett.93.136402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2003] [Indexed: 05/24/2023]
Abstract
We have performed an angle resolved photoemission study on a single crystal of the optimally electron doped (n-type) cuprate superconductor Nd2-xCexCuO4 (x=0.15) at a photon energy of 400 eV. The Fermi surface is mapped out and is, in agreement with earlier measurements, of hole-type with the expected Luttinger volume. However, comparing with previous low energy measurements, we observe a different Fermi surface shape and a different distribution of spectral intensity around the Fermi surface contour. The observed Fermi surface shape indicates a stronger electron correlation in the bulk as compared to the surface.
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Affiliation(s)
- T Claesson
- Laboratory of Materials and Semiconductor Physics, Royal Institute of Technology, Electrum 229, S-164 40 Kista, Sweden.
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13
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Colarieti-Tosti M, Katsnelson MI, Mattesini M, Simak SI, Ahuja R, Johansson B, Dallera C, Eriksson O. First-principles theory of intermediate-valence f-electron systems. Phys Rev Lett 2004; 93:096403. [PMID: 15447120 DOI: 10.1103/physrevlett.93.096403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Indexed: 05/24/2023]
Abstract
We propose a first-principles based method for calculating the electronic structure and total energy of solids in an intermediate-valence configuration. The method takes into account correlation effects (d-f Coulomb interaction) and many-body renormalization of the effective hybridization parameter of the f system. As an example, the formation of a pressure-induced intermediate-valence state in Yb is considered and its electronic structure and equation of state are calculated and compared to experimental data. The agreement is found to be excellent for both properties, and we argue that the developed method, which applies to any element or compound, provides for the first time a quantitative theoretical treatment of intermediate-valence materials.
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Affiliation(s)
- M Colarieti-Tosti
- Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden
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Ghiringhelli G, Brookes NB, Annese E, Berger H, Dallera C, Grioni M, Perfetti L, Tagliaferri A, Braicovich L. Low energy electronic excitations in the layered cuprates studied by copper L3 resonant inelastic x-ray scattering. Phys Rev Lett 2004; 92:117406. [PMID: 15089169 DOI: 10.1103/physrevlett.92.117406] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2003] [Indexed: 05/24/2023]
Abstract
We have measured the resonant inelastic x-ray scattering (RIXS) spectra at the Cu L3 edge in a variety of cuprates. Exploiting a considerably improved energy resolution (0.8 eV) we recorded significant dependencies on the sample composition and orientation, on the scattering geometry, and on the incident photon polarization. The RIXS final states correspond to two families of electronic excitations, having local (dd excitations) and nonlocal (charge-transfer) character. The dd energy splitting can be estimated with a simple crystal field model. The RIXS at the L3 edge demonstrates here a great potential, thanks to the resonance strength and to the large 2p spin-orbit splitting.
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Affiliation(s)
- G Ghiringhelli
- INFM-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
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15
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Denning RG, Green JC, Hutchings TE, Dallera C, Tagliaferri A, Giarda K, Brookes NB, Braicovich L. Covalency in the uranyl ion: A polarized x-ray spectroscopic study. J Chem Phys 2002. [DOI: 10.1063/1.1510445] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Dallera C, Grioni M, Shukla A, Vankó G, Sarrao JL, Rueff JP, Cox DL. New spectroscopy solves an old puzzle: the Kondo scale in heavy fermions. Phys Rev Lett 2002; 88:196403. [PMID: 12005653 DOI: 10.1103/physrevlett.88.196403] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2001] [Indexed: 05/23/2023]
Abstract
Resonant inelastic x-ray scattering (RIXS) yields clear evidence of spectroscopic Kondo scales in heavy fermions. In YbInCu4 and YbAgCu4 RIXS probes the Yb2+ component of the hybrid ground state and the temperature dependence of the Yb 4f occupation. We report a sudden valence change at a phase transition in YbInCu4, but a continuous temperature dependence in YbAgCu4, consistent with the predictions of the Anderson impurity model, for a Kondo temperature T(K) = 70 K. These results solve a long-standing controversy and establish RIXS as a quantitative probe of the electronic structure of strongly correlated electron systems.
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Affiliation(s)
- C Dallera
- INFM-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
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Dallera C, Puppin E, Trezzi G, Incorvaia N, Fasana A, Braicovich L, Brookes NB, Goedkoop JB. Soft X-ray Emission Spectroscopy at ESRF Beamline 26 Based on a Helical Undulator. J Synchrotron Radiat 1996; 3:231-8. [PMID: 16702684 DOI: 10.1107/s0909049596006061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A new soft X-ray spectrograph for X-ray emission spectroscopy excited by synchrotron radiation is presented. The apparatus is now installed on beamline 26 at the ESRF in Grenoble. A brief description of the beamline is given and then several components of the spectrograph are covered in more detail. Results of experiments performed both with direct non-monochromated undulator radiation and with monochromated radiation are reported.
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Dallera C, Puppin E, Braicovich L, Brookes NB. Electronic states of the theta ' phase in Cu-Al alloys as compared to C16-CuAl2: Cu L alpha emission excited directly by undulator radiation. Phys Rev B Condens Matter 1996; 53:965-968. [PMID: 9983530 DOI: 10.1103/physrevb.53.965] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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