XAS: X-ray Absorption Spectroscopy Hwo-Shuenn Sheu hsheu@nsrrc.org.tw NSRRC, Taiwan Malaya University, 2011/12/14-5 1 outline Basic principles for XAS Experimental setup for XAS Applications 2 1
The X-ray Absorption Coefficient: μ I = I 0 e μt Absorption Photon energy (ev) 3 X-ray Absorption 4 2
Why need SR X-ray sources? 5 XAS accessible elements 26 H Li Na Be Mg XANES only; EXAFS hardish; K-edge EXAFS; L3-edge EXAFS; L3/K-edge EXAFS B Al C Si N P O S F Cl He Ne Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba * Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra * * Lr Rf Db Sg Bh Hs Mt Ds Rg * La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb ** Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No 6 3
X-ray Absorption Basic Principles: x 1.2 0.8 0.4 XANES -20 50eV EXAFS 50 1000eV NEXAFS: near edge x-ray absorption fine stuture XANES: x-ray absorption near edge spectroscopy EXAFS: extended x-ray absorption fine structure 0.0 -Ge 11 11.5 12 Pre-edge X-ray photon energy (kev) 7 X-ray absorption spectroscopy 8 4
The interference of the outgoing and backscattered photoelectron wave 1.2 0.8 0.4 0.0 11 11.5 12 9 10 From Matthew Newville 5
11 From Matthew Newville 12 From Matthew Newville 6
Excursion: Wave-particle dualism 13 The EXAFS formula: quantitative information 14 7
15 From Matthew Newville Structure parameters extracted from EXAFS R N Z 16 8
Experimental setup for XAS Transmission mode I0 x ln I t Fluorescence mode x = I f / I 0 17 XAS Beamline (BL17C1) at NSRRC I 0 I t sample I ref Dr. Jyh Fu Lee 18 9
Fluorescent (Lytle & 13 element array) detector 19 Transmission mode (a) and fluorescent mode (b) 20 10
Applications 21 22 11
K-shell photoabsorption of N 2 molecule C.T. Chen and F. Sette, Phys. Rev. A 40 (1989) (a) * (c) N 1s 1 g K-shell photoabsorption of gas-phase N 2 Absorption Intensity (arb.units) * N 1s 1 g N 1s Rydberg series x10 Double excitations Shape resonance 400 405 410 415 420 Photon energy (ev) Absorption Intensity (arb. Units) 400 401 402 (b) 1 2 3 4 Double excitations 414 415 N 1s Rydberg series 5 406 407 408 409 410 Photon Energy (ev) 6 7 8 9 10 11 12 13 3 (a) 8 vibrational levels observed in the absorpttion spectrum: N 1s 1 * g (b) N 1s Rydberg series (c) Double excitations in the N 2 spectrum Rydberg associated to the N 1s 1 * g transition. 23 XANES Chemical information: oxidation state 1 0.5 Cu 2 O Cu CuO KCuO 2 Y-Ba-Cu-O Oxidation Numbers (formal valences) I Cu 2 O II CuO III KCuO 2 Higher transitions energy are expected for higher valence states. 0 8970 8990 E (ev) (J.B. Boyce et al. Phys. Rev. B 1987) 24 12
Pt L 3 and L 2 edge XANES 25 White line reflects the d-orbital occupancy 26 13
White line reflects oxidation state Higher oxidation state More empty d-orbitals More intense white line 27 Pre edge reflect local coordination symmetry Co K-edge Td (tetrahedral) (tetrahedral) (spinel) (octahedral) (octahedral) Oh 28 14
EXAFS of LiCoO 2 powder 29 EXAFS of LiCoO 2 powder 30 15
EXAFS of LiCoO 2 powder 31 EXAFS of LiCoO 2 during charging cycled Static ordering Thermal vibration 32 16
Use EXAFS to probe coordination environment: Na(Co 0.99 Mn 0.01 )O 2 Similar EXAFS spectrum indicate Mn and Co are in similar chemical environment. 33 Ru/Cu core shell structure characterization Ru/SiO 2 Ru-Cu/SiO 2 34 17
Ru/Cu core shell structure characterization Cu/SiO 2 Cu-Ru/SiO 2 35 Ru/Cu core shell structure characterization Ru Cu Fresh Oxidized Fresh Oxidized 36 18
High pressure x-ray absorption spectroscopy 37 Pressure-induced structural distortion of TbMnO3: A combined XRD and XAS study XRD data and the enhanced intensity of the white line and the shifted absorption threshold of Mn K- edge spectra enabled observation of a reduced local Jahn-Teller distortion of Mn sites within MnO 6 octahedra in TbMnO 3 with increasing pressure. These provide spectral evidence for pressureinduced bandwidth broadening for mangnites. Physical Review B 79, 165110 2009 145.7 º Mn(1) b Mn(2) 1.889Å a Mn(2) J` 2.243Å 38 J Mn(1) 19
Horse tail hair has been measured to grow between 390 and 1260 micrometers per day (compared to ca. 330 micrometers for human head hair).[7] The growth of mane hair may be within this range, in which case a 500 micrometer segment would correspond to between approximately 10 30 hours of growth. 39 Determination of Arsenic Poisoning and Metabolism in Hair by Synchrotron Radiation: The Case of Phar Lap** Ivan M. Kempson* and Dermot A. Henry Angew. Chem. Int. Ed. 2010, 49, 4237 4240 40 20
Photo-Induced Magnetization in Co-Fe Prussian Blue Magnets K x Co y [Fe(CN) 6 ] zh 2 O Fe Co C N K + is interstitial Defect (missing Fe) Structural disorder dictated by composition/processing PIM initially observed in K 0.2 Co 1.4 [Fe(CN) 6 ] 6.9H 2 O O.Sato et al., Science 272, 704 (1996) - Ferrimagnetic ordering below ~16 K - Magnetization increase obtained by red light - Photoinduced state has lifetime >10 5 s at low T - Effect reversed by blue light, heating 41 Magnetization Change (x 10 5 emu-g) 10 5 0-5 Rb j Co k [Fe(CN) 6 ] l.nh 2 O Light Off Magnetic field parallel Magnetic field perpendicular x5 Light On -10-10 0 10 20 30 40 50 Time (min) The magnetism of a nanoscale film of a molecule-based magnet is controlled by both light and orientation. h Diamagnetic Fe II -CN-Co III Electron transfer and spin crossover Ferrimagnetic Fe III -CN-Co II Photoinduced magnetism in Rb j Co k [Fe(CN) 6 ] l.nh 2 O 42 21
XRD and XANES of K x Co y [Fe(CN) 6 ] Synthesized in Various Concentration of KCl (2 0 0) reflection XANES of Co K-edge 4 2.0x10 4 1.0 M KCl 3 Counts (a. u.) 1.5x10 4 1.0x10 4 5.0x10 3 0.5 M KCl 0.1 M KCl 0 M KCl Absorption (a.u.) 2 1 0M KCl 0.1M KCl 0.5M KCl 1M KCl 0 0.0 14.0 14.2 14.4 14.6 14.8 15.0 15.2 15.4 15.6 15.8 16.0 2 (degree) 7700 7710 7720 7730 7740 7750 7760 7770 7780 Energy (ev) 43 X-ray Powder Diffraction of K x Co y [Fe(CN) 6 ] Synthesized in 0.1 M KCl Solution counts (a. u.) 12000 10000 8000 6000 4000 2000 Space group: F m 3 m PI : a=10.2787(1) PII : a= 9.9851(6) wrp=0.050 Rp=0.033 X=0.8529 5/13/00 Co N C Fe PI : 1.987(5) 1.140 2.012(5) PII: 1.86(3) 1.140 1.996(3) 0-2000 10 20 30 40 50 60 70 80 90 2 (degree) 44 22
Water- desorption of K x Co y [Fe(CN) 6 ].nh 2 O XANES of Co K-edge Heating vacuum Absorption 2.5 2.0 1.5 1.0 25 C 45 C 55 C 65 C 75 C 85 C 95 C 105 C 125 C Co K-edge 2.0 0.5 10-3 torr (30min) 7700 7710 7720 7730 7740 7750 Absorption (a. u.) 1.5 1.0 0.5 Pre-edge RT in air 14K to RT in Vacuum 14K to RT then in air Absorption 1.0 0.9 0.8 0.7 0.6 7% 11% 18% 19% 32% 42% Energy (ev) 0.5 0.0 7700 7710 7720 7730 7740 7750 7760 Energy (ev) 0.4 0.3 7700 7710 7720 7730 7740 7750 7760 Energy (ev) Humidity 45 Light irradiation of Co, Fe Prussian Blue magnets Lytle Detector APD Cryostat Xe Lamp 46 23
0.180 0.175 0.170 0.165 7129.0 7129.5 7130.0 7130.5 7131.0 7131.5 7132.0 7132.5 7133.0 0.160 XANES of Co K-edge: In-situ Xe-lamp Red light (650±40nm) illuminated at 15K Absorption 0.8 0.7 0.6 0.5 0.4 0.3 Co-Kedge 30 min 27 min 20 min 11 min 4.5 min 1 min 0 min The Co 3+ become Co 2+ during red light illumination at 15K and saturation in 20 min. The K-edge of Fe also show significant change during the irradiation. 0.20 Fe K-edge 0.15 0.2 0.10 0.1 7700 7710 7720 7730 7740 7750 7760 Energy (ev) 0.05 0 min 38 min 42 min 0.00 45 min 7100 7110 7120 7130 7140 7150 47 X-ray Absorption Spectroscopic Studies on Light-Induced Excited Spin State Trapping of an Fe(II) Complex Yu Wang, et al J. Am. Chem. Soc. 2000, 122(24), 5742-5747 48 24
X-ray Absorption Spectroscopic Studies on Light-Induced Excited Spin State Trapping of an Fe(II) Complex K-edge L-edge 49 X-ray Absorption Spectroscopic Studies on Light-Induced Excited Spin State Trapping of an Fe(II) Complex 50 25
X-ray Absorption Spectroscopic Studies on Light-Induced Excited Spin State Trapping of an Fe(II) Complex 51 Acknowledgement Prof. Yu Wang ( NTU) Prof. Bing-Joe Hwang (NTUST) Dr. Jyh-Fu Lee (NSRRC) Dr. Ting-Shan Chan (NSRRC) Dr. Jin-Ming Chen (NSRRC) Thank you for your attention! 52 26