日本物理学会 第58回年次大会 2003年3月28日 東北大学(仙台) 28aYE-5 Cuエチレンジアミン錯体 における光誘起相転移の XAFS 横山利彦1 高橋一志2 佐藤治2 1 分子科学研究所 2 神奈川科学技術アカデミー

Transcription

1 u XAFS

2 Previous XAFS works on photoinduced phases Local structures of the photo-induced phases are usually equivalent to the high-temperature ones. Fe (II) (pic) l H OH H. Oyanagi et al., to be published. a. ofe() T. Yokoyama, O. Sato, K. Hashimoto et al., Phys. Rev. B (999) 9. RbMnFe() T. Yokoyama, H. Tokoro, S. Ohkoshi, K. Hashimoto et al., Phys. Rev. B (). o(dtbsq)(dtbat)(phen). H H T. Yokoyama, S. Hayami, O. Sato et al., hem. Phys. Lett. (). Photo-induced phase transition in u (II) (dieten) X dieten =,-diethylethylenediamine ; X = BF, lo Thermochromic transition I. Grenthe et al., Inorg. hem. (99). B. arayanan and M. M. Bhardbharde, J. oord. hem. (99). phase u Planar u (i) Tc = 9 K BF K lo Tetrahedrally distorted u () Photochromic transition K. Takahashi, R. akajima, Z. -Z. Gu, H. Yoshiki, A. Fujishima and O. Sato, hem. ommun. (). Photoinduced (PI) phase transition induced by UV irradiation Powder XRD in PI phase different from the HT one u

3 u K-edge XAFS measurements of u(dieten) X Photoinduced (PI) phase KEK-PF BL9A Si() K Fluorescence yield with Lytle detector Sample thickness should be thin enough for the UV light to penetrate. This requires the fluorescence-yield mode. Hg Lamp - nm ~ mw/cm Quartz window Lytle detector u block K Sample Al foil Kapton window Fluorescence x rays High-temperature (HT) and Low-temperature () phases Inc. x rays After ~ min. UV irradiation, measure in dark KEK-PF BL Si() Transmission HT BF salt K, lo salt K K

4 Absorption (arb. units).... u(dieten) X u K-edge XAES X=BF s pπ HT PI Photon Energy (ev) HT & PI transmission fluorescence X=lO transmission fluorescence Absorption (arb. units)..... stronger pπ transition weaker pπ transition X=BF X=lO s s d pπ HT PI Photon Energy (ev) Planar u Tetrahedrally distorted u

5 Absorption oefficient (arb. units). Kosugi, T. Yokoyama, K. Asakura and H. Kuroda, hem. Phys. 9 (9) 9. s pπ s d polycrystalline samples (creat) [ul ] (D h ) (Et ) [ul ] (D d ) ul H O (D h ) Photon Energy (ev) ul Planar Tetrahedrally distorted planar ul tetrahedrally distorted ul pπ transition stronger weaker Absorption oefficient (arb. units) Polarized XAES of single crystalline (creat) [ul ] s pπ l // z Relative Photon Energy (ev) z polycrystalline l u Z l l

6 EXAFS function k χ(k) (arb. units) Fourier transform - - u(dieten) X HT irrad. u- Wave umber k (Å ) u- u(dieten) X HT irrad. X=BF X=lO X=BF X=lO phase u u Distance R (Å)

7 . nd.. u- EXAFS function k χ(k) (arb. units) phase PI phase Exptl. model HT model Exptl. model HT model Exptl. model HT model Wave umber k (Å - ) X=BF X=lO X=BF X=lO X=BF X=lO

8 phase i 9 Planar u. X-ray BF lo u-,.. u-,.. } u- u-, } u-,.9.9 u-,.. u-() u-,.. u-,.9. u-() u-,.. u-o/f.. heat UV EXAFS BF lo u-.().() (=) u-().().() (=) u-().().() (=) Reconstruction of ethyl group and anions 9 PI phase 9? Ethyl group: cis.9 ~. (?) Distorted Tetrahedral u X-ray lo u-,. u- u-,. u-,.9 u-,. } u-() u-,.9 } u-,9. u-() u-,. u-,.9 u-o.9,. EXAFS BF u-.() (=) u-().() (=) u-().9() (=) EXAFS lo u-.() (=) u-().() (=) u-().9() (=) EXAFS BF u-.() (=) u-().9() (=) u-().() (=) EXAFS lo u-.() (=) u-().9() (=) u-().() (=) Less reconstruction of ethyl group and anions }

9 Photoinduced state of u(dieten) X prepared by Hg-lamp irradiation at K was studied by u K-edge XAFS measurements. XAES: us pπ u tetrahedrally distorted as in EXAFS: nd- u- shell configuration of atoms close to the phase Model structure proposed Distorted Tetrahedral u Reconstruction of ethyl group and anions Planar u Distorted Tetrahedral u Less reconstruction of ethyl group or anions s? 9 heat 9 9 UV phase PI phase T. Yokoyama, K. Takahashi and O. Sato, Phys. Rev. B ().