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排序方式: 共有80条查询结果,搜索用时 265 毫秒
41.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(18):5078-5082
An extremely rare non‐Kramers holmium(III) single‐ion magnet (SIM) is reported to be stabilized in the pentagonal‐bipyramidal geometry by a phosphine oxide with a high energy barrier of 237(4) cm−1. The suppression of the quantum tunneling of magnetization (QTM) at zero field and the hyperfine structures originating from field‐induced QTMs can be observed even from the field‐dependent alternating‐current magnetic susceptibility in addition to single‐crystal hysteresis loops. These dramatic dynamics were attributed to the combination of the favorable crystal‐field environment and the hyperfine interactions arising from 165Ho (I =7/2) with a natural abundance of 100 %. 相似文献
42.
Basudeb Karmakar 《Journal of solid state chemistry》2005,178(9):2663-2672
Infrared reflection spectroscopic (IRRS), ultraviolet-visible-near infrared (UV-Vis-NIR) absorption and photoluminescence upconversion properties with special emphasis on the spectrochemistry of the oxyfluorophosphate (oxide incorporated fluorophosphates) glasses of the Ba(PO3)2-AlF3-CaF2-SrF2-MgF2-Ho2O3 system have been studied with different concentrations (0.1, 0.3 and 1.0 mol%) of Ho2O3. IRRS spectral band position and intensity of Ho3+ ion doped oxyfluorophosphate glasses have been discussed in terms of reduced mass and force constant. UV-Vis-NIR absorption band position has been justified with quantitative calculation of nephelauxetic parameter and covalent bonding characteristics of the host. NIR to visible upconversion has been investigated by exciting at 892 nm at room temperature. Three upconverted bands originated from the 5F3→5I8, (5S2, 5F4)→5I8 and 5F5→5I8 transitions have found to be centered at 491 nm (blue, medium), 543 nm (green, very strong) and 658 nm (red, weak), respectively. These bands have been justified from the evaluation of the absorption, normal (down conversion) fluorescence and excitation spectra. The upconversion processes have been explained by the excited state absorption (ESA), energy transfer (ET) and cross relaxation (CR) mechanisms involving population of the metastable (storage) energy levels by multiphonon deexcitation effect. It is evident from the IRRS study that the upconversion phenomena are expedited by the low multiphonon relaxation rate in oxyfluorophosphate glasses owing to their high intense low phonon energy (∼600 cm−1) which is very close to that of fluoride glasses (500-600 cm−1). 相似文献
43.
M.J. Dick 《Journal of Molecular Spectroscopy》2004,227(2):187-194
Several new transitions of holmium monochloride (HoCl) have been studied at high resolution using laser excitation spectroscopy. Two main transitions, B[17.7]8-X8 and C[19.3]9-X8 have been observed and five bands, 0-0, 0-1, 1-0, 1-1, and 2-1 of the B-X transition and three bands, 0-0, 0-1, and 0-3 of the C-X transition have been obtained at high resolution and rotationally analyzed. Among several low lying states observed in dispersed fluorescence was a strong transition from the C state to a state ∼2140 cm−1 above the ground state. Excitation spectra of this transition have shown that there are apparently two states, ∼6 cm−1 apart. Comparison with ligand field theory calculations are consistent with assigning these states to the excited low lying Ho+(4f116s)Cl− configuration. Several other low lying electronic states have been observed in dispersed fluorescence spectra. Although their assignments could not be established, their energies suggest that they are from the Ho+(4f106s2)Cl− or Ho+(4f116s)Cl− configurations. Rotational constants have been obtained for the B[17.7]8 and C[19.3]9 states and have been used to speculate on the possible electron configurations for these states. 相似文献
44.
Mir Irfanullah 《Journal of luminescence》2010,130(11):1983-101
The photoluminescence properties of three Tb(III) complexes of the form [Tb2(fod)6(μ-bpm)], [Tb(fod)3(phen)] and [Tb(fod)3(bpy)] and optical absorption properties of their Ho(III) analogues (fod=anion of 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, bpm=2,2′-bipyrimidine, phen=1,10-phenanthroline and bpy=2,2′-bipyridyl) in a series of solvents are presented. The luminescence of the complexes is sensitive to changes in environment (ligand/solvent) around Tb(III) and co-sensitization of the ancillary ligands. The enhancement of the luminescence intensity in coordinating solvents is attributed to the transformation of eight-coordination into less symmetric nine-coordination structure around Tb(III). Among phen and bpy, the phen is better co-sensitizer while bpm has been observed as poor co-sensitizer. The enhancement of the oscillator strength of 5G6←5I8 hypersensitive transition in the 4f-4f absorption in some coordinating solvents is attributed to decrease in the symmetry of the field around Ho(III) ion. The [Ho(fod)3(phen)] is inert towards the solvents and retains its bulk structure and composition in solution. The transformation of the holmium complexes in DMSO into [Ho(fod)3(DMSO)2] species is found. The results reveal that the luminescence and 4f-4f absorption properties of lanthanide complexes in solution can be modulated by tuning the coordination structure through ancillary ligands and donor solvents. 相似文献
45.
稀土元素原子发射光谱及其谱线干扰的高分辨率ICP-AES研究——Ⅵ.镧、铽、钬、铒基体对其他稀土元素的光谱干扰 总被引:3,自引:0,他引:3
利用光栅刻线为3600条/mm的高分辨率时序扫描式ICP-AES光谱仪研究镧(La)、铽(Tb)、钬(Ho)、铒(Er)基体分别对其他14个稀土元素共65条“首选分析线”的光谱干扰情况,获得了相应的光谱干扰轮廓和稀土光谱干扰信息,为选择在该4种稀土基体中的其他稀土元素ICP-AES最佳分析线提供了参考。 相似文献
46.
47.
Holmium(III)-doped carbon nanodots (HoBCDs) were synthesized for the first time via hydrothermal treatment of citrate acid (CA), branched-polyethylenimine (BPEI) and diethylenetriamine pentaacetic acid hydrate holmium(III) dihydrogen salt (Ho-DTPA), and their dual-modality bioimaging applications were demonstrated by the use of HeLa cells. The as-prepared nanoprobes exhibited bright fluorescence with an absolute quantum yield of 8% and apparent contrast enhancement in T1-weighted images. 相似文献
48.
Crystal Structure of Tris(m—nitrobenzoato)Samarium Dihydrate 总被引:1,自引:0,他引:1
CrystalStructureofTris(m-nitrobenzoato)SamariumDihydrateMaJian-Fang;JinZhong-Sheng;NiJia-Zuan(LaboratoryofRareEarthChemistrya... 相似文献
49.
In separating yttrium earth mixtures in the range of Dy-Ho-Y-Er the effective partition coefficients were investigated on variation of the molarity of HNO3, the input of rare earth mixture and the composition of the oxide. Based on these studies optimum conditions were selected to prepare the oxides of dysprosium and holmium by the method ofCraig-distribution. 相似文献
50.
《Journal of chromatography. A》2003,990(1-2):311
The method of capillary isotachophoresis with conductivity detection was applied for the determination of the physico-chemical characteristics (conditional stability constants log β′) of holmium and yttrium complexes with DTPA (diethylenetriaminepentaacetic acid) and DOTA (1,4,7,10-tetraazadodecane-N,N′,N″,N-tetraacetic acid). The log β′ determination is based on the linear relation between the stability constants of lanthanide–DTPA (lanthanide–DOTA) complexes and the reduction of the zone of the complex owing to the bleeding phenomena (liberating free metal ion). The stability constants calculated using this relationship are comparable with the literary data obtained by other methods for both holmium (log β′Ho–DTPA=21.9, log β′Ho–DOTA=24.5) and yttrium complexes (log β′Y–DTPA=21.2, log β′Y–DOTA=24.4). Capillary isotachophoresis was applied for the determination of the optimum composition of the reaction mixture (metal:ligand ratio) as well. 相似文献