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21.
22.
We consider the archetypal frustrated antiferromagnet SrCr(9p)Ga(12-9p)O?? in its well-known spin-liquid state, and demonstrate that a Cr(3+) spin S=3/2 ion in direct proximity to a pair of vacancies (in disordered p<1 samples) is cloaked by a spatially extended spin texture that encodes the correlations of the parent spin liquid. In this spin-liquid regime, our analytic theory predicts that the combined object has a magnetic response identical to a classical spin of length S/2=3/4, which dominates over the small intrinsic susceptibility of the pure system. This fractional-spin texture leaves an unmistakable imprint on the measured ?1Ga nuclear magnetic resonance line shapes, which we compute using Monte Carlo simulations and compare with experimental data. 相似文献
23.
M. Mohapatra Y.P. NaikV. Natarajan T.K. SeshagiriS.V. Godbole 《Physica B: Condensed Matter》2011,406(10):1977-1982
Lithium titanate ceramics doped with Eu were synthesized and their photoluminescence (PL) and emission spectral characteristics were investigated. PL spectra of the sample showed peaks corresponding to the 5D0→7FJ (J=0, 1, 2, 3 and 4) transitions under 230 nm excitation. The fluorescence lifetimes of Eu3+ ions were found out to be 645 μs. Strong red emission coming from the hypersensitive 5D0→7F2 transition of Eu3+ ion suggested the presence of the dopant ion in highly asymmetric environment. Further analysis of the emission spectrum revealed that the symmetry of the metal ion is very low i.e. C2. The emission intensity of the sample was compared with a commercial phosphor to get an idea about the commercial utility of the phosphor. Various emission properties for the system namely Judd-Ofelt intensity parameters, spontaneous emission probabilities, branching ratios, radiative lifetimes and quantum efficiency were evaluated for the dopant ion by adopting standard procedure. 相似文献
24.
25.
A. Sengupta M. J. Kulkarni S. V. Godbole 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):961-965
DHOA (Di-n-hexyl-octanamide) is one of the alternative extractants to TBP (tri-n-butyl phosphate) known for the extraction of uranium from moderate nitric acid medium without significant extraction of the fission products. Analytical application of DHOA was explored to develop a methodology for determination of trace metallic constituents in uranium based nuclear materials. This involved the separation of uranium matrix by 1.1 M DHOA-dodecane followed by the analysis of the raffinate for trace constituents by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). A systematic study showed that four contacts of 1.1 M DHOA-dodecane were required for quantitative extraction of U from 4 M HNO3 feed for the sample size of 1 g in 10 mL. The feasibility of using DHOA for extraction of U from trace metallic constituents in U based fuel materials without losing trace quantities of analytes of interest was studied by using synthetic samples after appropriate spiking of common impurities and critical elements at their required specification limits (common elements—5 ppm, critical elements—1 ppm). A systematic study was carried out to compare the analytical performance of DHOA with TBP, which revealed that DHOA could successfully be employed for the determination of 19 trace constituents with lower estimation limits of 5 ppm for common impurities and 1 ppm for critical elements. 相似文献
26.
Extensive studies have been carried out on the optical conversion of F and F-aggregate colour centres produced in lithium
fluoride single crystal on gamma irradiation. Using 308 nm XeCl laser it has been shown that significantly large population
build-up of F
3
+
centre and reduction in the population of undesirable F2 centres can be achieved in gamma irradiated crystal at room temperature due to multistep photoionization processes. These
and other investigations have provided a scheme for possible laser action based on F
3
+
colour centres in LiF crystal at room temperature. 相似文献
27.
28.
Jahar L. Mukherjee Chandra P. Khattak Kedar P. Gupta Franklin F.Y. Wang 《Journal of solid state chemistry》1978,24(2):163-167
Ba2NaNb5O15 (BSN) exhibits a large thermal contraction in its c-axis between 350° and 750°C. This behaviour contributes to a serious cracking problem during its crystal growth. The substitutions of Gd for Ba and/or Na in BSN can be made with either anion or cation compensation. The former, namely, type A, compositions were found to eliminate the thermal contraction behaviors, and had small variations in their linear thermal expansion coefficients, α, between 50° and 650°C. With good ferroelectric and dielectric properties, they showed potentials to replace the BSN crystal in electro-optic devices. 相似文献
29.
Summary Thermal decomposition of manganese(II) soaps of general composition, Mn(O2CR)2 (where R = C17H33, C11H23, C9H19, C7H15) has been studied by t.g.a. and a probable mechanism of decomposition is proposed. The activation energies have been determined using the different equations of Horowitz and Metzger and of Coats and Redfern. The results obtained are consistent. 相似文献
30.
A.G. Page S.V. Godbole K.H. Madraswala Madhuri J. Kulkarni Vanita S. Mallapurkar B.D. Joshi 《Spectrochimica Acta Part B: Atomic Spectroscopy》1984,39(4):551-557
Feasibility studies have been carried out on the use of a graphite electrode assembly for the introduction of U3O8 solid samples into a continuously running low-powered argon inductively coupled plasma for the assay of trace metallic elements in uranium. The d.c. arc carrier distillation procedure has been adopted here for the selective volatilisation of analyte elements from the refractory matrix by injecting analyte vapours into the central zone of the plasma using Scribner-Mullin electrodes covered with a graphite lid having a central opening. The experimental parameters have been optimised for the direct determination of B, Be, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Na, Ni and Pb in U3O8 powders. The analytical performance of the method has been checked by analysing spiked U3O8 samples and is seen to be comparable to or better than d.c. arc methods for these analytes. These results indicate that the carrier-distillation-ICP combination shows promise as a sensitive and precise method for analysis of trace metallic elements in a refractory matrix with a complex spectrum. 相似文献