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41.
P. S. Kulkarni S. D. Sahasrabudhe B. D. Tilak 《Journal of mass spectrometry : JMS》1987,22(10):655-659
The mass spectral fragmentation modes of a variety of substituted 3,4-dihydro-1,3,2-oxazaphosphorin-2-oxides have been investigated. The ionic cycloreversions occur by two competing stepwise heterolytic cleavages, α and β to the phosphorus atom, producing heterodiene and heteropolarophile iminophosphorane ions. Substituents strongly influence the competitive fragmentation modes. Formation of heterodiene ion by retro-Diels–Alder decomposition is preceded by hidden 1,3-hydrogen shift and is the predominant proces in the metastable time region. Further fragmentation of the heterodiene ion occurs by electrophilic substitution-elimination of the hydrogen atom. 相似文献
42.
M.S. Sahasrabudhe S.K. Date S.D. Kulkarni R.N. Bathe 《Solid State Communications》2006,137(11):595-600
The modifications in electrical and magnetic properties of polycrystalline bulk La0.7Ca0.3Mn1−xTxO3 (T=Fe, Ga) samples at relatively higher doping concentration (x=0.08-0.12) are investigated. All the synthesized, single phase samples were subjected to resistivity measurements in the temperature range 50-300 K. No insulator-metal transition (TP) was observed for Fe doped samples with x=0.12. For all the other samples the transition temperature decreased with increase in doping concentration. The small polaron hoping energy was found to increase, rather slowly, with increase in doping concentration. The effect on magnetic properties is also prominently observed with respect to doping element and doping concentration. Interestingly, with the increase in doping concentration, the Curie temperature (TC) and TP separate out significantly indicating decoupling of electric and magnetic properties. Changes in these properties have been analyzed on the basis of magnetic disorder introduced in the system due to the magnetic and nonmagnetic nature of these ions rather than strong lattice effects which is insignificant due to similar ionic radii of Fe+3 and Ga+3 when compared to that of Mn+3. 相似文献
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Vikas Sahasrabudhe 《Solid State Communications》1983,46(9):697-703
For CuxZn1-xFe2O4 spinel ferrites (x = 0.2, 0.4, 0.6 and 0.8), EXAFS of Cu and Fe K-absorption edges have been studied employing LSS theory. With change in copper content, in the spinel system, the basic dependence of cation distribution on degree of inversion has been reported by plotting variation of bond distance “d” with EXAFS parameter ‘α’. This is further substantiated by plotting chemical shifts (ΔE) with EXAFS parameter ‘α’. The necessity of the determination of final state wavefunction for the knowledge of distribution of charge is stressed. 相似文献