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Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm−1 region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined.
We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed
in these distances is an indication of the substitution effect.
It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the
case of o-disubstituted benzenes it is only 80% of the para-substituted shift. 相似文献
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With the advent of medium and large gamma detector arrays, it is now possible to look at nuclear structure at high rotational
forces. The role of pairing correlations and their eventual breakdown, along with the shell effects have showed us the interesting
physics for nuclei at high spins — superdeformation, shape co-existence, yrast traps, alignments and their dramatic effects
on nuclear structure and so on. Nuclear structure studies have recently become even more exciting, due to efforts and possibilities
to reach nuclei far off from the stability valley. Coupling of gamma ray arrays with ‘filters’, like neutron wall, charged
particle detector array, gamma ray total energy and multiplicity castles, conversion electron spectrometers etc gives a great
handle to study nuclei produced online with ‘low’ cross-sections. Recently we studied, nuclei in mass region 80 using an array
of 8 germanium detectors in conjunction with the recoil mass analyser, HIRA at the Nuclear Science Centre and, most unexpectedly
came across the phenomenon of identical bands, with two quasi-particle difference. The discovery of magnetic rotation is another
highlight. Our study of light In nucleus, 107In brought us face to face with the ‘dipole’ bands. I plan to discuss some of
these aspects. There is also an immensely important development — that of the ‘radioactive ion beams’. The availability of
RIB, will probably very dramatically influence our ‘conventional’ concept of nuclear structure. The exotic shapes of these
exotic nuclei and some of their expected properties will also be touched upon. 相似文献
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O. A. Anisimov V. N. Verkhovlyuk S. B. Zikirin A. G. Matveeva S. I. Trashkeev Yu. N. Molin 《Applied magnetic resonance》2014,45(9):881-892
A new version of the optically detected electron spin resonance (OD ESR) technique using vacuum ultraviolet radiation to generate radical ion pairs is discussed. The technique can be used to study the spin-correlated processes of charge recombination in thin films that can be useful in spintronics. Distinctive features of photoionization and high-energy (including X-ray) ionization are discussed. The first results obtained by the technique in the study of charge recombination in polymeric and liquid crystal films are presented. The results of the concurrent observation of the OD ESR and electron cyclotron resonance (ECR) in the low-pressure gas over the sample are outlined. A possible application of ECR in the context of the OD ESR spectroscopy is suggested. 相似文献
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Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献
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Makarov AY Zhivonitko VV Makarov AG Zikirin SB Bagryanskaya IY Bagryansky VA Gatilov YV Irtegova IG Shakirov MM Zibarev AV 《Inorganic chemistry》2011,50(7):3017-3027
Interaction between Ph(3)P and 1,3,2,4-benzodithiadiazine (1); its 6,7-difluoro (2), 5,6,8-trifluoro (3) and 5,6,7,8-tetrafluoro (4) derivatives; and 5,6,8-trifluoro-3,1,2,4-benzothiaselenadiazine (5) proceeded via a 1:1 condensation to give Ph(3)P═N-R iminophosphoranes (1a-5a, R = corresponding 1,2,3-benzodichalcogenazol-2-yls), which are inaccessible by general approaches based on the Staudinger and Kirsanov reactions. In contrast, neither Ph(3)As nor Ph(3)Sb reacted with 1 and 4. Molecular structures of 1a-5a and 5 were confirmed by X-ray diffraction (XRD). The crystals formed by chiral molecules of 2a-5a were racemic, whereas the crystal of 1a was formed by a single enantiomer. In all of the Ph(3)P═N-R derivatives, one of the Ph rings is oriented face-to-face to the hetero ring, R. Upon heating to ~120 °C in squalane (1a, 3a, 4a) or dissolving in chloroform at ambient temperatures (1a, 2a, 4a), the Ph(3)P═N-R derivatives generated the 1,2,3-benzodithiazolyls (1b-4b, respectively) whose identity was confirmed by electron paramagnetic resonance (EPR). 2,1,3-Benzothiaselenazolyls 5b and 6b were detected by EPR as the main paramagnetic products of solution thermolysis of 5 and its 5,6,7,8-tetrafluoro congener (6), respectively. Passing a chloroform solution of 4a through silica column unexpectedly gave 5-6-6-6 tetracyclic (9) and 6-10-6 tricyclic (10) sulfur-nitrogen compounds, which were characterized by XRD. 相似文献
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Hyperfine Structure in the OD ESR Spectra of Recombining Charge Pairs in Doped Polyethylene Matrices
V.?N.?VerkhovlyukEmail author V.?I.?Borovkov V.?A.?Bagryansky S.?B.?Zikirin A.?I.?Taratayko O.?A.?Anisimov Yu.?N.?Molin 《Applied magnetic resonance》2018,49(4):345-355
The hyperfine structure has been resolved in the optically detected electron spin resonance (OD ESR) spectra of radical ion pairs generated by ionizing radiation at a low dopant concentration in a solid polyethylene matrix at room temperature. The different organic molecules that can capture electrons and holes were used as the dopants. The spin-lattice relaxation times T1 for radical ions of dopants were estimated to be tens of microseconds. The temperature dependence of OD ESR signal intensity indicates the diffusion-assisted mechanism of recombination of radical ion pairs in polyethylene. 相似文献
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Huawei Li Hong Liu C Eduardo Corrales Jessica R Risner Jeff Forrester Jeffrey R Holt Stefan Heller Albert SB Edge 《BMC neuroscience》2009,10(1):122
Background
Neural differentiation of embryonic stem (ES) cells is usually achieved by induction of ectoderm in embryoid bodies followed by the enrichment of neuronal progenitors using a variety of factors. Obtaining reproducible percentages of neural cells is difficult and the methods are time consuming. 相似文献9.
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