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91.
2-Aminopyridinium maleate (2APM) is a recently discovered organic acid-base complex that crystallizes in a non-centrosymmetric space group Pc and hence has a nonzero second-order optical susceptibility. In 2APM the cation (aminopyridinium ion) is connected to the anion (maleate ion) through hydrogen bonds (N1-H10–O2 and N2-H12–O1), we have calculated the molecular properties of 2APM for varying strength of these hydrogen bonds. It is observed that the molecular hyperpolarizabilty varies for varying strength of these hydrogen bonds. These observations are interpreted in terms of the change in nature of the hydrogen bond interaction as its strength is varied. Macropscopic second-order optical susceptibility (d 0) of 2APM is obtained using the calculated value of molecular hyperpolarizability and the reported crystal structure of 2APM. In order to study the influence of molecular packing on the macroscopic non-linear optical property of the crystal, susceptibility calculations are repeated for 2-methyl-4nitroaniline (MNA) crystal, which is a very well known non-linear optical organic crystal with an exceptionally high value of second-order optical susceptibility. A comparison between the non-linear optical property of 2APM and MNA crystals is given. Comparing the values of d 0 of 2APM crystals with that of urea shows that the nonlinear optical response of 2APM crystals will be nearly 10 times that of a urea crystal. 相似文献
92.
S Kailas A Navin A Chatterjee P Singh A Saxena D M Nadkarni D C Biswas R K Choudhury S S Kapoor 《Pramana》1993,41(4):339-344
The measurements of fission fragment angular distributions for the system19F+232Th have been extended to the sub-barrier energies of 89.3, 91.5 and 93.6 MeV. The measured anisotropies, within errors are
nearly the same over this energy region. However, the deviation of the experimental values of anisotropies from that of standard
statistical model predictions increases as the bombarding energy is lowered. 相似文献
93.
Amitava Choudhury 《Journal of Chemical Sciences》2002,114(2):93-105
A new iron fluorophosphate of the composition, [C6N4H21] [Fe2F2(HPO4)3][H2PO4]·2H2O,I has been prepared by the hydrothermal route. This compound contains iron fluorophosphate layers and the H2PO4
- anions are present in the interlayer space along with the protonated amine and water molecules. The compound crystallizes
in the monoclinic space group P21/c.(a = 13.4422(10) ?,b = 9.7320(10) ?, c = 18.3123(3) ?, β= 92.1480°,V= 2393.92(5) ?3, Z = 4,M = 719.92,d
calc. = 1.997 g cm-3, R1 = 0.03 andwR
2= 0.09). 相似文献
94.
Junction conditions are studied at the boundary of a sphere consisting of a charged viscous fluid with outgoing heat and radiation flux. The motion is anisotropic and the matching is done with the exterior Reissner-Nordström-Vaidya metric. A general relation in terms of the energy-momentum tensor componentsT
1
1
andT
4
1
is satisfied at the boundary hypersurface and this relation gives appropriate physical conditions in different special cases, some of which were obtained previously. 相似文献
95.
P. Chakrabarti S. C. Choudhury B. B. Pal 《Applied Physics A: Materials Science & Processing》1989,48(4):331-334
The noise generated due to randomness of multiplication process in the avalanche region of an Al
x
Ga1–x
As/GaAs quantum well p+-i-n+ structure has been studied. The paper presents a quantitative evaluation of the noise performance of the superlattice APD which has not been done so far. Further, useful design data for low noise structure is given. 相似文献
96.
97.
The transversity distribution of quarks in a nucleon is one of the three fundamental distributions, that characterize nucleon's
properties in hard scattering processes at leading twist (twist 2). It measures the distribution of quark transverse spin
in a nucleon polarized transverse to its (infinite) momentum. It is a chiral-odd twist-two distribution function — gluons
do not couple to it. Quarks in a nucleon/hadron are relativistically bound and transversity is a measure of the relativistic
nature of bound quarks in a nucleon. In this work, we review some important aspects of this less familiar distribution function
which has not been measured experimentally so far. 相似文献
98.
Using the crystal structure, a comprehensive interpretation of the origin of ferroelectricity in the hydrogen bonded triglycine
family of crystals is given. Our detailed analysis showed that the instability of nitrogen double well potential plays a driving
role in the mechanism of the ferroelectric transitions in these crystals. 相似文献
99.
S.C.L. Sharma G.K. Mehta R.K. Choudhury D.M. Nadkarni S.S. Kapoor 《Nuclear Physics A》1981,355(1):13-24
The emission probabilities per fission of α-particles, tritons and protons have been measured in fast neutron induced fission of 235U. The measurements were carried out at neutron energies of 120, 180, 230 and 550 keV. AΔE-E semiconductor detector telescope was used to identify different light charged particles and the fission fragments were detected with an ionization chamber. The three-parameter data corresponding to the pulse heights from the ΔE-E detectors and the ion-chamber were recorded event by event on magnetic tape and were analyzed off-line by computer. No significant variation in the most probable energy () and the standard deviation (σE) of the energy spectra of different light charged particles with incident neutron energy was observed, although was seen to have a slightly higher value beyond En = 230 keV. The yield of α-particles in fission induced by neutrons of En ~ 200 keV was found to be higher by about 20 % than that in thermal neutron induced fission. The yields of tritons and protons were found to increase significantly with neutron energy. 相似文献
100.
Quantum chromodynamics based isovector isoscolar particle mixing arising out of isospin violating quark mass differences has been used to construct a new charge-symmetry breaking Λ-N interaction element. It appears that vector meson exchanges between N and a physical Λ rather than pseudoscalar exchanges provide the largest contribution to explain the binding energy difference between the mirror hyper-nuclei ΛHe4 and ΛH4. Prediction of the model to Λn and Λp scattering lengths have been compared with those obtained from the combined analysis of ΛN scattering and s-shell hyperfragment data. We find satisfactory agreement of our results. 相似文献