Covalence reduction factors of four-coordinated pseudo-tetrahedral paramagnetic compounds inD 2d symmetry

Theoretical expressions for the covalence reduction factors of orbital angular momentum and spin-orbit coupling in pseudo-tetrahedral four-coordinated paramagnetic complexes withD _2d symmetry, denoted ask's andR's respectively, have been derived. p ]The mixing coefficients in the antibonding MO's for the CuCl ₄ ^2- ion in three complexes are estimated using suitable approximations. It is shown thatk's must be less thanR's in Tinkham's approximation. Certain misconceptions existing in the literature regarding the value of the integral 〈p _u |???u|s〉 have been clarified.     

Studies of mass and energy correlations in thermal neutron fission of U-235 accompanied by long range alpha particles

Several characteristics of fission accompanied by long range alpha particles (LRA) have been studied in the thermal neutron induced fission of²³⁵U. The kinetic energies of fission fragments and the LRA were measured with a back-to-back ionization chamber and semiconductor detectors respectively. The kinetic energies of the two fragments and the LRA in LRA fission, along with the energies of pair fragments in the normal binary fissions, were recorded event by event on a magnetic tape by means of a four-parameter data acquisition system. The data were analysed to study the dependence of different quantities in LRA fission on the fragment mass ratio, LRA energy and the total kinetic energy of the fission fragments. It is seen that the most probable energy of LRA increases significantly for near symmetric mass divisions. The total kinetic energy for all mass ratios in LRA fission is found to be (2.6±0.7) MeV larger than that in binary fission. The difference in the total kinetic energies in LRA and binary fissions is seen to be dependent on mass ratio. This result may suggest that the scission configuration in LRA fission is different for different mass ratios. Correlations between the fission fragment and LRA energies have been studied for several mass ratios. It is seen that the most probable fragment kinetic energyĒ _k varies nearly linearly with the LRA energyE _a for various mass divisions but the variation of the most probable LRA energyĒ _a with fragment kinetic energyE _k is found to deviate from linearity for several mass ratios. From a least square fit to the variation ofĒ _k withE _a it is found that the slope (dĒ _k/dE_a) increases with the increase in mass ratio. The present results are discussed to arrive at a better understanding of the scission configuration in the fission accompanied by LRA emission.     

Bare quark masses from the transverse cut offs ine + e − interactions

From the transverse cuts off of the electron positron annihilation in the SPEAR II regime, we obtain positivity domains of bare quark masses.     

Interaction of 4-nitroquinoline-1-oxide with indole derivatives and some related biomolecules: a study with magnetic field

Laser flash photolysis and an external magnetic field have been used for the study of the interaction of 4-nitroquinoline-1-oxide (4NQO) with some indole derivatives, amino acids, tyrosine and tryptophan, and model proteins, lysozyme and bovine serum albumin. In an aprotic medium, photoinduced electron transfer (PET) from indoles to 4NQO is accompanied by proton transfer from the indole moieties irrespective of the substitution at the N-1 position. For 1,2-dimethylindole, however, proton abstraction is hindered possibly due to steric effects. In a protic medium, obviously proton transfer is possible from the medium and is the dominating reaction following PET. The effect of an external magnetic field is very small for all the systems studied. This is attributed to a competition between geminate proton abstraction by the 4NQO radical anion from the partner radical cation and escape of the 4NQO radical anion to the medium followed by proton transfer. The latter process is more predominant, and the former one, which produces a small population of geminate spin-correlated radical pairs, leads to a minor field effect. Another interesting observation is the affinity of 4NQO toward the tryptophan residues in a protein environment. It is seen that PET takes place preferably from the tryptophan residues rather than from the tyrosine residues.     

Study of electron donor-acceptor complexes of tri-n-octyl amine with [60]- and [70]fullerenes and some other electron acceptors by absorption spectrophotometric method

Electron donor-acceptor (EDA) complexes of tri-n-octylamine (TOA) with [60]- and [70]fullerenes and some other electron acceptors have been studied in chloroform medium by absorption spectrophotometric technique. Charge transfer (CT) absorption bands are observed in the visible region. Vertical ionization potential of TOA was determined utilizing CT transition energy. Oscillator strengths, transition dipole strengths and resonance energies for all the complexes have been calculated. [60]Fullerene/TOA and [70]fullerene/TOA complexes are found to decay slowly with time. Kinetics of these reactions have been studied and activation energies for such processes have been estimated. Ab initio calculations suggest that complexation of [70]fullerene with TOA is enthalpy favoured.     

Vibrational spectroscopy of Cm-C/Cb-Cb stretching vibrations of copper tetramesityl porphyrin: An algebraic approach

Using Lie algebraic techniques and simpler expressions of the matrix elements of Majorana and Casimir operators given by us, we obtain an effective Hamiltonian operator which conveniently describes stretching vibrations of biomolecules. For a copper tetramesityl porphyrin molecule, the higher excited vibrational levels are calculated by applying the U(2) algebraic approach.     

Slope and curvature of Isgur-Wise function using variationally improved perturbation theory in a quantum chromodynamics inspired potential model

We used variationally improved perturbation theory (VIPT) in calculating the slope and curvature of Isgur-Wise (I-W) function with the Cornell potential −$ \frac{{4\alpha _s }} {{3r}} $ \frac{{4\alpha _s }} {{3r}} +br + c instead of the usual stationary state perturbation theory as done earlier. We used −(4α _s /3r), i.e. the Coulombic potential, as the parent and the linear one, i.e. br+c as the perturbed potential in the theory and calculated the slope and curvature of Isgur-Wise function including three states in the summation involved in the first-order correction to wave function in the method.     

Vibrational spectroscopy of bio-molecules: an algebraic approach

Porphyrins have received numerous considerable attentions during recent years because of their great biological importance. The most interesting areas of current research in molecular spectroscopy are the study of the vibrational ground and excited states of polyatomic molecules especially for the Metalloporphyrins. In this paper, we have calculated the fundamental and extrapolated vibrational energy levels of Magnesium, Nickel, Copper, Zinc, Metalloporphyrin molecules using U (2) algebraic model Hamiltonian. The results obtained by this method are in good agreement with the experimental data. This study gives a general approach for solving the vibrational spectra of Metalloporphyrin molecules.     

Luminescence study of SHI irradiated nano semiconductor: Conducting polymer composite

Semiconductor nanoparticle and conducting polymer composite is an interesting class of materials for optoelectronic and photovoltaic device application. We have synthesized a composite of nanocrystalline PbS and conducting polymer MEH-PPV by chemical synthesis and studied the effect of swift heavy ion (SHI) irradiation on the composite material. The irradiation of the composite materials in thin film form is carried out with 120 MeV Si⁺⁹ ion beam at fluences from 5×10¹⁰ to 10¹³ ions/cm². Fluence dependent optical and structural properties have been observed in optical absorption, PL and TEM studies. Reduction of nanoparticle size has been observed after irradiation.