Structure of nuclear transition matrix elements for neutrinoless double-<Emphasis Type="Italic">β</Emphasis> decay

The structure of nuclear transition matrix elements (NTMEs) required for the study of neutrinoless double-β decay within light Majorana neutrino mass mechanism is disassembled in the PHFB model. The NTMEs are calculated using a set of HFB intrinsic wave functions, the reliability of which has been previously established by obtaining an overall agreement between the theoretically calculated spectroscopic properties and the available experimental data. Presently, we study the role of short-range correlations, radial evolution of NTMEs and deformation effects due to quadrupolar correlations. In addition, limits on effective light neutrino mass 〈m _ν 〉 are extracted from the observed limits on half-lives T ₁^2/0ν of neutrinoless double-β decay.     

A complete Raman mapping of phase transitions in Si under indentation

Crystalline Si substrates are studied for pressure‐induced phase transformation under indentation at room temperature (RT) using a Berkovich tip. Raman spectroscopy, as a nondestructive tool, is used for the identification of the transformed phases. Raman lines as well as area mapping are used for locating the phases in the indented region. Calculation of pressure contours in the indented region is used for understanding the phase distribution. We report here a comprehensive study of all the phases of Si, reported so far, leading to possible understanding of material properties useful for possible electromechanical applications. As a major finding, distribution of the amorphous phase in the indented region deviates from the conventional wisdom of being in the central region alone. We present phase mapping results for both Si(100) and Si(111) substrates. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman probe to estimate surface energies of embedded semiconductor nanostructures

Embedded semiconductor nanoclusters (nc‐) of GaN, Si and InN were grown using the ion‐implantation technique and subsequent annealing. Detailed phonon properties were studied for the identification of the grown phases as well as to estimate the stress developed in these embedded structures. The surface energies of the embedded nanoclusters were calculated in analogy with the stressed spherical nanoclusters and excess pressure in a liquid drop. The estimated surface energies for nc‐GaN ∼4 Nm⁻¹, nc‐InN ∼2.7 Nm⁻¹ and nc‐Si ∼1.4 Nm⁻¹ are discussed in the light of possible phase transition in the nanocrystalline systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Double charge transfer cross sections in collision of protons with helium atom

Theoretical total cross sections for the double charge transfer in proton-helium collisions are analysed using the four-body boundary corrected continuum intermediate state approximation in the energy range of 30 to 500 keV. We have also obtained differential double capture cross sections as a functions of projectile scattering angle. The intermediate continuum state of each of the active electron has been taken into account in this formalism. Our calculated results are compared with the previous experimental and theoretical values. The agreement is very encouraging.     

Physical characterisation of 4′-butyl-4-heptyl- bicyclohexyl-4-carbonitrile

We report measurements of birefringence, bend elastic constant, principal dielectric constants and conductivities as functions of temperature in the nematic phase of 4′-butyl-4-heptyl-bicyclohexyl-4-carbonitrile (CCN-47). The compound exhibits a small birefringence and a large negative dielectric anisotropy. Surprisingly, it shows a negative conductivity anisotropy, which probably owes its origin to the structural details of the molecules. The orientational order parameters (S) are estimated from both birefringence and dielectric anisotropy, and they agree well in the entire nematic range. The experimental results are compared with those on CCH7, which has a similar core structure but with a longitudinal dipole moment, in place of the transverse one of CCN-47.