On the acceleration of ions from exploding clusters

An overview is provided of the rich dynamics that underlie the interaction of large, gas-phase clusters with intense optical radiation, resulting in the formation of highly charged clusters that subsequently undergo Coulomb explosion. We focus on those facets of the dynamics that determine the energies and yields of charged particles that are produced upon Coulomb explosion with a perspective on exercising control so as to explore the feasibility of schemes for table-top acceleration of charged particles. Illustrative examples are provided from recent work on atomic clusters, molecular clusters, and doped heteronuclear clusters.     

Evaluation of thermal diffusion factor and diffusion coefficient from measurements on a trennschaukel

Measurements have been taken on a glass trennschaukel of eight tubes for the Ar-He system as a function of composition and with its hot and cold bulbs at 100°c and 0°c. For each mixture, several speeds for the mechanical push-pull motion of the gas which cover a wide enough range were tried. The results have been interpreted to determine the thermal diffusion factor α _T, in conventional fashion as well as on the basis of a theory characterizing the low speed operation, developed here. Four such different possibilities of α _t evaluation are discussed and values compared with the traditional ones obtained from the convection-free two-bulb apparatus. Lastly we discuss also in brief the prospect of estimating the diffusion coefficient as an important byproduct from measurements on trennschaukel runs.     

Gold‐Nanoparticle‐Decorated Boron Nitride Nanosheets: Structure and Optical Properties

Synergetic cooperation of individual components of the nanocomposites (NCs) is responsible for their novel properties that lead to various technological applications. A simple chemical process depicting the deposition of functionalized gold nanoparticles on the surface of boron nitride nanosheets (BNNSs) in solution is reported. The structure, chemical composition, and optical properties of nanosheets are systematically studied. The deposition of Au nanoparticles on BNNS (BNNS_Au) results in plasmonic band modulation, thus altering the optoelectronic properties of BNNSs. The intense surface plasmon absorption band of BNNS_Au is narrowed and red‐shifted relative to the absorption band of as synthesized monometallic BNNSs. The observations reflect the strong interfacial interaction between BNNS and Au nanoparticles. This approach constitutes a basis for a simple process leading to the preparation of functionalized BNNSs and their utilization as nanoscale templates for assembly and integration with other nanoscale materials for futuristic optoelectronic devices.     

On the bremsstrahlung background correction to the high-energy Compton spectroscopy

methodology for bremsstrahlung (BS) background correction to extract a true Compton profile in high-energy Compton scattering experiments is presented. The BS background profiles for Hg, computed within the Born approximation, are estimated for different values of incident energy. It is seen for the first time that the BS background contribution in high-energy Compton profile experiments like those employing third generation synchrotron radiation sources comes out to be significant and non-linear. Further, it is found that the incorporation of BS correction in data reduction of such an experiment performed on Hg at 662 keV energy helps in reconciliation of theory and experiment.     

A study of pion absorption by16O using realistic interactions—I. Twonucleon emission following bound-pion absorption

Matrix element of the Galilean invariant non-relativistic reduction of the pseudoscalar-pseudovector interaction has been calculated assuming the reaction to be a direct process with boundπ ⁻ being absorbed by a correlated pair of nucleons. The Hartree-Fock wavefunctions obtained with the unitary-model-operator approach starting with the realistic nucleon-nucleon interaction have been used forπ-capturing nucleon pair in the initial state. The calculations have been done with and without antisymmetrising the initial state wavefunction of the pion absorbing pair. For the final state nucleon-nucleon interaction has been taken into account. The strongπ-nucleus interaction together with the Coulomb interaction with the finite nuclear size on the bound pion wavefunction are taken into account. Angular distributions of the emitted nucleon-pair, the branching ratios and the total absorption rates are calculated for¹⁶O with and without antisymmetrisation effect. The calculated results are compared with the experimental and other theoretical work.     

Conservation of channel spin in transfer reactions

The conservation of channel spin implying that the spin of the initial bound pair coupled to that of the initial free particle should result in the same channel spin as the spin of the final bound pair coupled to the spin of the final free particle, follows as a consequence of three-body theory of transfer reactions with the assumption of separability of two-bodyt-matrix. To test the validity of this principle we look at the experimental data on stripping reactions on even-even nuclei. We find that although reactions to channels not conforming to channel spin conservation are not altogether ruled out, the cross-sections of reactions violating channel spin conservation are much smaller than those conforming to channel spin conservation.