Investigation of the Coupling Potential by means of S-matrix Inversion

We investigate the inelastic coupling interaction by studying its effect on the elastic scattering potential as determined by inverting the elastic scattering $S$-matrix. We first address the effect upon the real and imaginary elastic potentials of including excited states of the target nucleus. We then investigate the effect of a recently introduced novel coupling potential which has been remarkably successful in reproducing the experimental data for the $^{12}$C+$^{12}$C, $^{12}$C+$^{24}$Mg and $^{16}$O+$^{28}$Si reactions over a wide range of energies. This coupling potential has the effect of deepening the real elastic potential in the surface region, thereby explaining a common feature of many phenomenological potentials. It is suggested that one can relate this deepening to the super-deformed state of the compound nucleus, $^{24}$Mg.Comment: 12 pages with 3 figure

A Systematic Investigation of Light Heavy-Ion Reactions

We introduce a novel coupling potential for the scattering of deformed light heavy-ion reactions. This new approach is based on replacing the usual first-derivative coupling potential by a new, second derivative coupling potential in the coupled-channels formalism. The new approach has been successfully applied to the study of the $^{12}$C+$^{12}$C, $^{12}$C+$^{24}$Mg, $^{16}$O+$^{28}$Si and $^{16}$O+$^{24}$Mg systems and made major improvements over all the previous coupled-channels calculations for these systems. This paper also shows the limitations of the standard coupled-channels theory and presents a global solution to the problems faced in the previous theoretical accounts of these reactions.Comment: 7 pages with 4 figure

Mapping Water Availability, Cost and Projected Consumptive Use in the Eastern United States with Comparisons to the West

The availability of freshwater supplies to meet future demand is a growing concern. Water availability metrics are needed to inform future water development decisions. Furthermore, with the help of water managers, water availability was mapped for over 1300 watersheds throughout the 31-contiguous states in the eastern U.S. complimenting a prior study of the west. The compiled set of water availability data is unique in that it considers multiple sources of water (fresh surface and groundwater, wastewater and brackish groundwater); accommodates institutional controls placed on water use; is accompanied by cost estimates to access, treat and convey each unique source of water, and; is compared to projected future growth in consumptive water use to 2030. Although few administrative limits have been set on water availability in the east, water managers have identified 315 fresh surface water and 398 fresh groundwater basins (with 151 overlapping basins) as Areas of Concern (AOCs) where water supply challenges exist due to drought related concerns, environmental flows, groundwater overdraft, or salt water intrusion. This highlights a difference in management where AOCs are identified in the east which simply require additional permitting, while in the west strict administrative limits are established. Although the east is generally considered water rich roughly a quarter of the basins were identified as AOCs; however, this is still in strong contrast to the west where 78% of the surface water basins are operating at or near their administrative limit. There was little effort noted on the part of eastern or western water managers to quantify non-fresh water resource

Reaction channel contributions to the helion optical potential

Background: The well-established coupled channel and coupled reaction channel processes contributing to direct reactions make particular contributions to elastic scattering that are absent from local density folding models. Very little has been established concerning the contribution of these processes to the optical model potentials (OMPs) for 3He scattering. For studying such processes, spin-saturated closed shell nuclei such as 16O and 40Ca are particularly suitable target nuclei and the (3He, 4He) reaction is easily handled within conventional reaction theory because it avoids complications such as breakup.Purpose: To establish and characterize the contribution to the 3He-nucleus interaction generated by coupling to neutron pickup (outgoing 4He) channels; also to study the contribution of collective states and identify effects of dynamical nonlocality from these couplings.Methods: Coupled reaction channel (CRC) calculations, including coupling to collective states, will provide the elastic channel S-matrix Sl j resulting from the included processes. Inversion of Sl j will produce the local potential that yields, in a single channel calculation, the elastic scattering observables from the coupled channel calculation. Subtracting the bare potential from the CRC calculations yields a local and l-independent representation of the dynamical polarization potential (DPP). From the DPPs, because of a range of combinations of channel couplings, the influence of dynamically generated nonlocality can be identified.Results: Coupling to 4He channels systematically induces repulsion and absorption in the 3He OMP and also a reduction in the rms radius of the real part. The repulsion and absorption is less for 208Pb than for the lighter target nuclei although the qualitative effects, including the general undularity of the DPPs, are similar for all cases; therefore coupling to these channels cannot be represented by renormalizing folding model potentials. Evidence is presented for substantial dynamical nonlocality of the induced DPPs; for 40Ca this modifies direct reaction angular distributions. The local equivalent DPPs for individual couplings cannot be added to give the overall DPP for the complete set of couplings. For the 208Pb case, channel coupling reduces the reaction cross section although it increases it for 16O, with 40Ca an intermediate case. Conclusions: The DPPs established here strongly challenge the notion that folding models, in particular local density models, provide a satisfactory description of elastic scattering of 3He from nuclei. Coupling to neutron pickup channels induces dynamical nonlocality in the 3He OMP with implications for direct reactions involving 3He. Departures from a smooth radial form for the 3He OMP should be apparent in good fits to suitable elastic scattering data

Diamond Nanowire Transistor with High Current Capability

Carrier confinement in nanowire (NW) structures can offer a host of new material properties compared to bulk electronic devices. Diamond can be considered an ultimate semiconductor given its superlative electronic, physical, and optical properties. However, the development of diamond device technology has been hindered by doping problems in conventional device structures. Here, heavily doped diamond NWs, some 15 nm wide and only 1–2 nm deep overcome these issues and offer a significant advance in NW technology; transistor action can be induced with remote side gates alone, without the need for semiconductor junctions. Quasi-ballistic transport is most-likely responsible for extraordinary current handling capability of the NW transistors fabricated here at some 20 MA cm−2, being around 0.04 G0. This unipolar technology opens up a new paradigm in diamond nanoelectronic device technology

Equation of state for nuclear matter based on density dependent effective interaction

An interesting method of obtaining equation of state for nuclear matter, from a density dependent M3Y interaction, by minimizing the energy per nucleon is described. The density dependence parameters of the interaction are obtained by reproducing the saturation energy per nucleon and the saturation density of spin and isospin symmetric cold infinite nuclear matter. The nuclear matter equation of state thus obtained is then used to calculate the pressure, the energy density, the nuclear incompressibility and the velocity of sound in nuclear medium. The results obtained are in good agreement with experimental data and provide a unified description of radioactivity, scattering and nuclear matter.Comment: 10 pages including 2 figure

Folding model analysis of alpha radioactivity

Radioactive decay of nuclei via emission of $\alpha$ particles has been studied theoretically in the framework of a superasymmetric fission model using the double folding (DF) procedure for obtaining the $\alpha$-nucleus interaction potential. The DF nuclear potential has been obtained by folding in the density distribution functions of the $\alpha$ nucleus and the daughter nucleus with a realistic effective interaction. The M3Y effective interaction has been used for calculating the nuclear interaction potential which has been supplemented by a zero-range pseudo-potential for exchange along with the density dependence. The nuclear microscopic $\alpha$-nucleus potential thus obtained has been used along with the Coulomb interaction potential to calculate the action integral within the WKB approximation. This subsequently yields microscopic calculations for the half lives of $\alpha$ decays of nuclei. The density dependence and the exchange effects have not been found to be very significant. These calculations provide reasonable estimates for the lifetimes of $\alpha$ radioactivity of nuclei.Comment: 7 pages including 1 figur

Optical model potentials involving loosely bound p-shell nuclei around 10 MeV/A

We present the results of a search for optical model potentials for use in the description of elastic scattering and transfer reactions involving stable and radioactive p-shell nuclei. This was done in connection with our program to use transfer reactions to obtain data for nuclear astrophysics, in particular for the determination of the astrophysical S_17 factor for 7Be(p,\gamma)8B using two (7Be,8B) proton transfer reactions. Elastic scattering was measured using 7Li, 10B, 13C and 14N projectiles on 9Be and 13C targets at or about E/A=10 MeV/nucleon. Woods-Saxon type optical model potentials were extracted and are compared with potentials obtained from a microscopic double folding model. We use these results to find optical model potentials for unstable nuclei with emphasis on the reliability of the description they provide for peripheral proton transfer reactions. We discuss the uncertainty introduced by the procedure in the prediction of the DWBA cross sections for the (7Be,8B) reactions used in extracting the astrophysical factor S_17(0).Comment: 16 pages, LaTEX file, 9 figures (PostScript files

A Global Potential Analysis of the 16^{16}O+28^{28}Si Reaction Using a New Type of Coupling Potential

A new approach has been used to explain the experimental data for the $^{16}$O+$^{28}$Si system over a wide energy range in the laboratory system from 29.0 to 142.5 MeV. A number of serious problems has continued to plague the study of this system for a couple of decades. The explanation of anomalous large angle scattering data; the reproduction of the oscillatory structure near the Coulomb barrier; the out-of-phase problem between theoretical predictions and experimental data; the consistent description of angular distributions together with excitation functions data are just some of these problems. These are long standing problems that have persisted over the years and do represent a challenge calling for a consistent framework to resolve these difficulties within a unified approach. Traditional frameworks have failed to describe these phenomena within a single model and have so far only offered different approaches where these difficulties are investigated separately from one another. The present work offers a plausible framework where all these difficulties are investigated and answered. Not only it improves the simultaneous fits to the data of these diverse observables, achieving this within a unified approach over a wide energy range, but it departs for its coupling potential from the standard formulation. This new feature is shown to improve consistently the agreement with the experimental data and has made major improvement on all the previous coupled-channels calculations for this system.Comment: 21 pages with 12 figure