Shape Of Energy Spectrum Research Articles

On the continuum shape of gamma-ray burst energy spectra

The analysis of SIGNE experiment data shows that the theoretical laws we have tested assuming a single component continuum probably do not describe the real phenomenon of gamma emission and that there is a very fast spectral evolution, possibly on timescales down to 16 ms. Moreover we have not found a universal value of a for the relation F = (kT) α /3/, but rather a gradual decrease of the spectral hardness index during pulses.

Multiple scattering effects for quasifree scattering in 3He(d, dd) 1H breakup reaction

The differential cross sections for the 3He(d, dd) 1H breakup reaction have been measured in the kinematical region corresponding to quasifree scattering (QFS). The angular dependence of the cross section at the minimum laboratory energy of the unobserved proton has been obtained. The shapes of energy spectra are approximately reproduced by a calculation in the plane-wave impulse approximation (PWIA). As for the angular dependence of the cross section and for the absolute values, the calculation fails to reproduce the experimental results. A calculation with multiple scattering effects reproduces the experimental data well, not only for the shape of the energy spectra but also for the angular dependence. For the absolute cross sections, the ratio of the experimental values to the calculated ones with multiple scattering effects is 0.7 and this value is improved compared with the value of 0.3 obtained by the PWIA calculation.

Charge distribution of multiply charged ions scattered from tungsten

The authors have measured the charge state distribution of 20 keV multiply charged Ne, Ar and Kr ions scattered from a polycrystalline tungsten target. For primary charge states up to 8+ only singly and doubly charged reflected particles are observed. However, when the primary charge state exceeds 8+, scattering into triply charged ions does occur and the shapes of the respective energy spectra also change. An explanation is given in terms of autoionisation processes occurring when the scattered particle leaves the surface in a highly excited state.

Ion-atom interaction potential effects on the shape of energy spectra of ions backscattered by a thick target

Abstract Based on the general Gaudsmit-Saunderson-Lewis model for multiple scattering in a semi-infinite medium, an expression accounting for the effects of multiple scattering on the shape of the backscattering energy spectrum has been obtained. This expression is represented by a series of ion angular distribution moments. The limits of the applicability of the small-angle approximation to the description of multiple scattering are defined. It is shown that the sensitivity of the angular distribution moments of multiple scattered ions to the type of ion-atom potential increases with an increase in the moment order. The possibility of investigation of the ion-atom interaction potential experimentally over a wide range of impact parameters by the backscattering method is discussed.

Muon decay: Measurement of the positron polarization and implications for the spectrum shape parameter η, V-A and T-invariance

A new measurement of the longitudinal polarization P L of the e + from μ + decay is presented here. Combined with our previously published result, we obtain P L = 0.998 ± 0.045 (statistical plus systematic error). We also report on the first measurement of P L( θ) where θ is the angle between the e + line of flight and the μ + polarization. The implications on the “low energy spectrum shape parameter η″, on the ratio of A coupling to V coupling and on time-reversal are discussed. The results are in agreement with the standard V-A form of the charged leptonic weak interaction.

Shape of energy spectrum of hadrons at sea level

The energy spectrum of cosmic-ray hadrons between 10 GeV and 10 TeV at sea level was calculated by using a Monte-Carlo method. The results show a strong steepening of the hadron spectrum at about 200 GeV. The change in the spectral slope is interpreted as a combined effect due to the energy-dependent production cross section of hadron-air-nucleus collisions and the saturation of the relative intensity of pions in the hadron family. The magnitude of the change is found to vary from 0.5 to 0.7 depending on the form of the production cross section. The results agree with the experimental spectra obtained by the Turku double neutron monitor.

A search for incomplete fusion from the shapes of residue energy spectra

It is shown that information on the reaction mechanism of heavy ion reactions can be gained by inspecting the shape of residue energy spectra. The method is used with data from the 20Ne + 12C reaction at E( 20Ne) = 160 MeV . For this case all residue energy spectra are well described by compound nucleus evaporation.

(e,e'p) reactions: Present status and future trends

The present status of quasi-free scattering (e,e'p) experiments is reviewed. Some aspects of hole states momentum and energy distributions from medium nuclei are discussed, like the high momentum region, the shape and width of energy spectra for deep hole states, and the sum rule problems. Recent results on deuterium and 3He are presented and various contributions to the d(e,e'p)n reaction other than quasi-free e.p scattering are examined. Brief comments are made on (e,e'n) and (e,e'2N) reactions which will be some important challenges for the next generation of electron accelerators.

A new technique to study the stages of oxidation of metals using oxidation induced changes in the shape of secondary ion energy spectra

A new technique to study the oxidation process in metals based on the yield variation with oxygen dose of secondary ions whose ejection mechanisms are identified with distinctly different dynamical sputtering processes is presented. When applied to a polycrystalline copper sample the method identifies four possible oxidation stages, from adsorption into the surface layer for doses up to about 10 4L, followed by a rapid reconstruction to a Cu 2O structure at 10 4L, followed by a slow growth of bulk oxide up to 10 4L and a further physisorption of oxygen or transition to a surface CuO structure at higher doses. The technique provides a significant increase in the versatility and usefulness of SIMS equipment incorporating appropriate energy analysis facilities.

Quasi-Elastic Neutron Scattering Study of Aqueous Solutions of FeCl3, NiCl2 and MgCl2

Quasi-elastic neutron scattering experiment was performed on FeCl 3 , NiCl 2 and MgCl 2 aqueous solutions. The whole shape of energy spectra of incoherently scattered neutrons was analyzed. The hydration number of Fe 3+ ion was estimated to be 2.6, being independent of solute concentration. Based on a jump diffusion model, the diffusion constant and the rest time for the water molecules bound to Ni 2+ ion in the NiCl 2 solution were estimated as 0.2×10 -5 cm 2 sec -1 and 3.0×10 -12 sec at 25°C, and 0.6×10 -5 cm 2 sec -1 and 2.0×10 -12 sec at 55°C, respectively. Those to Mg 2+ ion in the MgCl 2 solution were estimated as 0.8×10 -5 cm 2 sce -1 and 3.0×10 -12 sec at 25°C, respectively. The present results justify the structure model proposed by Brady et al . for the FeCl 3 solution and the simplified “hard sphere model” originally proposed by Quirke et al . for the NiCl 2 solution. The diffusion process of Mg 2+ ion in the MgCl 2 solution is discussed.

Quasi-elastic neutron scattering study of AlCl 3 aqueous solution

Quasi-elastic neutron scattering from protons in AlCl 3 aqueous solution has been measured by the use of a triple-axis spectrometer. Assuming the existence of two different kinds of water molecules, either in free state or in bound state, the whole shape of energy spectra of scattered neutrons was analyzed. About eight water molecules were found to be bound to an Al ion, being almost independent of the solute concentration. The diffusion constant, the rest time and the jump length of the remaining free water molecules were estimated based on a jump diffusion model.

Study of low energy noble gas ion reflection from monocrystalline surfaces; influence of thermal vibrations of the surface atoms: I. Computer simulation of energy and spatial distributions

The influence of target temperature on the energy and spatial distributions of low energy noble gas ions, multiply reflected from a monocrystalline surface, has been studied by computer simulation. The results are obtained by using the chain model; this simplification is a good approximation when the surface is bombarded along low index directions. The simulation model is outlined briefly. The consequences of different target temperatures on the shape of energy spectra of specularly reflected particles and on the shape of spatial distributions if the total scattering angle, resp. angle of incidence is fixed, are discussed qualitatively. Calculations of 6 keV Ar + ions reflected from a vibrating Cu 〈100〉 chain are discussed using these qualitative considerations. The shape.of both the energy and the spatial distributions appears to be distinctly temperature dependent under certain conditions.

Use of the nuclear reaction 16O(d,α) 14N in the microanalysis of oxide surface layers

The nuclear reaction 16O(d,α) 14N induced by 900 keV deuteron bombardment has been used in concentration profile measurements of oxygen in oxide surface layers. The concentration profile can be deduced from the shape of experimental energy spectra of α-particles. The method has been applied in investigations of silicon oxide layers thermally grown on silicon of thicknesses from 2000 Å up to 12 000 Å. The influence of energy straggling, energy resolution, and experimental geometry on the depth resolution is discussed.

Energy spectra of auroral zone particles

Two sounding rockets were launched into auroral breakups near local midnight and one rocket was launched into a 2.5-db riometer absorption event at local noon. The rockets were instrumented to measure the energy spectra of electrons and protons. Results show that electron fluxes in the auroral zone resemble electron fluxes in the plasma sheet, both in the shape of energy spectra and in the magnitude of flux, which indicates that the plasma sheet may be the source of auroral zone electrons. The proton fluxes in these two regions are quite different. Thus the plasma sheet probably is not the source of auroral zone protons. Time variations of 1-kev electrons and protons were coherent, which indicates similar precipitation mechanisms for these two types of particles. The source of 1-kev electrons was found to have a wider spatial extent than the source of 10-kev electrons. During auroral breakup, electron precipitation was isotropic over the upper hemisphere while the protons were anisotropic, with more flux at 90° than at 0°.

Determination of Nuclear Reaction Mechanisms From Energy Spectra of Emitted Particles

Energy spectra of deuterons and tritons from ($p, d$) and ($p, t$) reactions are found to be peaked near their maximum energy, in contrast to the spectra of protons from ($d, p$) and ($t, p$) reactions which are peaked at low energy. It is shown that this characteristic of inverse reactions is to be expected from "stripping" and "pickup" reactions as a consequence of the fact that the former excite "particle" states while the latter excite "hole" states, but that it is not expected from collision type reaction mechanisms (e.g., "knockout"). It is thus concluded that ($t, p$) and ($p, t$) reactions as well as ($d, p$) and ($p, d$) reactions proceed by "stripping" and "pickup". The shape of energy spectra from ($p, \ensuremath{\alpha}$) and ($\ensuremath{\alpha}, p$) reactions indicates that the non-compound-nucleus portion of these also goes by "pickup" and "stripping"; there is corroboratory evidence for this from absolute cross sections.

The Indirect (p,d) Process

In 300-Mev proton bombardment of various targets highenergy deuterons have been observed ejected at large angles where direct pick-up deuterons were improbable. For these deuterons, the dependence of the cross section on the mass number of the target nucleus suggests an indirect pick-up process, induced by seoondary nucleons which are produced hy one or more collisions of the primary proton in the same nucleus. With some assumptions about the pick-up probability of the secondary nucleons, the indirect prooess hypothesis is shown to give results consistent with the experimental data on energy spectrum shape and angular dependence of the deuterons. In the present note a calculation is made of the effective pick-up probability considering the attenuation effects of produced deuterons. (A. C.)