Deuteron Spectra Research Articles

Deuteron spin-lattice relaxation in partly and fully deuterated [formula omitted

Deuteron spin-lattice relaxation and spectra were studied in partially and fully deuterated ( NH 4 ) 2 PdCl 6 in the temperature range 5–300 K. The relaxation rate maximum was observed at 45 K in ( ND 4 ) 2 PdCl 6 . Its value is reduced due to limited jumps by about 33% relative to the theoretical value expected for threefold reorientations. Limited jumps correspond to an N–D vector jumping between six directions on a cone around a Pd–N vector, the angle between the N–D and Pd–N vectors being denoted Δ . This motion makes a part of the quadrupole interaction ineffective in relaxation thus reducing the maximum rate at 45 K. The observed reduction leads to the value Δ = 21 ∘ . Limited jumps are quenched to a large extent at the order–disorder phase transition and consequently a decrease is observed in the rate. Below the transition ND 4 + ions reorient between the tetrahedral orientations of the ordered phase, therefore the quadrupole interaction has the full relaxing efficiency. In the 10% deuterated sample the temperature of the rate maximum is shifted to 35 K and below 20 K the rate itself is one order of magnitude larger than in ( ND 4 ) 2 PdCl 6 . The increase is related to (1) the absence of the order–disorder phase transition and (2) to the enhanced mobility of NH 3 D + because of its electric dipole moment. Limited jumps are claimed to be the dominant relaxation mechanism below 20 K. The relaxation in the disordered 30% deuterated sample is quite similar to that in 10% sample. The 50% and 70% deuterated samples undergo a transition to the ordered phase. The relaxation is biexponential with the characteristic rates somewhat smaller than those in ( ND 4 ) 2 PdCl 6 , but approaching them with increasing deuteration. This variation can be explained with different mobilities and varying relative numbers of the various isotopomers NH 4 - n D n + , n = 1 – 4 .

Deuteron NMR relaxation, spectra, and evidence for the order-disorder phase transition in (ND4)2PtCl6

Deuteron NMR relaxation and spectra were studied at the resonance frequency of 46 MHz in polycrystalline (ND(4))(2)PtCl(6) between 300-5 K. The relaxation rate maximum near 50 K is about 53% smaller than the calculated maximum related to 120 degrees rotations about the threefold symmetry axes of the ammonium ion. The difference is explained by assuming for a N-D vector a total of 24 equilibrium directions, which in groups of six deviate from the nearest Pt-N vector by a certain angle Theta. So-called limited jumps between the directions of each group take place much more frequently than the large-angle rotations, thus rendering a fraction of the deuteron quadrupole coupling ineffective in relaxation. A motional model is presented, which takes into account both these motions simultaneously. A comparison with experimental data leads to Theta=26.0 degrees , in reasonable agreement with earlier neutron diffraction data. A sharp decrease found in the relaxation rate at the order-disorder phase transition temperature of 27.2 K is related to the fact that one of the six equilibrium directions becomes preferred. This leads to a formation of ordered domains, in which the active motion driving the relaxation is 120 degrees rotations. Two components in the spectra found below 55 K are related to domains (broad) and transition regions between domains (narrow). Reasons for the nonexponentiality observed below 20 K are discussed, the most likely explanation being that limited jumps dominate within transition regions and make the corresponding deuterons relax faster than those in domains.

Gamma-delayed deuteron emission of the [formula omitted] halo state

M1 transitions from the Li 6 ( 0 + ; T = 1 ) state at 3.563 MeV to the Li 6 ( 1 + ) ground state and to the α + d continuum are studied in a three-body model. The bound states are described as an α + n + p system in hyperspherical coordinates on a Lagrange mesh. The ground-state magnetic moment and the gamma width of the Li 6 ( 0 + ) resonance are well reproduced. The halo-like structure of the Li 6 ( 0 + ) resonance is confirmed and is probed by the M1 transition probability to the α + d continuum. The spectrum is sensitive to the description of the α + d phase shifts. The corresponding gamma width is around 1.0 meV, with optimal potentials. Charge symmetry is analyzed through a comparison with the β-delayed deuteron spectrum of 6He. In 6He, a nearly perfect cancellation effect between short-range and halo contributions was found. A similar analysis for the Li 6 ( 0 + ; T = 1 ) γ decay is performed; it shows that charge-symmetry breaking at large distances, due to the different binding energies and to different charges, reduces this effect. The present branching ratio Γ γ ( 0 + → α + d ) / Γ γ ( 0 + → 1 + ) ≈ 1.3 × 10 −4 should be observable with current experimental facilities.

Evolution of intranuclear collisions at intermediate energies

The experimental data on energy and multiplicity distributions of protons and momentum spectra of deuterons emitted in the reactions of pions and protons of energy ranging from 2.5 to 200 GeV with several nuclei are compared to the calculations based upon two different model approaches: DCM Monte Carlo [3] code and the tube-fireball (TF) model [4]. The results of this confrontation are discussed within the framework of the intranuclear interaction mechanism assumed. A detailed study of the intranuclear scenario presented by the DCM Monte Carlo program gives grounds to build simplified analytic models like the TF which may turn out to be very useful in many practical problems as being of a predictive nature.

Study of spatial structure and energy spectrum of ion beams by means of LR 115A and PM-355 nuclear track detectors

The paper reports on measurements of pulsed plasma-ion streams, as performed with the selected solid-state nuclear track detectors (SSNTD). The ion-beams were produced by an experimental device (RPI-IBIS) equipped with coaxial electrodes (each made of molybdenum rods) and a fast-acting gas valve. The device was operated at 30 kV/44 kJ, with puffing of pure hydrogen or deuterium. The spatial structure of the ion beams was studied with pinhole cameras equipped with replaceable detectors, and ion mass- and energy-spectra were measured with a Thomson spectrometer. To analyse low-energy ions (below the energy thresholds of LR 115A and PM-355 SSNTD) an additional accelerating system was applied. It was observed that ions of energy > 30 keV are emitted in bunches, and the ion flux amounts to 2 × 10 12 ions / cm 2 at a distance of 30 cm from the electrodes outlet. Energy spectra of protons and deuterons ranged from about 30 keV to about 400 keV. The ion distributions, as recorded by means of the PM-355 and LR 115A detectors, are similar.

Deuteron and Antideuteron Production inAu+AuCollisions atsNN=200 GeV

The production of deuterons and antideuterons in the transverse momentum range 1.1<p(T)<4.3 GeV/c at midrapidity in Au+Au collisions at square root of s(NN)=200 GeV has been studied by the PHENIX experiment at RHIC. A coalescence analysis, comparing the deuteron and antideuteron spectra with that of proton and antiproton, has been performed. The coalescence probability is equal for both deuterons and antideuterons and it increases as a function of p(T), which is consistent with an expanding collision zone. Comparing (anti)proton yields, p /p=0.73+/-0.01, with (anti)deuteron yields, d /d=0.47+/-0.03, we estimate that n /n=0.64+/-0.04. The nucleon phase space density is estimated from the coalescence measurement.

Explosion characteristics of intense femtosecond-laser-driven water droplets

An efficient acceleration of energetic ions is observed when small heavy-water droplets of approximately 20 microm diameter are exposed to ultrafast (approximately 40 fs) Ti:sapphire laser pulses of up to 10(19) W/cm2 intensity. Quantitative measurements of deuteron and neutron spectra were done, allowing one to analyze the outward and inward directed deuteron acceleration from the droplet. Neutron spectroscopy based on the D (d,n) fusion reaction was accomplished in four different spatial directions. The energy shifts of those fusion neutrons produced inside the exploding droplet reflect a remaining deuteron acceleration inside the irradiated droplet along the axis of the incident laser beam. The overall neutron yield of the microdroplets is relatively small as a result of the dominant outward directed acceleration of the deuterons with 1200 neutrons/shot. Relying on the "explosion-like" acceleration of such spherical droplet targets we have developed a spray target consisting of heavy-water microspheres with diameters of 150 nm . Both the high deuteron energies of up to 1 MeV resulting from the irradiation intensity of approximately 10(19) W/cm2 as well as the collisions between the deuterons and the surrounding spray delivered about one order of magnitude more neutrons than the single-droplet system. The approximately 6 x 10(3) neutrons per laser pulse from the spray can be attributed to an efficient deuteron release from a significantly smaller laser excited volume as from deuterium-cluster targets.

Further Study and Analysis of the 7 Li on 56 Fe Reaction at 50 MeV Incident Energy

We present deuteron and triton spectra measured at 12 laboratory angles from the reaction of 50 MeV 7Li on 56Fe together with evaporative component’s as modeled by CASCADE and fitted to the backward angle data. The deuteron and triton “break-up” spectra obtained by subtracting the evaporative components from the measured spectra are also presented. The break-up of the 7Li projectile near the surface occurs with high probability and the major fraction of the break-up cross-section is taken by (7Li, α) transfer process. A crude estimate of the fraction of the total cross-section is found to be of the same order of magnitude as the overall spectroscopic factor determined by the diffraction model. The value of the estimated fraction of total cross section at 50 MeV incident energy is compared to that at 68 MeV incident energy for the same reaction. However, these values of estimated fraction of total cross section are found very much consistent with the measured yields at both incident energies. The importance of the level density parameter in locating the maximum of excitation energy is indicated in the diffraction model.

A Method of Measuring Hydrogen Isotopes in Surface Layers of Planetary Soils by Spectroscopy of Recoil Protons in Alpha Particle Elastic Scattering

A theoretical and experimental feasibility study of possible determination of the hydrogen and deuterium concentrations in the surface layers of planetary bodies is presented. The method under study is the recoil proton and deuteron spectrometry of forward scattering in the course of elastic interaction of alpha particles with the nuclei of hydrogen isotopes. The spectra of recoil protons and deuterons were recorded using a prototype model of a hydrogen spectrometer, and these spectra were used to determine the hydrogen concentrations in the samples of different compositions.

Analysing spectra on production of light clusters in heavy-ion collisions and reflections on the average phase space density

In the recent past the NA44 Collaboration reported measurements on production of deuteron spectra in SS , SPb and PbPb collisions at the CERN-SPS. This has opened up an avenue, within the confines of the coalescence model, for calculating the source radii of protons, antiprotons and the average phase space densities (APSD) which are being projected, of late, as a reliable observable for studying the freeze-out behaviour of high-energy nuclear collisions. Instead of the thermal or thermodynamical model, we have applied in the present work a set of two models with a new parametrisation which yielded in the past a fair description of some observations on the APSD nature for pion production in nuclear collision. The combination provides here a satisfactory analysis of the p T spectra for both proton and deuteron production and allows us to obtain the values of the hypothesized radii of the assumed spheres of the expansion dynamics and also of the average phase space densities for protons. The values thus arrived at are also quite consistent with the RQMD predictions in the standard literature.

Investigation of K+-meson Production in pA Collisions with ANKE

In a series of measurements with the ANKE spectrometer at COSY-Jülich, the production of K+-mesons in pA (A = C, Cu, Ag and Au) collisions in a wide range of beam energies, Tp = 1.0 ... 2.3 GeV, has been investigated. Double differential cross sections d2σ/dΩdp have been evaluated. The strong suppression in the ratios of K+ production on copper, silver and gold targets to that on carbon observed for pK < 200–250 MeV/c may be ascribed to a combination of Coulomb and nuclear repulsion in the K+A system. Our data are consistent with a K+A nuclear potential of VK0 ≈ 20 MeV at low kaon momenta and normal nuclear density. First momentum spectra of protons and deuterons measured in coincidence with the K+-mesons have been obtained at Tp = 1.2 GeV. These data supply direct evidence for the two-step reaction mechanism, with formation of intermediate pions, leading to kaon production.

100Mo( [formula omitted]) 99Mo reaction at 21 MeV and direct reaction analysis of the low-lying continuum spectrum

The 100Mo( p → ,d ) 99Mo reaction has been studied with 21 MeV polarized protons. Momentum spectra of the emitted deuterons corresponding to the excitation energy region up to 5.75 MeV in 99Mo have been measured. Theoretical analysis based on the standard distorted-wave Born approximation (DWBA) provides the lj-angular momentum transfers and spectroscopic factors of neutron hole states for 27 levels from the ground state up to E X =2.921 MeV. The polarization data gave a more affirmative information in assigning the spins and parities. Spectrum regions from discrete levels to continuum were treated with a global analysis using the direct reaction model and continuous strength functions. The double differential cross section-energy spectra were reproduced fairly well using the DWBA-based cross sections and the asymmetrical Lorentzian form strength response function having energy-dependent spreading widths.

Study of Proton and Deuteron Spectra from Proton Induced Reactions at Intermediate Energies

Intermediate-energy nucleon-nucleus interactions were investigated in order to achieve a more comprehensive understanding of spallation reaction and heavier fragments productions. Measurements of proton and deuteron production reactions for 300- and 392 MeV proton incidence were carried out at RCNP ring-cyclotron facility. Inclusive 12C(p, p′x) and 12C(p, dx) spectra at 300 MeV were measured in a wide energy range and compared with two theoretical calculations: the quantum molecular dynamics model and the intranuclear cascade model. The calculations of the INC model were in good agreement with the experimental results in the quasifree region. The deuteron production cross sections calculated by the QMD model were much smaller than the ones obtained by the measurement. The cause of this discrepancy was discussed in terms of a deuteron knockout process.

Enantiomeric and Enantiotopic Analysis of Cone-Shaped Compounds withC3andC3vSymmetry Using NMR Spectroscopy in Chiral Anisotropic Solvents

We describe the enantiomeric and enantiotopic analysis of the NMR spectra of compounds derived from the functionalized cone-shaped core, cyclotriveratrylenes (CTV), dissolved in weakly oriented lyotropic chiral liquid crystals (CLCs) based on organic solutions of poly-gamma-benzyl-L-glutamate. The CTV core lacks prostereogenic as well as stereogenic tetrahedral centers. However, depending on the pattern of substitution, chiral and achiral compounds with different symmetries can be obtained. Thus, symmetrically nonasubstituted CTVs (C(3) symmetry) are optically active and exhibit enantiomeric isomers, while symmetrically hexasubstituted (C(3v) symmetry) derivatives are prochiral and possess enantiotopic elements. In the first part we use (2)H and (13)C NMR to study two nonasubstituted (-OH or -OCH(3)) CTVs, where the ring methylenes are fully deuterated, and show for the first time that the observation of enantiomeric discrimination of chiral molecules with a 3-fold symmetry axis is possible in a CLC. It is argued that this discrimination reflects different orientational ordering of the M and P isomers, rather than specific chiral short-range solvent-solute interactions that may affect differently the magnetic parameters of the enantiomers or even their geometry. In the second part we present similar measurements on hexasubstituted CTV with flexible side groups (-OC(O)CH(3) and the, partially deuterated bidentate, -OCH(2)CH(2)O-), having on the average C(3v) symmetry. No spectral discrimination of enantiotopic sites was detected for the -OC(O)CH(3) derivative. This is consistent with a recent theoretical work (J. Chem. Phys. 1999, 111, 6890) that indicates that in C(3v) molecules no chiral discrimination between enantiotopic elements, based on ordering, is possible. In contrast, a clear splitting was observed in the (2)H spectra of the enantiotopic deuterons of the side groups in the tri(dioxyethylene)-CTV. It is argued that this discrimination reflects different ordering characteristics of the various, rapidly (on the NMR time scale) interconverting conformers of this compound. Assuming two twisted structures for each of the dioxyethylene side groups, four different conformers are expected, comprising two sets of enantiomeric pairs with, respectively, C(3) and C(1) symmetries. Differential ordering and/or fractional population imbalance of these enantiomeric pairs leads to the observed spectral discrimination of sites in the side chains that on average form enantiotopic pairs.

Progress of fast ignitor studies and Petawatt laser construction at Osaka University

100 TW light from the Petawatt Module (PWM) laser illuminated a preimploded spherical deuterated polystyrene(CD) shell target. The DD neutron yield increased from 2.5×105–106. Analysis indicates that hundreds of keV deuterons, generated around the critical density, collide with cold fuel deuterons and play the leading role in the enhancement of the neutron yield. A two-dimensional particle-in-cell (2D PIC) simulation predicted well the deuteron spectrum. A 60 TW laser was used for MeV proton emissions and megagauss magnetic fields generation on the rear surface of a Poly p-xylene(C8H8) plane target. The 2D PIC simulation explained well the results. The PWM laser was upgraded to one PW, making it the world biggest Petawatt laser (PW laser). An optically parametric chirped amplification was introduced in the front end. The pulse was synchronized to the GEKKO XII imploding beams to within 10 ps.

β-delayed deuteron emission from6He

The \ensuremath{\beta} delayed deuteron decay of ${}^{6}\mathrm{He}$ has been measured at the TISOL facility at TRIUMF. For the \ensuremath{\beta}-particle measurement a silicon-germanium telescope array has been used. To separate deuterons from $\ensuremath{\alpha}$ particles and to obtain the spectral form of the deuteron decay, a $d\ensuremath{-}\ensuremath{\alpha}$ coincidence technique has been employed using two opposite silicon detectors. The \ensuremath{\beta} branch has been determined from the geometry of the experiment and also by comparison with the well-known $\ensuremath{\beta}\ensuremath{-}\ensuremath{\alpha}$ decay modes of ${}^{16}\mathrm{N}$ and ${}^{8}\mathrm{Li}.$ A branching ratio of $(1.8\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ above the $\ensuremath{\beta}$ cutoff (350-keV deuteron laboratory energy) and $(2.6\ifmmode\pm\else\textpm\fi{}1.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ for the entire spectrum has been determined for this decay. In the course of the measurement the half-life of ${}^{6}\mathrm{He}$ has been remeasured to be ${T}_{1/2}=0.810\ifmmode\pm\else\textpm\fi{}0.008 \mathrm{s}.$ High statistical accuracy in the deuteron spectrum has been obtained that allowed a comparison of the shape of the deuteron spectrum to theoretical predictions.

Low-Ktwo-quasiparticle states in180Ta

Excited states in ${}^{180}\mathrm{Ta},$ populated in the ${}^{180}\mathrm{Hf}(p,n)$ and $(d,2n)$ reactions, were investigated by in-beam $\ensuremath{\gamma}$-ray and conversion-electron spectroscopy. In addition to the excited two-quasiparticle bands with ${K}^{\ensuremath{\pi}}{=0}^{\ensuremath{-}}$ and ${1}^{\ensuremath{-}}$ known from previous work, we have identified six other low-lying two-quasiparticle bands with $K&lt;~4.$ At intermediate K, 12 previously unkown levels were identified that could, however, not be associated reliably with rotational bands. These levels might be of significance in connection with the as yet unresolved problem of the stellar production mechanism for the ${9}^{\ensuremath{-}}$ isomer of ${}^{180}\mathrm{Ta}.$ At higher K we observe only levels known from the previous in-beam $\ensuremath{\gamma}$-spectroscopic studies with heavier projectiles, but suggest for some levels a different ordering into rotational bands based on band-mixing considerations. We also report a deuteron spectrum measured in the ${}^{181}\mathrm{Ta}{(p,d)}^{180}\mathrm{Ta}$ reaction with high resolution and statistics. This spectrum served for configuration assignments and yields an energy of $78\ifmmode\pm\else\textpm\fi{}1 \mathrm{keV}$ for the ${9}^{\ensuremath{-}}$ isomer in ${}^{180}\mathrm{Ta}.$

Complete and incomplete fusion in reactions of 7Li + 56Fe at E(7Li) = 50 and 68 MeV from analysis of recoil range and light-particle measurements

Excitation functions for the production of eight radioactive products of the reactions of 7Li on 56Fe have been measured up to E(7Li) = 89 MeV. Recoil range distributions for these products, together with inclusive proton, deuteron, triton and alpha spectra, have been measured at energies of 50 and 68 MeV. The α, t and d spectra show characteristic “break-up” components at forward angles, while the recoil distributions show evidence of complete fusion and incomplete-fusion process 56Fe( 7Li,α) 59Co * . A parallel study on 55Mn shows some evidences of the ( 7Li,t) incomplete-fusion process, but the cross-section for this process is significantly less than for the triton fusion process. The recoil distributions can be reproduced on the assumption that essentially all the observed break-up fragments are in fact associated with incomplete fusion, but uncertainties in normalisation leave open the possibility of a significant contribution of pure break-up. A diffraction model of the ( 7Li,α) transfer process reproduces the observed break-up α spectra with some success.

Study of direct-drive, deuterium–tritium gas-filled plastic capsule implosions using nuclear diagnostics at OMEGA

Implosions of direct-drive, deuterium–tritium (DT) gas-filled plastic capsules are studied using nuclear diagnostics at the OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. In addition to traditional neutron measurements, comprehensive sets of spectra of deuterons, tritons, and protons elastically scattered from the fuel and shell by primary DT neutrons (“knock-on” particles) are, for the first time, obtained and used for characterizing target performance. It is shown with these measurements that, for 15-atm DT capsules with 20-μm CH shells, improvement of target performance is achieved when on-target irradiation nonuniformity is reduced. Specifically, with a two-dimensional (2D) single-color-cycle, 1-THz-bandwidth smoothing by spectral dispersion (SSD), plus polarization smoothing (PS), a primary neutron yield of ∼1×1013, a fuel areal density of ∼15 mg/cm2, and a shell areal density of ∼60 mg/cm2 are obtained; these are, respectively, ∼80%, ∼60%, and ∼35% higher than those achieved using 0.35-THz, 3-color-cycle, 2D SSD without PS. (In determining fuel areal density we assume the fuel to have equal numbers of D and T.) With full beam smoothing, implosions with moderate radial convergence (∼10–15) are shown to have ρR performance close to one-dimensional-code predictions, but a ratio of measured-to-predicted primary neutron yield of ∼0.3. Other capsules that are predicted to have much higher radial convergence (3.8-atm DT gas with 20-μm CH shell) are shown to have ρRfuel∼3 mg/cm2, falling short of prediction by about a factor of 5. The corresponding convergence ratios are similar to the values for 15-atm capsules. This indicates, not surprisingly, that the effects of mix are more deleterious for high-convergence implosions. A brief comparison of these moderate- and high-convergence implosions to those of similar deuterium–deuterium (D2) gas-filled capsules shows comparable hydrodynamic performance.

(Anti)proton and pion source sizes and phase space densities in heavy ion collisions

NA44 has measured mid-rapidity deuteron spectra from AA collisions at sqrt{s}=18GeV/A at the CERN SPS. Combining these spectra with published proton, antiproton and antideuteron data allows us to calculate, within a coalescence framework, proton and antiproton source sizes and phase space densities. These results are compared to pion source sizes and densities, pA results and to lower energy (AGS) data. The antiproton source is larger than the proton source at sqrt{s}=18GeV/A. The phase space densities of pions and protons are not constant but grow with system size. Both pi+ and proton radii decrease with transverse mass and increase with sqrt{s}. Pions and protons do not freeze-out independently. The nature of their interaction changes as sqrt{s}, and the pion/proton ratio increases.