Deuteron Spectra Research Articles

Calculation of deuteron spectra for nucleon induced reactions on the basıs of the hybrid exciton model taking into account direct processes / Berechnung von Deuteronen-Spektren für nukleoneninduzierte Reaktionen auf der Basis des Hybrid Exciton Model unter Berücksichtigung direkter Prozesse.

Non-equilibrium deuteron spectra have been calculated using a new approach based on the hybrid exciton model for reactions induced by intermediate energy nucleons. The coalescence pick-up model was used to describe the pre-equilibrium deuteron emission. Contribution of the direct processes to deuteron emission was calculated on the basis of a suggested phenomenological approach.

Beta decay of 11Li to the deuteron channel and halo analog states in 11Be.

States in the $^{11}\mathrm{Be}$ spectrum, termed halo analog (HA) states, with halo isospin ${\mathit{T}}^{\mathit{h}}$=1, 0 are studied in the framework of a three-body ${(}^{9}$Li+n+p) approach and a microscopic hyperspherical harmonics method. Three-body bound and scattering (HA) states, with structure similar to the two-neutron halo state of $^{11}\mathrm{Li}$, are obtained in $^{11}\mathrm{Be}$ at the excitation energies above 18 MeV and compared with experimental spectra. The influence of the ``deuteronlike'' halo analog state with T=3/2 (${\mathit{T}}^{\mathit{h}}$=0) on \ensuremath{\beta}-delayed deuteron emission from $^{11}\mathrm{Li}$ is studied. It is found that the shape of the deuteron spectrum and branching ratio to the $^{9}\mathrm{Li}$+d channel are sensitive to the position of this halo analog state in $^{11}\mathrm{Be}$.

Synchrotron radiation excitation of hydrogen and deuterium to superexcited states

The kinetic energy spectra of fragment protons and deuterons produced in the dissociative photoionization of hydrogen and deuterium by 27.5–37.5 eV photons have been measured. Measurements were made both along and at right angles to the E vector of the synchrotron radiation to isolate the Q 1 and Q 2 superexcited states of Σ and Π symmetry. It is shown that the results can provide, for the first time, an experimental estimate of the autoionizing state widths of these superexcited states as a function of internuclear separation, R. The experimentally determined state widths are significantly larger than theoretical predictions, especially at large R. Furthermore, there is an unexpectedly large isotope effect.

Measurements of the secondary particle energy spectra in the space shuttle

Measurements of the energy spectra of secondary particles produced by galactic cosmic rays and trapped protons due to the nuclear interactions of these particles with the Shuttle shielding provide a powerful tool for validating radiation transport codes. A code validated in this way can be used to better estimate the dose and dose equivalent to body organs, measurements that cannot be made directly. The principal cause of single event upsets in electronic devices in the region of the South Atlantic Anomaly is secondary particles, and even in the region of galactic cosmic radiation a significant fraction is produced by secondary particles. In this paper, we describe the first direct measurements of the energy spectra of secondary protons, deuterons, tritons, 3He and 4He produced by galactic cosmic rays inside the Space Shuttle using a charged particle spectrometer. A comparison of these spectra with radiation transport code HZETRN showed reasonably good agreement for secondary protons. However, the code seriously underestimated the flux of all other light ions. The code has been modified to include pick-up and knock-on processes. The modified code leads to good agreement for deuterons and 3He but not for other light ions. This revised code leads to about 10% higher dose equivalent than the original code under moderate shielding, if we assume that higher charge ion fluxes are correctly predicted by the model.

Multinucleon effects in muon capture on 3He at high energy transfer.

Energy spectra of both protons and deuterons emitted following the capture of negative muons by [sup 3]He nuclei have been measured for energies above 15 MeV. A limited number of proton-neutron pairs emitted in coincidence were also observed. A simple plane wave impulse approximation (PWIA) model calculation yields fair agreement with the measured proton energy spectra, but underpredicts the measured rate of deuteron production above our energy threshold by a large factor. A more sophisticated PWIA calculation for the two-body breakup channel, based on a realistic three-body wave function for the initial state, is closer to the deuteron data at moderate energies, but still is significantly lower near the kinematic end point. The proton-neutron coincidence data also point to the presence of significant strength involving more than one nucleon in the capture process at high energy transfer. These results indicate that additional terms in the capture matrix element beyond the impulse approximation contribution may be required to explain the experimental data. Specifically, the inclusion of nucleon-nucleon correlations in the initial or final state and meson exchange current contributions could bring calculations into better agreement with our data. A fully microscopic calculation would thus open the possibility for a quantitative testmore » of multinucleon effects in the weak interaction.« less

A test of K-matrix formulae

Abstract R -matrix and K -matrix fits to elastic scattering and reaction data involving low-lying 0 + states of 8 Be are compared. Three-level R -matrix formulae give good simultaneous fits to the ground-state energy and width, the α + α s-wave phase shift and a 9 Be(p, d) 8 Be deuteron spectrum that shows the 8 Be ground-state ghost. The values of the α + αf channel radius are reasonable (about 6 fm), and the third level representing the background lies above the energy range being fitted. The corresponding K -matrix formulae, with a background level lying above the fitted energy range, cannot give good fits to the same data. It seems necessary to introduce an echo pole just below the 8 Be ground state, and then the data can be well fitted. Inclusion of such a pole means, however, that 8 Be ground-state properties are not well determined by extrapolation of the high-energy data alone. It therefore seems that K -matrix formulae should be used with caution in other cases where high-energy data are extrapolated to the low energies of interest in astrophysics.

Microscopic description of the beta delayed deuteron emission from 6He.

The beta delayed deuteron emission from $^{6}\mathrm{He}$ is studied in a dynamical microscopic cluster model. This model gives a reasonably good description for all the subsystems of $^{6}\mathrm{He}$ and $^{6}\mathrm{Li}$ in a coherent way, without any free parameter. The beta decay transition probability to the $^{6}\mathrm{Li}$ ground state is underestimated by a few percent. The theoretical beta delayed deuteron spectrum is close to experiment but it is also underestimated, by about a factor of 1.7. We argue that, in spite of their different magnitudes, both underestimations might have a common origin. The model confirms that the neutron halo part of the $^{6}\mathrm{He}$ wave function plays a crucial role in quenching the beta decay toward the \ensuremath{\alpha}+d channel.

Production of light particles after antiproton-nucleus annihilation and their interpretation with statistical models

Energy spectra of protons, deuterons and tritons from stopped-antiproton annihilation in Li, Si, Ca, Ni, Ge, Mo, Ho, Yb, Pb and Th have been measured with a Ge detector telescope. The shapes of these and of previously obtained spectra and the corresponding yields were analysed and compared with statistical calculations including intranuclear cascade, coalescence, pre-equilibrium processes, evaporation, multifragmentation and Fermi break-up. The relative importance and the A-dependence of the various processes are elucidated.

Spectra and multiplicities of n, p, d, t, K±, π± from antiproton annihilation in Cu and U

Inclusive energy spectra of neutrons, protons, deuterons, tritons, charged kaons and pions following antiproton annihilation at rest in copper and uranium have been measured. The determined multiplicity charged kaons is compared to recent measurements and indicates an enhancement of strangeness production. Ratios of directly emitted neutrons and protons have been determined for copper and uranium to 3.0±0.6 and 3.2±0.5, respectively.

Light particle emission in Boltzmann master equation theory of pre-equilibrium reactions.

A method is proposed to account for the emission of light particles in heavy-ion fusion reactions using the Boltzmann master equation approach. The method consists in a simple phase space calculation which allows one to estimate the formation probability of a cluster for a given energy distribution of the nucleons. The emission probability of the clusters at each stage of the equilibration cascade is calculated and the changes of the occupation probabilities of the nucleon energy states due to these emissions is accounted for by a new depletion term in the set of master equations. The calculated spectra of deuterons, tritons, and \ensuremath{\alpha} particles reproduce satisfactorily the exclusive spectra measured in $^{16}\mathrm{\ensuremath{-}}$ and $^{32}\mathrm{Ag}$ fusion at 30 MeV/nucleon incident energy. The same model is used to predict the emission of clusters in nucleon-induced reactions with satisfactory results.

Accelerated deuterons in cluster-fusion experiments.

The collisional interaction of heavy-water clusters with TiD has been studied theoretically via three independent methods with the aim of estimating cluster-fusion yields. Particular attention was paid to multiple wide-angle-scattering processes between deuterons and heavy beam or target atoms. In order to achieve adequate statistics in molecular-dynamics simulations, the elastic-scattering cross section was enhanced by, roughly, increasing the deuteron charge at constant mass. Deuteron spectra were then determined by extrapolation to Z=1. The validity of the procedure was confirmed by comparison with simulations using unscaled interaction potentials. Monte Carlo simulations were also performed, using a code that incorporates target motion and allows for larger cluster and target size. Cross sections for double wide-angle-scattering events (Fermi shuttles) were computed directly. By all three methods we find clear evidence that deuterons are accelerated far beyond the limits imposed by single-scattering kinematics. We find exponential tails with slopes approximately inversely proportional to the incident energy per cluster atom. Estimated fusion yields increase very strongly with the energy per beam atom and lie 8 to 18 orders of magnitude below those reported experimentally.

Charged-particle evaporation from hot composite nuclei: Evidence over a broad Z range for distortions from cold nuclear profiles.

Charged-particle emission has been studied in ten heavy-ion reactions spanning composite systems of 16\ensuremath{\le}Z\ensuremath{\le}64. By means of reversed kinematics, high-quality energy spectra were obtained for proton and alpha evaporation from compound nuclei with temperatures \ensuremath{\sim}1.5--3.5 MeV and spins up to \ensuremath{\sim}70\ensuremath{\Elzxh}. In some cases, deuteron and triton spectra were recorded as well. Statistical model calculations for spherical nuclei require systematically low emission barriers to reproduce the data. For the lighter systems, the effective spins (or moments of inertia) must be modified as well, whereas for the heavier systems this effect is of less importance. The roles of multistep particle emission and competition in the model calculations are assessed and found to be inadequate to explain the observed discrepancies. Calculations that model statically deformed nuclear emitters suggest that large deformations may be present, but they do not give a satisfactory overall picture. The very low proton energies in particular seem to indicate an extended density profile. Such an effect, together with the requirements for cluster preformation, may explain the observed low barriers for $^{1}\mathrm{H}$${/}^{4}$He and the increasing mean energies found for the series $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, $^{3}\mathrm{H}$, respectively.

Deuteron production in alpha -nucleus collisions from 200 to 800 MeV per nucleon.

Deuteron spectra at laboratory angles from 30\ifmmode^\circ\else\textdegree\fi{} to 90\ifmmode^\circ\else\textdegree\fi{} were measured in \ensuremath{\alpha}+(Pb, Cu, and C) collisions at 800, 600, and 200 MeV/nucleon, and \ensuremath{\alpha}+(Pb and C) collisions at 400 MeV/nucleon. The coalescence relation between protons and deuterons was examined for the inclusive part of the spectra. The size of the interacting region was evaluated from the observed coalescence coefficients. The rms radius is typically 4--5 fm, depending of the target mass. The proton and deuteron energy spectra corresponding to central collisions were fitted assuming emission from a single source moving with a velocity intermediate between that of the projectile and the target. The extracted ``temperatures'' are independent of the nature of the emitted particle, indicating that the fragments have a common source. The best fits were achieved for 200- and 400-MeV/nucleon reactions. Spectra of deuteron-like pairs, including real deuterons and neutron-proton pairs that may be contained in a larger nuclear cluster, are compared to the prediction of an intranuclear cascade model incorporating a clustering algorithm based on a classical coalescence prescription. Best agreements between experimental and predicted deuteron-like spectra occur for 800- and 600-MeV/nucleon collisions.

The configuration and the dynamics of the -CD3groups in methyl deuterated dimethylmalonic acid

The angular variation of the deuteron NMR of single crystals of methyl deuterated dimethylmalonic acid, C(CD3)2(COOH)2 (DMMA), was measured at room temperature and at 56 K. From the room temperature data the motionally averaged deuteron quadrupole coupling tensors for rapidly reorienting methyl groups are determined. The C-Cmethyl bond directions are inferred from the unique principal axes of these tensors. A semi-quantitative analysis of the 56 K data leads to the conclusion that at this temperature the methyl groups are immobile and that the configuration of the two methyl groups within the DMMA molecule is an eclipsed one. By line shape analysis of deuteron spectra recorded for 290 K > T > 60 K the Arrhenius parameters for reorienting -CD3 groups E a = 9·5 kJ mol-1 and k (D) 0 = 0·8 × 1011 s-1 were determined. No features giving evidence for tunnelling could be observed in the low temperature deuteron spectra. An upper limit of 3 kHz is derived for the -CD3 tunnel frequency v (D) t for T → 0.

Competition between multiphoton fragmentation channels in H2 and HD induced by intermediate states.

The proton and deuteron spectra following resonant multiphoton ionization of H 2 and HD at 193 nm through the E, F state have been studied at power densities of 10 10 W/cm 2 . Our results show that the intermediate state induces competition between 3(2+1)-photon ionization, dissociation, and dissociative ionization channels. We find that the competition depends on the specific vibrational and rotational levels excited in the intermediate state

Charged-particle spectra from antiproton annihilation at rest in a = 12–238 nuclei

Energy spectra of protons, deuterons and tritons from the annihilation of antiprotons stopped in 12C, 40Ca, 63Cu, 92,98Mo and 238U have been measured with a Ge-detector telescope. Parameters related to the shape of the spectra were calculated and their dependence on target and ejectile mass number was determined. Yields per p̄ of directly emitted protons, deuterons and tritons and of evaporated protons were estimated.

The27Al(n, d)26Mg reaction at 22 MeV

Deuteron spectra from the reaction27Al(n, d)26Mg has been measured at reaction angles 0°→60°, with a spectrometer comprising three multiwire proportional counters followed by a curved plastic scintillator. Spectra were obtained with an energy resolution of ∼0.7 MeV and an angle resolution of ∼5°. Angular distributions for transitions to the ground state and excited states at 1.81, 2.93 and 4.3 MeV in26Mg were obtained. Distorted waves analysis of the angular distributions yield spectroscopic factors of 0.29(8), 0.9(3), 0.18(7) and 1.9(6) for the ground and excited states, respectively. The results are compared with previous (d,3He) and (n, d) measurements, and with theoretical predictions.

Charged-particle spectra from antiproton annihilation at rest in = 12–238 nuclei

Energy spectra of protons, deuterons and tritons from the annihilation of antiprotons stopped in 12 C, 40 Ca, 63 Cu, 92,98 Mo and 238 U have been measured with a Ge-detector telescope. Parameters related to the shape of the spectra were calculated and their dependence on target and ejectile mass number was determined. Yields per p̄ of directly emitted protons, deuterons and tritons and of evaporated protons were estimated.

Analysis of deuteron spectra from hadron-nucleus reactions at several GeV/c with the coalescence model

Spectra of protons and deuterons emitted in hadron-nucleus reactions at 4 GeV/ c were studied with the coalescence model to deduce information on the spatial extent of the emission source. The source sizes correlated strongly to nucleon multiplicities, and indirectly to the target mass and the associated pion multiplicity. Theanalysis indicated the formation of a slow moving source previously assumed in the two-moving-source parametrization.

Systematics of coalescence radii for light-fragment emission from energetic heavy-ion collisions

The refined coalescence model has been applied to the analysis of triton and helion (3He) spectra from various heavy-ion colliding systems atE inc/A∼(15÷25) MeV/nucleon. The results show that the obtained coalescence radii increase with increasing asymmetry of the colliding system. A similar trend was observed previously for alpha and deuteron spectra.