Radiative Deuteron Capture Research Articles

Radiative 2H3He Capture at Low Energies

The results are presented on the total cross sections, astrophysical S-factor, reaction rate of the deuteron radiative capture on 3He at the temperatures from 0.03 up to 3 T9 calculated in the framework of the potential cluster model with the forbidden states coming from the classification of the orbital states by the Young diagrams. Within the used model and exploited Young diagram classification made it possible to reproduce the general features of the available experimental data on the cross section and reconstructed astrophysical S-factor in the energy range from 200 keV up to 1.4 MeV. The parametrization of the obtained reaction rate has been found and been compared with some other actual reactions with light clusters.

Modern Chiral Forces Applied to the Nucleon\u2013Deuteron Radiative Capture

The chiral nucleon–nucleon interaction with semi-local regularization up to the fifth order of chiral expansion is applied to the nucleon–deuteron radiative capture process. Our theoretical approach is based on the formalism of Faddeev equations and the Siegert theorem is exploited to construct the electromagnetic current operator. The very weak dependence of the differential cross section on values of the regularization parameter is observed. This suggests that the improved chiral two-body interaction is a promising starting point to study electromagnetic processes at low energies.

The Photon Polarization Parameter of 2H(n, γ)3H reaction with Inclusion of the Electric Quadrupole Contribution

We use effective field theory (EFT) for the calculation of neutron—deuteron radiative capture at very low energies. We present here the use of EFT to calculate a low-energy photo-nuclear observable in three-body systems, the photon polarization parameter and fore—aft asymmetry at thermal neutron energies up to next-to-next to leading order (N2LO), with inclusion of the electric quadrupole contribution. The photon polarization parameter in total is found to be Rc = −0.421 ± 0.003 and is in good agreement with the other modern theoretical calculations based on modern nucleon—nucleon potentials. In comparison with our previous work, a satisfactory agreement with the available experimental data is found by inclusion of the electric quadrupole contribution.

TRITON BREAKUP AND FORMATION AT VERY LOW ENERGIES

Different theoretical models for two- and three-body electromagnetic currents are constructed using meson-exchange mechanisms and minimal substitution in the momentum dependence of two- and three-nucleon interactions. We review the use of effective field theory (EFT) to compute electromagnetic reactions in three-nucleon systems at very low energies. We first explain how EFT theory can be extended to incorporate the photon into the three-nucleon systems when also a three-nucleon force is acting. We also explain the predictions of the resulting EFT for neutron–deuteron radiative capture process at very low energies. In this work, a number of low-energy photonuclear observables, including neutron–deuteron radiative capture reactions and triton photodisintegration, are calculated in order to make a comparative study of the pion-less EFT results with the models based on the realistic Argonne v18(AV18) two-nucleon and Urbana IX or Tucson–Melbourne three-nucleon interactions. The calculated cross-section of neutron–deuteron radiative capture and photon polarization parameter of 3 H are in satisfactory agreement with the available experimental data.

Experimental search for the radiative capture reaction d + d → 4He + γ from the ddμ muonic molecule state J = 1

A search for the muon-catalyzed fusion reaction d + d → 4He + γ in the ddμ muonic molecule was performed using the experimental installation TRITON with BGO detectors for γ-quanta. A high-pressure target filled with deuterium was exposed to the negative muon beam of the JINR Phasotron to detect γ-quanta with the energy 23.8 MeV. An experimental estimation for the yield of radiative deuteron capture from the ddμ state J = 1 was obtained at the level of ηγ ≤ 8 × 10−7 per fusion.

Formula omitted] with effective field theory

The cross section of neutron–deuteron radiative capture n d → H 3 γ is calculated at energies relevant to big-bang nucleosynthesis ( 20 ⩽ E ⩽ 200 keV ) with pionless effective field theory. At these energies, magnetic transition M1 gives the dominant contribution. The M1 amplitude is calculated up to next-to-next-to leading order (N 2LO) with insertion of three-body force. Results are in good agreement within few percent theoretical uncertainty in comparison with available calculated data below E = 200 keV .

Search for the radiative capture reaction d+d → 4He+γ from the ddμ muonic molecule state

A search for the muon catalyzed fusion reaction dd --> ^4He +\gamma in the dd\mu muonic molecule was performed using the experimental \mu CF installation TRITON and NaI(Tl) detectors for \gamma-quanta. The high pressure target filled with deuterium at temperatures from 85 K to 800 K was exposed to the negative muon beam of the JINR phasotron to detect \gamma-quanta with energy 23.8 MeV. The first experimental estimation for the yield of the radiative deuteron capture from the dd\mu state J=1 was obtained at the level n_{\gamma}\leq 2\times 10^{-5} per one fusion.

Faddeev calculations of proton–deuteron radiative capture with π- and ρ-meson exchange currents of the Argonne potentials

Faddeev calculations of proton–deuteron radiative capture with π- and ρ-meson exchange currents of the Argonne potentials

Coulomb polarizability of the deuteron and the E1 capture mechanism in the 4He(d, gamma )6Li reaction.

The $^{4}\mathrm{He}$ (d,\ensuremath{\gamma}${)}^{6}$Li reaction, which proceeds through the overwhelming E2 transition, but with a small admixture of the E1 transition, is a possible mechanism for the $^{6}\mathrm{Li}$ nucleosynthesis in the Big Bang. The E1 radiation is, however, strongly suppressed in the radiative deuteron capture reaction in self-conjugate nuclei. Usually, the observed small, but not negligible, E1 radiation has been attributed to the spin-dependent electric dipole operator. In this study it is shown how the Coulomb polarization of the deuteron $^{4}\mathrm{He}$(d,\ensuremath{\gamma}${)}^{6}$Li reaction. Expressly we investigate the E1 capture process which proceeds with a small change of the deuteron internal structure in the entrance channel state. The structural change of the deuteron is engendered by the Coulomb field in the system of target and deuteron and such a deviant deuteron state is surveyed by calculating the expectation value of the relative coordinate between the proton and neutron in the deuteron. We then show how the electrically polarized deuteron state releases the usual E1 selection rule, and subsequently we calculate the relative intensity of the E1 versus E2 radiation in the $^{4}\mathrm{He}$(d,\ensuremath{\gamma}${)}^{6}$Li reaction.

Gamma ray to charged particle branching ratios for the radiative capture of deuterons by 2H, 6Li, and 10B

The gamma to charged particle branching ratios for the radiative capture reactions of deuterons by 2H, 6Li, and 10B have been measured between center of mass energies of 20 and 40 keV, 80 and 110 keV, and 150 and 170 keV, respectively. The branching ratios for these very high-energy gamma rays, having values of 23.8, 22.3, and 25.2 MeV for the targets 2H, 6Li, and 10B, respectively, constitutes the data base for the gamma ray diagnostics of the corresponding fusion plasmas. For the fusion gamma ray detector on TFTR, counting rates for these gamma rays as a function of the total fusion reaction rate will be presented.

Proton and deuteron radiative capture to A = 13 nuclei

Differential capture 12C(p, γ) 13N and 11B(d, γ) 13C cross sections have been measured in the excitation energy region between 20 and 45 MeV in 13N and 25 and 42 MeV in 13C. Angular distributions are given for the pγ channel at each energy, while the dγ excitation function has been measured at 60°. The pγ 0 data show, besides a direct capture term, the excitation of giant dipole resonances based on excited states of the compound nucleus. The main feature of the deuteron capture cross section can be understood in terms of a mechanism in which the proton-neutron pair is captured in the same single particle configuration by the 11B core.

Is it possible to observe an isoscalar E1-multipole in [formula omitted] reactions?

Radiative capture of deuterons by α-particles (αd→ 6Liγ) and the inverse reactions are considered in the framework of the potential cluster model. Special attention is paid to corrections to the E1 multipole in the long wave approximation which can compete with the dominant E2 multipole. It is shown that these corrections could already be detected in the experimental data on the angular distributions of photons. The asymmetry of the deuteron angular distributions in polarized γ-quanta disintegration could be another quantity where the E1 transition could be exhibited. Among many corrections, the one which is due to the mass difference between the α-particle and two times the deuteron mass is the most important.

Proton and deuteron radiative capture in light nuclei

Differential capture 16 O( p, γ x) 17 F and 15 N( d, γ x) 17 O cross sections have been measured at excitation energies between 17 and 41 MeV in 17F and 26 and 39 MeV in 17O at several angles in the 35°–135° interval. The (p, γ o) data show, besides a direct capture term, the excitation of giant dipole resonances based on excited states having a probable 2p-1h structure. The main features of the deuteron capture cross section can be understood in terms of a semidirect mechanism with the two nucleons captured in the same single-particle configuration.

Radiative capture of deuterons in Ba and Au

138Ba(d,γ)140La and197Au(d,γ)199mHg cross sections were measured for deuteron energies ranging from 5 to 26 MeV. A survey of existing experimental (p,γ), (d,γ) and (α,γ) cross sections is given. A comparison of all the experimental data with calculated compound nucleus cross sections is performed. An increase in the ratio of experimental cross sections and calculated compound nuclear cross sections with increasing mass numberA is observed for all capture processes.

Evidence for aT=12Resonance in theHe3System

Evidence for a broad resonance in the $^{3}\mathrm{He}$ system has been found in the excitation function for the radiative capture of deuterons by protons. Supporting evidence is provided by the behavior of the angular distributions. The resonance is centered at (19.5\ifmmode\pm\else\textpm\fi{}0.5)-MeV excitation, has a width of about 2 MeV, and is most likely characterized by $({L}^{\ensuremath{\pi}},S,T)=({1}^{\ensuremath{-}},\frac{1}{2},\frac{1}{2})$.

Radiative Capture of Deuterons by Protons

The differential cross section for radiative capture of deuterons by protons has been measured by a novel method at deuteron energies near 20 and 30 MeV. The angular distributions are sufficiently detailed to show effects of transitions higher than quadrupole. The total cross sections, which are accurate to \ifmmode\pm\else\textpm\fi{}7%, are about 10% below recent theoretical calculations.

Radiative capture mechanisms in heavy nuclei

The known cross section data for radiative capture in heavy nuclei of 5–50 MeV nucleons and composite projectiles are summarized and the probable reaction mechanisms involved are discussed. Almost all the (α, γ) and (d, γ) results are shown to be in reasonable agreement with statistical theory predictions, especially when corrections for multiple γ-ray cascades and angular momentum effects are included. In particular, the variation of over two orders of magnitude in the reported (α, γ) maximum cross-sections are correctly predicted by statistical theory. To allow for the different nuclear penetrabilities of the various projectiles, each of the experimental capture cross section values has been divided by the appropriate optical model total reaction cross-section. The results provide strong support for the proposal that nucleon capture proceeds predominantly by direct or collective reaction mechanisms. Evidence that non-statistical processes make important contributions in the case of 3He ion capture is also presented. It is concluded that there is no current evidence for mechanisms other than compound nucleos formation and decay in the radiative capture of deuterons and α-particles and that the projectile neutron/proton ratio has a marked effect on the probability of radiative capture.

Capture radiative des deutérons dans la région de la résonance géante de 16O

Radiative capture of deuterons in the giant resonant states in 16O are studied theoretically within the framework of one-particle — one-hole and two-particle — two-hole excitations. The experimental gamma-ray angular distribution, which exhibits an admixture character of dipole and quadropole transitions, is explained by the competition between direct electric quadrupole transition and semi-direct electric dipole transition for which a Coulomb mixture of two isobaric spin states, T = 0 and T′ = 1, is introduced. The calculated total cross-section curves show that the observed radiative dipole capture of deuteron in the giant resonance region is principally due to the isobaric spin impurity of two close dipole states.

Compound-statistical features of deuteron-induced reactions: (I). Radiative capture of 4–15 MeV deuterons

Absolute cross sections and excitation functions for the 30Si(d, γ) 32P and 138Ba(d, γ) 140La reactions from ≈ 4 to 15 MeV have been measured radiochemically using the stacked target technique. The 30Si(d, γ) cross sections above 5 MeV are 110 to 160 μb and exhibit little energy dependence. The 138Ba(d, γ) excitation function peaks at ≈ 22 μb near 10 MeV. The compound nucleus mechanism, formulated from continuum-theory cross sections and statistical-model calculations using Fermi gas level densities, reproduces both the magnitudes and the dissimilar energy dependences of the two excitation functions. Inverse E1 photonuclear cross sections were calculated both for the giant resonance shape used by Carver and Jones and for that proposed by Lane and Lynn, the former providing more satisfactory agreement with experiment, especially in the Si reaction. It is concluded that these radiative deuteron capture reactions can be explained in terms of compound nucleus formation followed by statistical de-excitation.

Study of the inverse photodeuteron reaction in 11B and 16O in the giant resonance energy region

The radiative capture of deuterons by 9Be and 14N has been studied in the energy range 0.5 MeV < E d < 5.5 MeV using direct observation of the ground state gamma transition of about 20 MeV energy. After a short description of the experimental method the results of the measurements are given in the form of excitation curves and angular distributions. For the 9Be(d, γ 0) 11B reaction the excitation curve shows no structure with a total peak cross section of about 8 μb. The results may be interpreted by direct E 1 capture besides the asymmetry of the angular distributions. For the 14N(d, γ 0) 16 O reaction, where the isospin selection rule forbids the E 1 transition, the excitation curve shows a peak at 22.7 MeV excitation energy with a total peak cross section of about 6 μb. The angular distribution at this energy has a predominantly dipole characteristic but also displays asymmetry. The peak cannot be identified with any peak of the giant E 1 resonance of 16O. There are also indications for peaks at 22.2 and 24.5 MeV excitation energy. The possible interpretations for the 14N(d, γ 0) 16O cross section are given.