Structure en bande du noyau 22Na: Le premier niveau Jπ = 6+

We investigate the two-body photodisintegration of ³He and its inverse, radiative p-d capture using bound-state functions corresponding to the N-N interaction being given by the Reid soft-core potential. For the two-body photodisintegration of ³He Coulomb effects and the final-state interactions between the proton and deuteron are not included. At low energy the shape of the angular distribution agrees well with experiment, but the 90° cross section exhibits an anomalous peak at 15 MeV due to electric dipole transitions connecting the deuteron and ³He D-states. The low-energy cross section is 25–40 % too small. The intermediate-energy angular distribution peaks too near the forward direction, and, contrary to experiment, has a minimum at 100°. At higher energy the 90° cross section in the center-of-momentum frame is at least an order of magnitude too small, but does display the correct energy dependence. This energy dependence is related to the properties of the bound-state wave functions and it is plausible that it will persist in an improved treatment (e.g. one which includes exchange currents) which properly accounts for the magnitude of the cross section. Contributions from the ³He S-states are negligible for photon energies between 100 and 150 MeV, but are dominant outside this energy region.     

The two-body photodisintegration of the 3He nucleus

The two-body photodisintegration of ³He is calculated using ³He and proton-deuteron wave functions obtained by assuming a separable interaction for the two-nucleon t-matrix. We show that the isotropic component of the cross section is unlikely to yield useful information on the D-state probability densities of the deuteron and ³He. A detailed comparison is made with the data on the cross section at 90°. The separable approximation can account for some of the experimental results, but other experiments suggest that a more sophisticated treatment of the nuclear interactions and wave functions is necessary.     

Electromagnetic processes in light nuclei: Results within a microscopic approach

Results obtained by investigating the electrodisintegration of A = 3 and 4 nuclei and the photodisintegration of A = 3, 4, 6, and 7 nuclei on the basis of precise solutions to dynamical problems involving NN and NNN forces are presented. The role of NNN forces, final-state relativistic effects, the contribution of meson-exchange currents, an anomaly in electrodisintegration at high momentum transfers and low energy transfers, sensitivity to nuclear dynamics in the exclusive electrodisintegration of ⁴He nuclei, and the soft-mode resonance in the photodisintegration of ⁶He nuclei are considered.     

Baryon resonances of the proton and few-body systems in the 200–800 MeV energy range

The total photoabsorption cross sections for ¹H, ²H, ³He, and ⁴H have been measured (for the first time for ³He) with high precision on the MAMI-B accelerator (Mainz, Germany) with a tagged photon beam and the large acceptance detector DAPHNE. The dynamics of baryon resonances along the periodic table is analyzed, and they are compared with the sum of partial reactions on proton and deuteron. Preparation and the first stage of polarization measurements of photoabsorption cross sections on proton in the Δ resonance region are reported.     

Experiments with internal targets at the VEPP-3 electron storage ring

An overview of the recently completed, current, and planned experiments with internal targets at the VEPP-3 electron-positron storage ring in Novosibirsk is given. The results of the experiment to separately measure the deuteron form factors in elastic ed scattering in the range of momentum transfer Q ² = 8?15 fm^?2 are provided. The results of measuring the tensor analyzing power components of the tensor-polarized deuteron photodisintegration reaction in the range of γ-quantum energies E _γ = 25?600 MeV are presented. The tensor analyzing powers of the coherent photoproduction of a neutral pion on a tensor-polarized deuteron have been measured for the first time. The almost-real photon tagging system being created is discussed. The status of the experiment under way to determine the contribution of two-photon exchange to the elastic ep scattering cross section is described.     

Consistent treatment of relativistic corrections in deuteron photodisintegration in a one-pion-exchange model

Using a one-pion-exchange model for the nucleon-nucleon interaction the relativistic corrections to potential and to the electromagnetic operators are derived in a power expansion of (p/M). All corrections up to the order (p/M)³ are consistently included. Numerical results are shown for differential cross section and polarization observables for deuteron photodisintegration. A sizeable influence of relativistic effects on some observables is found even at low energies. A comparison of our operators with the expressions of other authors is given.Supported by Deutsche Forschungsgemeinschaft (SFB 201)     

P-violating effects in the polarization phenomena of the γ + D → N + P reaction near the threshold

Since at the threshold the P-odd amplitude of deuteron photodisintegration (γ + D → P + N) is determined by three independent multipole amplitudes (describing the El →¹S₀, El →³S₁, and M2 →³S₁ transitions), at least three different experiments on measuring the P-odd polarization characteristics of the γ + D → P + N process are needed (provided that P-odd threshold amplitudes are known) in order to determine the multipole amplitudes. A P-odd dependence of the threshold cross section on the polarizations of the colliding γ-quantum and deuteron is established and P-odd contributions to the polarization vector of protons formed in the γ + D → P + N process are found. The P-odd characteristics are calculated in terms of P-even and P-odd threshold amplitudes.     

Role of the D 13 and S 11 Resonances in Deuteron Photodisintegration

The influence of the N(1520) and N(1535) isobar resonances in deuteron photodisintegration is investigated. The isobar configurations are treated in impulse approximation using one-pion exchange for the transition potentials. Isobar admixtures are included in scattering waves as well as in the deuteron. Their influence on the total and differential cross section and various polarization observables, e.g., nucleon polarization and photon asymmetry is small in the Δ resonance region, but not any longer negligible at higher energies. Received July 14, 1994; accepted for publication November 28, 1994     

Investigation of the reaction D(γ, <Emphasis Type="Italic">n</Emphasis>)H near the threshold by means of powerful femtosecond laser radiation

The possibility of studying photonuclear reactions near the threshold by means of powerful femtosecond lasers is explored by considering the example of deuteron photodisintegration. The respective experiment was performed by employing the terawatt femtosecond laser facility of the International Laser Center at Moscow State University. The radiation from this facility is characterized by a pulse energy of up to 50 mJ, a duration of 50 fs, a repetition rate of 10 Hz, and a wavelength of 805 nm. This provides a power above 10¹⁸ W/cm². Intense relativistic-electron and photon beams of energy up to 10 MeV were obtained after the optimization of relevant experimental parameters, including the focus of the laser beam, its time structure, and the choice of target. The use of these beams made it possible to study neutron generation in heavy water, to measure the time of neutron moderation, and to determine the detection efficiency. The experimental data obtained in this way are in qualitative agreement with the results of simulations based on the GEANT-4 and LOENТ code packages and indicate that it is possible to create a neutron source on the basis of the aforementioned laser. The cross section measured for deuteron photodisintegration complies with theoretical estimates available in the literature.     

Preliminary results of the study of the d(d,n)3He reaction in the astrophysical energy range with the use of a Hall plasma accelerator

The possibility of using a plasma accelerator based on a pulsed Hall ion source to study the characteristics of pd, dd, d³He, ³He, and⁴He reactions in the astrophysical energy range (2–12 keV) has been considered. The preliminary experimental data on measurement of the astrophysical S factor for the dd reaction (dd → ³He + n (2.5 MeV)) at average deuteron collision energies E _col = 4.5 and 4.95 keV and the deuteron beam energy spread FWHM = 18% are reported. The found value of the S factor is in agreement with the results of the experiments carried out by us previously using linear plasma in the inverse Z-pinch configuration.     

Studies of the lightest nuclei in electromagnetic processes

Recent theoretical studies of electromagnetic processes with the ³H, ³He, and ⁴He nuclei are considered. In connection with the results obtained, the role of the NNN forces and relativistic effects, manifestations of components of nuclear states with considerable relative momenta, the degree of distinctness of the giant resonance in the ⁴He photodisintegration, and accuracy of the experimental data are discussed.     

Different formulations of <Superscript>3</Superscript>He and <Superscript>3</Superscript>H photodisintegration

Different momentum space Faddeev-like equations and their solutions for the radiative pd-capture and the three-nucleon photodisintegration of ³He are presented. Applications are based on the AV18 nucleon-nucleon and the Urbana IX three-nucleon forces. Meson exchange currents are included using the Siegert theorem. A very good agreement has been found in all cases indicating the reliability of the used numerical methods. Predictions for cross-sections and polarization observables in the pd-capture and the complete three-nucleon breakup of ³He at different incoming-deuteron/photon energies are presented.     

Relativistic corrections to electron scattering by 2H, 3He,and 4He

Relativistic corrections to the scattering of electrons by a nonrelativistic nucleus are calculated, using the method of Close and Copley, and Krajcik and Foldy. Particular attention is paid to the deuteron, ³He and ⁴He. It is found that these corrections are substantially the same as those calculated by F. Gross for the deuteron. The corrections to ³He have the effect of moving the diffraction minimum, as calculated in a nonrelativistic model, outward by as much as 0.32 fm^?2. Smaller corrections are found for ⁴He.     

Microscopic description of diffractive deuteron breakup by <Superscript>3</Superscript>He nuclei

A microscopic formalism for describing observed cross sections for deuteron breakup by threenucleon nuclei was developed on the basis of the diffraction nuclear model. A general formula that describes the amplitude for the reaction ²H(³He, ³Hep)n and which involves only one adjustable parameter was obtained by using expansions of the integrands involved in terms of a Gaussian basis. This formula was used to analyze experimental data on the exclusive cross sections for deuteron breakup by ³He nuclei at the projectile energy of 89.4MeV. The importance of employing, in calculations, a deuteron wave function that has a correct asymptotic behavior at large nucleon–nucleon distances was demonstrated.     

Studies of single-neutron holes in the transitional nuclei N = 83–89: The 142Ce(d,t)141Ce and 142Ce(3He, α)141Ce pick-up reactions

The level structure of ¹⁴¹Ce up to 3.7 MeV excitation energy has been investigated by the (d, t) and (³He, α) reactions using 17 MeV deuteron and 24 MeV ³He beams respectively. The angular distributions have been analyzed with standard DWBA calculations and spectroscopic factors are deduced. The experimental information is compared to unified model calculations involving both one-particle and two-particle one-hole configurations with quadrupole and octupole vibrations of the underlying N = 82 and N = 84 core.     

Relativistic corrections to electron scattering by the deuteron and triton

Relativistic corrections to electron-deuteron and electron-³He scattering have been calculated. the deuteron corrections agree substantially with the results of Gross and the ³He corrections are approximately equal in magnitude to those of Cocho and Flores.     

Target asymmetry measurement of deuteron photodisintegration at a photon energy of 550 MeV

The target asymmetry of the deuteron photodisintegration was measured at a photon energy of 550±50 MeV and at proton center-off-mass angles between 25 and 155 degrees.D-butanol andND ₃ were used as target material yielding a maximum deuteron polarization of 41%. Proton and neutron were detected in coincidence. The data show a structure which cannot be described by the existing analyses.