Study of the reaction 12C(γ, n 3He)2α

The possibility of separating, with the aid of photoemulsion, channels of the reaction ¹²C(γ, n ³He)2α that involve the formation of ⁷Be and ⁸Be intermediate nuclei in excited states is studied. The experimental energy distributions of these nuclei are obtained. The relative yields from these reaction channels are estimated.     

Measurement of the2H(d, γ)4He reaction at intermediate excitation energies

The²H(d, )⁴He differential cross section was measured at deuteron laboratory energies of 20, 24, and 28 MeV between _cm=45° and _cm=135°. AtE _d =28 MeV a complete angular distribution was determined and fitted with Legendre polynomials. The ratioR=d/d (_cm=90°)/d/d (_cm=135°) was measured for each deuteron energy.     

Theoretical Study of the 4He(γ, p)3H and 4He(γ, n)3He Reactions

Ab initio calculation of the total cross section for the reactions ⁴He(γ, p)³H and ⁴He(γ, n)³He is presented, using state-of-the-art nuclear forces. The Lorentz integral transform (LIT) method is applied, which allows exact treatment of the final state interaction (FSI). The dynamic equations are solved using the effective interaction hyperspherical harmonics method. In this calculation of the cross sections the three-nucleon force is fully taken into account, except in the source term of the LIT equation for the FSI transition matrix element.     

Investigation of excited states in56Co with the54Fe(3He,pγ)56Co reaction

The two-particle stripping reaction⁵⁴Fe(³He,p γ)⁵⁶Co at \(E_{3_{He} } \) =15.15 MeV was used to investigate theγ-ray transitions and to determine branching ratios, possible spin assignments and mean lifetimes of levels in⁵⁶Co up to 5.5 MeV excitation energy. Gamma-rays for both angular correlations and lifetime measurements were observed with a 43 cm³ Ge(Li) detector in coincidence with proton-groups detected at 0°. The level scheme and lifetime values are compared with the predictions of various shell model calculations.     

Study of the187W states excited in the (n, γ) reaction

A singles-ray spectrum and a spectrum of summed amplitudes of coinciding pulses (SACP) were measured in the¹⁸⁶W(n, )¹⁸⁷W reaction experiment on the thermal neutron beam. It was for the first time that the data on¹⁸⁷W-transitions were obtained in the excitation energy region from 1500–2500 keV. The neutron binding energy was determined to beB _n=5467.25 (4) keV (statistical error only). In result the level scheme of¹⁸⁷W was developed in the excitation energy interval 1E _f < 3.4=" mev,=" which=" contained=" 105=" levels=" with=" about=" 70=" of=" them=" being=" identified=" for=" the=" first=" time.=" the=" experimental=" values=" for=" summed=" intensities=" of=" two-step=" cascades=" were=" established=" to=" exceed=" those=" predicted=" by=" the=" modern=" statistical=" theory=" (by=" 36±6%).=" this=" is=" explained=" by=" a=" considerable=" contribution=" of=" few-quasiparticle=" components=" to=" wave=" functions=" of=" compound=" and=" intermediate=">     

Discovery of deeply bound π− states in the208Pb(d,3He) reaction

Narrow lines were observed around 133 MeV excitation energy in the²⁰⁸Pb(d,³He) reaction atT _d=300 MeV/u using the Fragment Separator System at GSI. They are assigned to the deeply boundπ ^??²⁰⁷Pb states with configurations of $\left( {2p} \right)_{\pi ^ - } $ (3p_1/2, 3p_3/2) _n ^?1 .     

Study of the 3He(4He,γ)7Be and 3H(4He,γ)7Li Reactions in an Extended Two-Cluster Model

 The ³He(⁴He, γ)⁷Be and ³H(⁴He, γ)⁷Li reactions are studied in an extended two-cluster model which contains α + h/t and ⁶Li + p/n clusterizations. We show that the inclusion of the ⁶Li + p/n channels can significantly change the zero-energy reaction cross sections, S(0), and other properties of the ⁷Be and ⁷Li nuclei, like the quadrupole moments Q. However, the results agree with the known correlation trend between S(0) and Q. Moreover, we demonstrate that the value of the zero-energy derivatives of the astrophysical S-factors are more uncertain than currently believed. Received June 17, 1999; revised February 22, 2000; accepted for publication April 17, 2000     

Inelastic production of neutral pions in the4He(γ, πℴp)3H reaction

The yield of the⁴He(, p)³H reaction has been studied in a bremsstrahlung beam of photons with a maximum energy of 450 MeV. The measurements were made on an experimental setup consisting of a total absorption Cerenkov gamma spectrometer and a helium streamer chamber. A kinematic analysis is made of the angular distributions of the disintegration products of the⁴He nucleus to study the mechanism of inelastic photoproduction of neutral pions. The relatively high event density in the region of small proton-triton separation angles is attributable to the quasielastic mechanism of the reaction in which pion photoproduction is accompanied by excitation of the⁴He nucleus.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 51–56, September, 1989.     

Pion scattering on 3H and 3He nuclei in the Δ33(1232) region

Elastic scattering of π ^± mesons on ³H and ³He nuclei at energies around the Δ₃₃(1232) resonance is considered. The amplitudes for single and double scattering are calculated on the basis of the nonrelativistic diagram technique. The spin and isospin structure of pion-nucleon amplitudes is fully taken into account. The resulting theoretical predictions for the differential cross sections are compared with available experimental data.     

Distributions of products of the quasifree knocking-out reaction (p,p′n) on halo nuclei in the intermediate-energy region

Expressions for the distribution functions of products of the reaction (p, p′n) of valence neutron knocking-out from halo nuclei were derived using space-time correlation functions. The possibility of using this reaction to study the neutron halo structure was analyzed.     

Study of the reaction130Te(n, γ)131Te

Energies and intensities of the gamma-ray transitions following the thermal neutron capture in¹³⁰Te are determined. The neutron separation energy for¹³¹Te is evaluated to be 5929.4 ±±0.3 keV. A statistically significant correlation between the reduced transition intensities and the spectroscopic factors from the (d, p) reactions is found. Evidence for the presence of potential capture mechanism is given.On leave fromAl-Faateh University, Physics Department, P.O. Box 13371, Tripoli, Libya.     

New experimental data on the 10B(n, αt)4He reaction

A new technique is described that makes it possible to detect reaction products with the escape of charged particles occurring on components of working gas under the action of fast neutrons. This technique is unique since it offers the possibility of studying reactions for which more than two charged particles are generated in an output channel. This work studies interactions between neutrons and ¹⁰B nuclei, where two α-particles and tritium nucleus are produced as reaction products.     

Experimental observation of electron screening for the D(p, γ)3He nuclear reaction in titanium Deuteride TiD

Characteristics of the pd reaction (p + d → ³He + γ(5.5 MeV)) in titanium deuteride at astrophysical proton-deuteron collision energies ranging from 5.3 to 10.5 keV are investigated. Experiments are conducted on the pulsed plasma Hall accelerator at Tomsk Polytechnic University (Tomsk, Russia). The number of accelerated protons in a pulse 10 μs long is 5 × 10¹⁴ at a repetition rate of 7 × 10^?2 Hz. Gamma rays with an energy of 5.5 MeV are recorded by eight detectors based on NaI(Tl) crystals (100 × 100 × 400 mm) arranged around the TiD target. The dependence of the astrophysical S factor for the pd reaction on the proton-deuteron collision energy and the electron screening potential of protons interacting with deuterons in titanium deuteride are measured for the first time.     

Systematical law of (n, γ) reaction cross sections of even-even nuclei

We have derived a formula for the neutron radiative capture cross section in the framework of a statistical model approach to nuclear reactions. Based on this formula, new systematics are established between the (n, γ) reaction cross section and the energy level density of a compound nucleus or a relative neutron excess of an even-even target nucleus for neutron incident energy above the resonance region to MeV. Good agreement with experimental data suggests that this new systematical law is helpful to analyze the experimental data.     

Quasi-free processes in 6Li(3He,pα)4He reaction at low energies

The ⁶Li(³He, pα)⁴He reaction was studied experimentally at 3.5, 4.4 and 5.5 MeV in the quasi-free reaction kinematical region. The effects of a resonance in the virtual ²H(³He, p)⁴He reaction on the three-body reaction cross section were investigated.     

Pion electroproduction in the 3He(e,é π+)3H reaction at intermediate energies

The differential coincident pion electroproduction cross section in the ³He(e,é π⁺)³H reaction has been measured with high resolution with the three-spectrometer set-up at the Mainz Microtron (MAMI) electron accelerator. Measurements were performed at the four incident energies E₀ = 855, 675, 600, and 555 MeV at fixed four-momentum transfer Q² = 0.045 GeV², with the pions detected in parallel kinematics. This enables a separation of the measured cross section into the transverse and longitudinal structure functions by means of the Rosenbluth method. The experimental data are compared to model calculations, in which the elementary pion production amplitude includes the standard Born-amplitudes and also delta and higher resonance terms. Three-body Fadeev wave functions are used and the final state interaction of the outgoing pion is taken into account. The calculation describes the data only after medium modifications of the delta and of the pion are included.     

Study of the 4He(e,e′d)pn Reaction

 The cross section for the ⁴He(e,e′d)pn reaction has been measured in parallel and in (q, ω)-constant kinematics for values of the three-momentum transfer of 406, 495 and 595 MeV/c, and for a range in missing momentum. Just above threshold this reaction can be characterized as a spin/isospin flip transition of the involved pn pair. By using two electron energies (576 and 370 MeV) the longitudinal and transverse structure functions could be separated. The cross sections turn out to be purely transverse, as expected for a spin/isospin flip transition. The data are well described by new covariant and current-conserving calculations that include the major final-state interaction effects. Received August 20, 1998; modified October 12, 1998; accepted for publication January 30, 1999