Deuteron Angular Distributions Research Articles

Proton Spectroscopic Factors Deduced from Helium-3 Global Phenomenological and Microscopic Optical Model Potentials

Global phenomenological GDP08 and microscopic helium-3 optical model potentials have been recently derived. We evaluate these two potential sets by comparing the elastic scattering data of 25 MeV 3He on 16O, 18O, 19F, 23Na, 24Mg, 25Mg, 26Mg, 27Al, 28Si, 30Si, 31P, 32S, 34S, 35Cl, 37Cl, and 39K isotopes. Using the deuteron angular distributions calculated with the distorted wave Born approximation model, we extract the ground-state proton spectroscopic factors from (3He, d) reactions on the same set of nuclei. The extracted proton spectroscopic factors are compared with the large-basis shell-model calculations.

Observation of a breakup-inducedα-transfer process for some bound states ofO16populated by theC12(Li6,d)O16*reaction

Background: The ${}^{12}\mathrm{C}{(}^{6}\mathrm{Li},d)$ reaction has been used as an indirect method to calculate the astrophysical $S$ factor for the $^{12}\mathrm{C}$($\ensuremath{\alpha},\ensuremath{\gamma})$ reaction at Gamow energy (300 keV).Purpose: The ${}^{12}\mathrm{C}{(}^{6}\mathrm{Li},d)$ reaction is usually interpreted in terms of direct transfer. In this work we investigate the reaction mechanism and determine the effects of breakup on transfer and therefore on the extracted spectroscopic amplitudes.Method: The deuteron angular distributions for the ${}^{12}\mathrm{C}{{(}^{6}\mathrm{Li},d)}^{16}{\mathrm{O}}^{*}$has been measured at 20 MeV, populating discrete states of $^{16}\mathrm{O}$. continuum discretized coupled channel-coupled reaction channel (CDCC-CRC) calculations have been used to analyze the data.Results: Results show a new reaction mechanism, where transfer occurs after the breakup of the loosely bound $^{6}\mathrm{Li}$ in the population of some bound states of $^{16}\mathrm{O}$. A comparison of the CDCC-CRC calculations with respect to the measured data were used to determine the $\ensuremath{\alpha}$ spectroscopic amplitudes and factors for the different states of $^{16}\mathrm{O}$. Using the spectroscopic amplitudes obtained in this work, the $E2$ $S$ factor for the $^{12}\mathrm{C}$($\ensuremath{\alpha}$,$\ensuremath{\gamma}$) reaction has been calculated in the framework of a two-body potential model and compared to measurements.Conclusions: The present study very clearly shows that the breakup and transfer coupling effects are strong in the ${}^{12}\mathrm{C}{(}^{6}\mathrm{Li},d)$ reaction. The present work extracts, in the framework of a coupled reaction channel theory, the spectroscopic amplitudes of the bound and unbound states of $^{16}\mathrm{O}$. All previous analysis and new measurements should therefore be reexamined from this viewpoint to extract the astrophysical observables correctly.

Influence of prepulse plasma formation on neutron production from the laser–target interaction

The interaction of an intense ultrashort pulse laser with a planar uniform target was studied with a two-dimensional relativistic electromagnetic particle-in-cell method to determine the acceleration of deuterons and production of neutrons. A Au-CD2 double-layer planar target with thickness of ∼1μm and a preplasma of variable length was used to generate high-energy deuterons as a precursor for neutron production. The deuteron energy and angular distributions and the neutron production from D(d,n)–He3 nuclear fusion reactions were studied as a function of the preplasma scale length and target thickness. For very thin (submicron) targets the preplasma increases the neutron yield only marginally, but for realistic targets with thickness of a few microns the preplasma enhances the neutron yield by two orders of magnitude. Both the average deuteron energy and neutron yield peak at an optimum preplasma scale length Lpopt≈1∕k0 (k0 laser wave vector), which is of the order of one inverse laser wave vector.

New stellar reaction rates for 25Mg(p, gamma )26Al and 25Al(p, gamma )26Si.

Existing experimental proton stripping reaction data on {sup 25}Mg leading to threshold states in {sup 26}Al are reinvestigated and reanalyzed in a consistent and improved manner. We use unbound state form factors in the DWBA analysis of the measured deuteron angular distributions to deduce absolute rather than relative proton partial widths. For higher-lying resonances these values are compared to widths obtained from ({ital p},{gamma}) work. It is also shown that several of the unique {ital J}{sup {pi}} values assigned previously to {sup 26}Al states are erroneous. This paper reports on a reanalysis of spins, parities, and isospins for {sup 26}Al states located at {ital E}{sub {ital x}}{lt}8.00 MeV. We deduce new stellar rates for the reaction {sup 25}Mg({ital p},{gamma}){sup 26}Al and compare our results with previous values. Furthermore, shell-model calculations for the mass {ital A}=26 system are performed. Theoretical excitation energies, {ital J}{sup {pi}} values, {gamma}-ray transition strengths, spectroscopic factors, and proton partial widths are compared to experimental data and new shell-model assignments of experimental states in {sup 26}Al are derived. We estimate Coulomb displacement energies of excited {sup 26}Mg and {sup 26}Si mirror states and present new analog assignments for {ital T}=1 triplet states in {ital A}=26 nuclei. Basedmore » on shell-model results and analog state information we present updated stellar rates for the {sup 25}Al({ital p},{gamma}){sup 26}Si reaction. {copyright} {ital 1996 The American Physical Society.}« less

Observation of 12C cluster transfer by angular correlation measurements.

Angular correlations between deuterons and alphas in the reaction $^{12}\mathrm{C}$${(}^{14}$N,d${)}^{24}$${\mathrm{MG}}^{\mathrm{*}}$(\ensuremath{\alpha}${)}^{20}$Ne(g.s.) at beam energies of 30, 33, 36, and 42 MeV have been used to investigate the reaction mechanism. Evidence for possible $^{12}\mathrm{C}$ cluster transfer to the 13.45 MeV ${6}^{+}$ state in $^{24}\mathrm{Mg}$ is presented. The transfer of $^{12}\mathrm{C}$(${2}^{+}$) clusters seems to be the dominant process. In addition to the correlation measurements, deuteron angular distributions were measured at 33 and 42 MeV and an excitation function at a lab angle of 8\ifmmode^\circ\else\textdegree\fi{} was obtained between 30 MeV and 45 MeV in 3 MeV steps. The angular correlations, deuteron angular distributions, and the excitation function were fitted using the finite range distorted wave Born approximation (FRDWBA) and the Hauser-Feshbach formalism of compound nucleus formation.

Explosive hydrogen burning of 35Cl

Proton threshold states in 36Ar have been studied via the reactions 35Cl( 3He, d) 36Ar, 32S( 6Li, d) 36Ar, 32S(α, γ) 36Ar, 35Cl(p, γ) 36Ar and 35Cl(p, α) 32S to investigate their influence on a possible SC1 reaction cycle in explosive hydrogen burning. Three new states in 36Ar have been observed in the ( 3He, d) reaction at E x = 8806, 8887 and 8923 keV. Deuteron angular distributions were measured for 14 states near the 35Cl+p threshold and were analyzed with DWBA calculations. Values of transferred orbital angular momenta, spectroscopic factors and proton partial widths were determined. Gamma-ray spectra have been measured at ten (p, γ) resonances. Three new resonances were observed at E R = 311, 416 and 627 keV, corresponding to 36Ar states at E x = 8806, 8909 and 9117 keV, respectively. Excitation and resonance energies, γ-ray branching ratios and resonance strengths are presented. The astrophysical implications of our results for explosive hydrogen burning of 35Cl are discussed.

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.

Alpha-transfer study of 23Na

Abstract The reaction 19 F( 6 Li, d) 23 Na has been studied at a beam energy of 34 MeV using a high resolution magnetic spectrometer. A total of 36 states in 23 Na have been observed in the range E x = 4–13MeV and deuteron angular distributions obtained for 26 states. Compound processes accounted for less than 10% of the forward angle cross section in most instances. Finite-range distorted-wave Born approximation calculations have been performed and compared with the data. The calculations reproduced the observed angular distributions well, allowing relative α-particle spectroscopic factors to be extracted and several new or improved spin assignments to be made. The 6 Li- 19 F optical potential was derived from elastic scattering data obtained in the present work. The results are discussed with reference to the rotational structure of 23 Na.

Multistep processes in the 26Mg(p, d) 25Mg reaction at 24.0 MeV

Deuteron angular distributions from the 26Mg(p, d) 25Mg reaction at E p = 23.95 MeV and the 25Mg(d, d') 25Mg reaction at E d = 14.96 MeV have been measured with a split-pole magnetic spectrograph. Coupled-channels calculations have been performed to calculate the angular distributions from the inelastic excitation of the 7 2 + and 9 2 + members of the ground-state band (GSB) in 25Mg. The pick-up data have been analyzed with DWBA and CCBA. Two types of deuteron potentials were used in the calculations: an optical-model potential and an adiabatic potential. Only the adiabatic potential yields satisfactory results. The DWBA description of the (p, d) data is not satisfactory — even for the single-particle transitions. Much better results are obtained with CCBA, especially for the ground state and for the heads of both low-lying K π = 1 2 + bands. Reorientation effects appear to be very important both for the shape and the height of the calculated angular distributions. Spectroscopic amplitudes calculated from the Nilsson model do not lead to good descriptions for the states of both low-lying K π = 1 2 + bands — even when band mixing is taken into account. The (p, d; d, d') paths seem to be overestimated in the present calculations for the GSB.

A study of42Sc using the40Ca( α,d)42Sc reaction

States of T=0 in 42Sc were populated via the 40Ca( alpha ,d)42Sc reaction at a bombarding energy of 25.5 MeV. Deuteron angular distributions were measured to the states at 0.61 MeV (1++7+), 1.491 MeV (3+) and 1.511 MeV (5+). The relative strengths of states up to an excitation of 3.03 MeV were measured and compared with the predictions of a model which considered excitation of the 40Ca core. Reasonable agreement is found for states up to 2.27 MeV. The results are consistent with the 1.846 MeV level being the Jpi =3+ head of a deformed band but not with the level at 2.391 MeV being the 4+ member of this band.

Neutron hole states in 91Mo and 93Mo studied by the (p, d) reaction

The level structure of 91Mo and 93Mo has been investigated with the 92, 94Mo(p, d) 91, 93Mo reactions at E p = 40 MeV. Deuteron angular distributions were measured for 26 groups in 91Mo up to 9 MeV excitation (including five analog states), and 24 groups in 93Mo up to 13 MeV excitation (including five analog states). The l n values and transition strengths were determined from a DWBA analysis. Several new spin and parity assignments were made. The results are compared to the 92, 94Mo(d, t), 90, 92Zr(p, d), 88Sr(d, t) and 92, 94Mo(d, 3He) reactions. All results are compared to simple sum-rule predictions. The summed transition strengths in 91, 93Mo agree reasonably well with sum-rule predictions except for the 1f 5 2 transitions. The 1f 5 2 strength, and to a lesser degree the 1g 9 2 and 2p strengths, are severely fragmented in 93Mo in contrast to 87Sr, 89Zr and 91Mo. We show that the N = 50 core in the 92Mo ground state is very well closed. In the 94Mo ground state, the neutrons beyond the N = 50 core occupy only about 65% of the 2d 5 2 orbit. For the analog states in 91,93Mo, neither the effective binding nor the separation energy form factor gives consistently better results as regards both the C 2 S values and the quality of the DWBA fits. The Q-value of the 92Mo(p, d) 91Mo reaction was found to be Q = −10.432 ± 0.025 MeV.

Neutron-Gamma Competition Following (d,d′) Reactions

The ($d,{d}^{\ensuremath{'}}n$) reaction has been studied in $^{61}\mathrm{Ni}$ and other targets, using 19-MeV deuterons. Deuteron angular distributions and yields indicate that the ($d,{d}^{\ensuremath{'}}$) reaction is predominantly direct at forward angles, but probably has a large compound-nuclear component at backward angles, and observed angular correlations for ${d}^{\ensuremath{'}}\ensuremath{-}n$ coincidences indicate that the neutrons are mainly products of evaporation from a $^{61}\mathrm{Ni}$ compound nucleus. The fractional yield, ${F}_{n}=\frac{{\ensuremath{\Gamma}}_{n}}{\ensuremath{\Gamma}}$, for neutron emission is found to be substantially below unity for $^{61}\mathrm{Ni}$ excitation energies ${E}_{i}$ extending to several MeV above the neutron binding energy ${B}_{n}$ (e.g., ${F}_{n}\ensuremath{\simeq}0.75$ at ${E}_{i}\ensuremath{-}{B}_{n}=2$ MeV), indicating the importance of competition from $\ensuremath{\gamma}$-ray emission. For ${E}_{i}\ensuremath{-}{B}_{n}<3$ MeV, ${F}_{n}$ is independent of deuteron angle and its magnitude can be accounted for in terms of the statistical model. Because the relative neutron and $\ensuremath{\gamma}$-ray emission widths are strongly dependent on the $^{61}\mathrm{Ni}$ spin population, this lack of dependence of ${F}_{n}$ on deuteron detection angle suggests that the $^{61}\mathrm{Ni}$ spin population is similar for direct and compound-nuclear ($d,{d}^{\ensuremath{'}}$) reactions. For ${E}_{i}\ensuremath{-}{B}_{n}>3$ MeV, the value of ${F}_{n}$ at forward deuteron angles is anomalously low. Results are also presented for the ($d,{d}^{\ensuremath{'}}n$) reaction in $^{25}\mathrm{Mg}$, $^{57}\mathrm{Fe}$, $^{91}\mathrm{Zr}$, and $^{119}\mathrm{Sn}$.

Study of the level scheme of 117In via proton transfer reactions

The ( 3He, d) and (α, t) reactions on 116Cd have been used to study levels in 117In up to 2.8 MeV excitation. The measurements were performed at the 3He and α-particle bombarding energies of 27 and 25.5 MeV, respectively, using a magnetic spectrograph. Deuteron angular distributions were compared with the distorted-wave Born approximation predictions to obtain angular momentum transfer and spectroscopic factors. Tritons were recorded at only three angles. Present results show significant configuration mixing of the proton wave function in the 116Cd ground state. The low-lying positive-parity levels of 117In are discussed in the framework of the particle core coupling model and the rotational model.

Level Structure ofV50

The reaction $^{49}\mathrm{Ti}(^{3}\mathrm{He},d)^{50}\mathrm{V}$ has been studied at 15-MeV incident energy with an over-all energy resolution better than 20 keV full width at half maximum. 54 states were observed in $^{50}\mathrm{V}$ up to 6-MeV excitation, and corresponding deuteron angular distributions were measured in the angular interval 7 to 50\ifmmode^\circ\else\textdegree\fi{}. Spectroscopic information has been extracted for 30 of the stronger or well-isolated transitions by means of a distorted-wave analysis of the differential cross sections. The results are compared with nuclear-model predictions.

The structure of 36Ar and 38Ar via the ( 3He, d) reaction on 35Cl and 37Cl

The level structures of 36Ar and 38Ar have been investigated with the 35,37Cl( 3He, d) 36,38Ar reactions at a bombarding energy of 12 MeV. Deuteron angular distributions were measured for 31 levels in 36Ar up to 8.5 MeV excitation and 29 levels in 38Ar up to 6.9 MeV excitation. The l p values and transition strengths were determined from a distorted wave Born analysis of the angular distributions. The results for the positive parity states of 36Ar and 38Ar are in reasonable agreement with a shell-model calculation which considers only Id 3 2 and 2 s 1 2 nucleons outside a closed 28Si core. The major components of the ( f 7 2 d 3 2 5) T = 1 configuration in 38Ar for J π = (3, 4, 5) − and of the ( f 7 2 d 3 2 3) T = 0 configuration in 36Ar for J π = (3, 5) − were identified. For the f 7 2 transitions in 38Ar, and to a lesser extent in 36Ar, the observed severe fragmentation of strength shows that a model involving core polarization rather than a simple weak coupling model is applicable in describing the structure of these nuclei. All the p 3 2 . transition strength to T < states was accounted for in 36Ar but only 12 % in 38Ar. It appears that the P 3 2 −f 7 2 single-particle energy splitting is significantly smaller in 36Ar than in 38Ar. The angular distributions of all known 3 − states are consistent with mixed l = 1+3 transitions, showing that configuration admixtures between the ( p 3 2 d n 3 2 ) and ( f 7 2 d n 3 2 ) configurations are important.

A study of the 35Cl levels by means of the 34S(3He, d)35Cl reaction

Abstract The 34S(34He, d)35Cl reaction has been studied with high resolution at 11 MeV bombarding energy. A detailed level scheme for 35Cl has been determined up to an excitation energy of 5.8 MeV revealing several previously unobserved states. The lp values and absolute spectroscopic factors extracted from a DWBA analysis of the experimental deuteron angular distributions have provided information on the single proton character of the wave functions for the T = 1 2 states as well as for the lowest T = 3 3 isobaric analogue of the 35S ground state. A comparison between the present data and those of previous experiments is made and the results are discussed in terms of the existing shell-model and unified model calculations of this nucleus. Information on Coulomb displacement and symmetry energies is also extracted.

Proton Excitation inV51

The ${\mathrm{Ti}}^{50}({\mathrm{He}}^{3},d){\mathrm{V}}^{51}$ reaction has been studied at 16.4-MeV incident energy with an over-all energy resolution of 20 keV full width at half maximum (fwhm). 57 levels in ${\mathrm{V}}^{51}$ were identified up to 9.5-MeV excitation, and corresponding deuteron angular distributions were recorded in the angular interval 7\ifmmode^\circ\else\textdegree\fi{} to 50\ifmmode^\circ\else\textdegree\fi{}. Spectroscopic information has been extracted for 27 of the strongest or most well-isolated transitions by means of a distorted-wave analysis of the differential cross sections. The results are compared with nuclear-structure model predictions.

The 54Cr( 3He, d) 55Mn reaction

The proton states in 55Mn have been studied by means of the 54Cr( 3He, d) reaction with 10.0 MeV 3He ions. Deuteron angular distributions for stripping transitions to states below 5.5 MeV excitation were measured using the MIT multiple-angle spectrograph. A DWBA analysis was carried out to determine l p values and transition strengths. The observed level structure of 55Mn is compared with those from ( 3He, d) reactions leading to 53Mn and 51Mn.

A study of the 32S levels and the analogue levels of 32P by the 31P( 3He, d) 32S reaction

The 31P( 3He, d) 32S reaction has been studied with high resolution at 12 MeV bombarding energy. A detailed level scheme for 32S has been determined up to an excitation energy of 9.5 MeV revealing several previously unobserved states. The l p values and absolute spectroscopic factors extracted from a DWBA analysis of the experimental deuteron angular distributions have provided information on the wave functions for the T = 0 states as well as for the T = 1 isobaric analogue states of 32P. A comparison between the present data and those of previous experiments is made, and the results are discussed in terms of existing theoretical work in this mass region. Information on Coulomb displacement and symmetry energies is also extracted.

( 3He, d) reactions on the even tin isotopes

Deuteron angular distributions from the ( 3He, d) reaction on the even Sn isotopes leading to states of the corresponding odd Sb isotopes ( A = 113 to 125) have been studied at an incident 3He energy of 18 MeV. DWBA calculations using the JULIE code have been performed to assign l p values and extract spectroscopic factors. On the basis of this analysis, levels were found carrying large fractions of the 1 g 7 2 , 2 d 5 2 and 1 h 11 2 proton single-particle strength. The splitting of the 2 d 3 2 and 3 s 1 2 strength in many levels is more pronounced. Spacings and spectroscopic factors for the low-lying states are in fair agreement with calculations of Kisslinger and Sorensen.