Proton Pickup Research Articles

Proton pick-up from nuclei in the middle of the 1p shell

The (d,3He) reaction has been used to excite proton hole states in8Li,9Be and10Be. Angular distributions have been measured and have been analyzed in terms of the DWBA to get spectroscopic factors for the considered transitions. Excitation energies and transition strengths are compared with the results of Cohen and Kurath's intermediate coupling shell model calculations, where the two models of the effective interaction produce different results especially for transitions to final states in mass 8 and 10 nuclei. The experimental results are clearly in favour of the (6–16) 2 BME interaction. A positive parity state in10Be predicted by the calculations has been looked for and found at 9.60 MeV.

Proton hole states excited by monoenergetic gamma quanta

Earlier work has shown how information about the giant dipole resonance and proton hole states can be inferred from high resolution photoproton spectra obtained in irradiation with the 17.62 MeV gamma quanta produced by the7Li(p, γ)8Be-reaction. To exploit this method the high energy photoproton spectra from45Sc,51V,59Co,58Ni,63Cu and natural nickel have been measured with 60–120 keV resolution. The absolute cross sections for transitions to levels in the daughter nucleus have been determined. The results are compared with a simple model assuming a semidirect reaction proceeding via a dipole doorway state. Good correlation is found between the cross sections and the spectroscopic factors measured in proton pick-up reactions. Comparison with the total photoproton cross section for58Ni indicates, however, that the majority of protons are emitted at lower energies from more complicated states.

The reaction 11B(γ, p) 10Be ∗ at intermediate energies

The yield of the reaction 11B(γ, p) 10Be ∗ has been measured for bremsstrahlung end-point energies between 100 and 800 MeV by observing de-excitation γ-rays from the first excited state. The number of nucleons available for the reaction is determined and compared to theoretical predictions for proton pick-up on 11B.

Proton occupation numbers for 44Ca

The (d, 3He) proton pickup reaction on 44Ca has been studied at a deuteron energy of Ed = 19.0 MeV using the Minnesota MP Tandem Van de Graaff. Differential cross sections were measured at forward angles and spectroscopic factors were extracted in the usual fashion for the transitions to five states of 43K. The results are compared with previous proton pickup and stripping reactions on the even Ca isotopes. Only about half of the sd hole state excitation strength observed in the stripping reactions could be found in the pickup from the fp orbitals if the data are analyzed by standard distorted wave calculations. This discrepancy can be removed by using bound state potential radii which are slightly larger for sd orbitals than for fp orbitals.

(p,α) reaction onNb93andY89

The ($p,\ensuremath{\alpha}$) reaction has been studied at 15.2 MeV on $^{93}\mathrm{Nb}$ and $^{89}\mathrm{Y}$ and analyzed using distorted-wave Born-approximation and cluster form factors. The reaction is a direct triton pickup and compound nucleus effects are negligible. In the first case the transferred neutrons are the two extra core neutrons and the reaction behaves like a proton pickup. Positive parity states of $^{90}\mathrm{Zr}$ are populated by the transfer of ${g}_{\frac{9}{2}}$ protons with strengths in good agreement with a simple model; new levels are excited corresponding to ${p}_{\frac{3}{2}}$ and ${f}_{\frac{5}{2}}$ proton holes. In the second case the neutrons are removed from the filled $N=50$ shell; states corresponding to proton and neutron configurations in $^{86}\mathrm{Sr}$ are excited with comparable strengths and it is difficult to get unambiguous spectroscopic information.NUCLEAR REACTIONS $^{93}\mathrm{Nb}(p,\ensuremath{\alpha})$, $^{89}\mathrm{Y}(p,\ensuremath{\alpha})$, ${E}_{p}=15.2$ MeV; measured $\ensuremath{\sigma}({E}_{\ensuremath{\alpha}},\ensuremath{\theta})$, $\ensuremath{\theta}=10\ensuremath{-}160\ifmmode^\circ\else\textdegree\fi{}$, $^{90}\mathrm{Zr}$ levels up to 5.1 MeV, $^{86}\mathrm{Sr}$ levels up to 3 MeV. Reaction mechanism. DWBA analysis.

Comparative spectroscopy with the (d, τ) reaction on even Ar isotopes

The (d, τ) proton pick-up reactions on 36Ar and 38Ar have been studied at an incident energy of 52 MeV. Differential cross sections were measured and spectroscopic factors were extracted for transitions to 14 states of 35Cl and 13 states of 37Cl, respectively. Many new 5 2 + states and nearly the complete 1 d 5 2 strength have been observed in both nuclei. The width of the 1 d 5 2 spectral distribution is appreciably smaller for the semi-closed shell nucleus 38Ar than for 36Ar and 40Ar. The results are compared with those from the 40Ar(d, τ) reaction and proton stripping reactions on each of the three argon isotopes. Recent shell model calculations proved to be well suited to describe excitation energies as well as spectroscopic factors for the low-lying positiveparity states. Mirror relations were established for the nuclei 35Ar and 35Cl. In 37Cl we succeeded in observing a weak component of a 1p proton hole state at a separation energy of only 18 MeV.

Quadrupole moments of35,37Cl in the overlap representation

For 37Cl there is close agreement between the quadrupole moment measured by atomic methods and that deduced from proton pick-up spectroscopic factors, but there is probably some discrepancy in the case of 35Cl where the pick-up data are more ambiguous. The agreement casts doubt on the use of 'effective charges' for these nuclei.

Theory of overlap functions: (II). The overlap representation

Nuclear densities and the expectation values of electromagnetic operators are expressed explicitly in terms of the single particle overlap functions defined in the first paper I of this series. Using the sum rules of I some of the properties of this representation are discussed. In some cases values of nuclear electrical moments can be obtained directly from experimental data on proton pick-up and stripping reactions. As an illustration the quadrupole and hexadecapole moments of 51V are obtained with a discussion of the errors and uncertainties of the method. We find Q = −0.033 ± 0.01 b, a possibly more accurate value than that found by other methods.

The reaction 26Mg(d, τ) 25Na and the structure of 25Na

The nuclear structure of the nucleus 25Na has been studied with the (d, τ) proton pick-up reaction on 26Mg at a bombarding energy of 29 MeV with an energy resolution of 25 to 30 keV FWHM. Excited states in 25Na have been measured up to excitation energies of 8 MeV. The experimental angular distributions show good agreement with the predictions from the standard distorted-wave Born-approximation theory (code DWUCK; non-local and finite range). However, the agreement is improved considerably if the procedure of Kunz, Rost and Johnson is applied which accounts approximately for strong couplings to inelastic channels in the initial and final (strongly deformed) nuclei. The influence of this treatment on the evaluation of spectroscopic factors has been investigated and was found to be particularly pronounced for l = 0 transitions. The measured spectroscopic factors are compared to those from other experimental work and from shell-model and Nilsson-model calculations.

Proton pick-up from 92Mo

The reaction 92Mo(t, α) 91Nb has been carried out at a triton bombarding energy of 12 MeV. Angular distributions of the emitted α-particles were obtained and compared with DWBA predictions. Relative spectroscopic factors were obtained for six low-lying states and are discussed with reference to shell-model calculations.

The excitation of 64Ni by the 65Cu(t, α) reaction

Angular distributions of α-particles from the (t, α) reaction on 65Cu have been measured for 12 MeV incident tritons. Levels up to an excitation energy of 7 MeV in 64Ni were studied with a resolution (FWHM) of 10 keV. Distorted-wave Born-approximation calculations were carried out and used to assign values to the angular momentum of the transferred protons as well as to determine relative spectroscopic factors for the outer shell-model orbits. A possible connection between collective states of the 64Ni core and the proton in the 2p 3 2 orbit was investigated by comparison between these data, other proton pick-up reactions on 65Cu and the inelastic scattering of 3He and α particles from 64Ni. Evidence is found for a two-step process in the proton pick-up reaction leading to known collective states of the core.

States of 87Sr populated by deuteron pick-up from 89Y

The reaction 89Y(d, α) 87Sr has been observed at a bombarding energy of 12 MeV. Angular distributions of the emitted α-groups were recorded over the angular range 10° to 160° lab and compared with a DWBA analysis. Many levels in 87Sr appear to be populated by proton pickup from the 2 p 3 2 orbit. The levels of 87Sr populated in this reaction correspond to those observed in the 87Rb(p, n) 87Sr reaction but differ to a large extent from those seen in neutron stripping and pick-up reactions.

O18-Induced Transfer Reactions

$^{18}\mathrm{O}$-induced reactions on $^{40}\mathrm{Ca}$ and $^{54}\mathrm{Fe}$ have been studied at 48 MeV. The one- and two- proton pickup reactions were observed with large cross sections. Systematic and unexpected differences are found in the angular distributions to different final states. The reaction $^{40}\mathrm{Ca}$($^{18}\mathrm{O}$, $^{14}\mathrm{C}$) $^{44}\mathrm{Ti}$ yields spectra remarkably similar to those found in the ($^{16}\mathrm{O}$, $^{12}\mathrm{C}$) and ($^{20}\mathrm{Ne}$, $^{16}\mathrm{O}$) reactions.

Predominance of Proton Stripping Over Proton Pickup in Heavy-Ion Reactions

The statistical theory of nuclear reactions is applied to explain the strong tendency for protons to be transferred out of the projectile when heavy targets are bombarded by moderately heavy projectiles. The predictions of the theory for the relative probability of stripping to pickup reactions agree in general with the experimental data, and the degree of agreement increases with increasing number of transferred nucleons.

The (n, d) reactions on light nuclei

A survey of (n, d) reactions on 3He, 6Li, 7Li, 10B, 11B, 14N, 15N, 16O and 19F is made using zero-range DWBA calculations. Average parameters for the neutron and deuteron optical-model potentials are used. The spectroscopic factors obtained from this analysis are compared with theoretical predictions as well as with the results from other one-nucleon transfer reactions on these nuclei. In most cases reasonable agreement between theoretical predictions and experimental data is achieved. Strong disagreement for (n, d) reaction on 6Li is associated with the presence of reaction mechanisms other than proton pick-up.

Proton pick-up from the magnesium isotopes: 24, 25, 26Mg(d, τ)23, 24, 25Na

Abstract Energy spectra and angular distributions of the 3He particles from the (d, τ) reaction on 24, 25, 26Mg have been measured at Ed = 52 MeV with an energy resolution of about 80 keV. Excited states up to 11 MeV have been observed in 23Na. High-lying l = 1 transitions were excited by pick-up from the 1 p 3 2 shell. Discrepancies of 1p proton separation energies determined by quasi-free scattering and proton pick-up are discussed. The l-values have been determined for transitions to a variety of states with unknown spins in the doubly odd 24Na nucleus. A spin 5+ can be attributed to the 1.51 MeV level which is then the second member of the 4+ ground state rotational band. Several previously unknown spins could be determined in the 25Na level scheme. There is an apparent similarity in the proton-hole spectra of 23Na and 25Na and consequently a similar rotational structure. The spectra of 23Na, 24Na and 25Na are discussed in the framework of the Nilsson model. The spectroscopic factors are compared with shell-model calculations and predictions from a simple rotational model. States which are excited by pick-up from Nilsson orbit no. 7 contain approximately 75 % of the total sd strength. This contradicts the rotational model and requires strong band mixing. On the other hand the shell-model calculations account for excitation energies and spectroscopic factors of low-lying positive parity states. The data provide information about T = 1 and T = 3 2 states in mass-24 and mass-25 nuclei respectively.

Structure of Odd-AIndium Isotopes Determined by the (d,He3) Reaction

The nuclear structure of the odd-$A$ indium isotopes with masses 115, 117, 119, 121, and 123 has been studied using the proton pickup reaction Sn ($d$, $^{3}\mathrm{He}$) In with a deuteron bombarding energy of 28.9 MeV. Seven or more levels have been observed in each isotope. Excitation energies have been measured and $l$ values and spectroscopic factors have been extracted from the measured angular distributions. Ground-state $Q$ values have been measured relative to that for $^{116}\mathrm{Sn}$. The five ($d$, $^{3}\mathrm{He}$) spectra are quite similar. The ground state and levels at approximately 0.3 and 0.6 MeV in each nucleus are excited by pickup of a proton from the $1{g}_{\frac{9}{2}}$, $2{p}_{\frac{1}{2}}$, and $2{p}_{\frac{3}{2}}$ orbitals, respectively. These three levels contain approximately 70% of the ${g}_{\frac{9}{2}}$ sum-rule strength, 75% of the ${p}_{\frac{1}{2}}$ strength, and 50% of the ${p}_{\frac{3}{2}}$ strength. There is evidence for additional ${g}_{\frac{9}{2}}$ strength in $l=4$ transitions near 1.4 MeV in each isotope. The existence of these transitions can be explained by an admixture of the ${g}_{\frac{9}{2}}$ hole configuration with the ${\frac{9}{2}}^{+}$ member of the multiplet formed by coupling a ${g}_{\frac{9}{2}}$ hole to the collective ${2}^{+}$ state near 1.2 MeV in the tin core. Transitions to levels weakly excited near 1.0 MeV in $^{115}\mathrm{In}$, $^{117}\mathrm{In}$, and $^{119}\mathrm{In}$ are best reproduced with $l=2$ distorted-wave-approximation curves. If these levels are populated by a one-step $l=2$ direct reaction, it indicates a nonclosure of the $Z=50$ proton shell in the tin ground state. Surprisingly, no $l=3$ transitions corresponding to pickup of protons from the $1{f}_{\frac{5}{2}}$ orbital were observed, even though most of the isotopes were studied up to 3.5-MeV excitation.

Nuclear Data Sheets for A=208

Level schemes, spin and parity assignments, and decay properties are presented for all nuclei with mass number A=208. Experimental data and adopted values are given along with conclusions as to the spin and parity assignments. The presentation of the nuclear properties is given in the light of the data and current theoretical ideas. Where reasonably well established, shell-model configurations have been noted for many levels in 208Pb and 208Bi. Compilers have attempted to point out inconsistencies in the data and resolve the discrepancies when possible. No reaction data exist for 208Tl although this nucleus could be studied by 210Pb(d,a) since 210Pb targets have been fabricated. Although the levels in 208Pb have been studied in many ways, the neutron stripping and proton pickup data are not entirely satisfactory owing to either too low a bombarding energy or experimental resolution. There are no lifetime measurements for excited states in 208Bi except for an isomeric level. All tabulated C 2S and C 2S ′ direct-reaction strengths are derived from distorted-wave Born approximation reaction theory unless otherwise noted. The reader is referred to the invidual papers for details of these calculations as well as those regarding the analysis of decay of isobaric analog resonances.

Proton pick-up from 19F, 20Ne and 22Ne

Energy spectra and angular distributions of the 3He particles from the (d, 3He) reactions on 19F, 20Ne and 22Ne have been measured at an incident energy of 52 MeV. Excitation energies up to 15 MeV ( 18O), 7 MeV ( 19F) and 9 MeV ( 21F) and pick-up from seven different shell-model orbits have been observed. Several previously unknown negative parity states have been found in 18O. A ( 3 2 , 1 2 ) − level at 4.56 MeV was found in 19F, while the known J = 3 2 level at 3.91 MeV was not observed which suggests a positive parity assignment. The hole state spectrum of 21F resembles closely that of 19F. The spectroscopic factors are compared to the predictions from a simple rotational model and from various effective shell-model calculations. All models describe the positive parity transitions leading to 19, 21F reasonably well, but those leading to 18O are only understood by the inclusion of excited core contributions of 4p-2h character in 18O. The low-lying negative parity states, containing essentially the 1p 1 2 hole strengths, are also nicely described by the weak coupling calculations. Higher excited negative parity states show deviations which are discussed in terms of 2p particle-1p hole admixtures.

A study of proton hole states in [formula omitted] Nuclei by the (p, 2p) reaction at 46 MeV

Proton hole states in the 1 f 7 2 nuclei 46Ti, 54Fe, 56Fe, 58Ni and 60Ni have been studied using the (p, 2p) reaction with 46 MeV protons. The measured binding energies and angular correlations are consistent with the binding energies and orbital angular momentum assignments (1 f 7 2 , 2 s 1 2 and 1 d 3 2 ) obtained from proton pick-up reactions.