Recent Articles

Level structure of ${}^{175}{Yb}$ and ${}^{177}{Yb}$ via the ${}^{174, 176}{Yb}$ ( $d$ , $p$ ) ${}^{175, 177}{Yb}$ and ${}^{176}{Yb}$ ( $d$ , $t$ ) ${}^{175}{Yb}$ reaction

R. W. Tarara and C. P. Browne

Phys. Rev. C 19, 674 (1979) - Published 1 March, 1979

Show Abstract

We studied ${}^{175}{Yb}$ with the ${}^{176}{Yb}$ ( $d$ , $t$ ) and ${}^{174}{Yb}$ ( $d$ , $p$ ) reactions and ${}^{177}{Yb}$ with the ${}^{176}{Yb}$ ( $d$ , $p$ ) reaction. We report 129 levels below 2550 keV in ${}^{175}{Yb}$ , 63 of which are previously unreported and 71 levels below 2700 keV in ${}^{177}{Yb}$ , 19 of which are new. We identified a few of these levels as possibly assigned to the wrong isotope because of isotopic contamination of the targets. The adopted 1104- and 1167-keV states in ${}^{177}{Yb}$ are among these identifications. We took angular distributions on all three reactions and compared the data to distorted-wave Born-approximation theory to extract $l$ values. The ( $d$ , $t$ ) distributions yield a few cases of anomalously shaped distributions, especially in the case of the 603.3-keV state in ${}^{175}{Yb}$ . The distribution data contradict a few tentative assignments and we can make several new $l$ assignments. Extensions of the proposed band structures of these nuclei suggest possible placements and spin assignments for a few additional states. We also show how the revised level schemes can be used to interpret data already in the literature.

NUCLEAR REACTIONS ${}^{174}{Yb}$ ( $d$ , $p$ ), ${}^{176}{Yb}$ ( $d$ , $t$ ), ${}^{176}{Yb}$ ( $d$ , $p$ ), $E (d) = 14$ MeV; measured excitation energies, $σ (p, θ)$ , $σ (t, θ)$ , $θ = 16 - 120 °$ , ${}^{175}{Yb}$ and ${}^{177}{Yb}$ deduced $l$ , $J$ , $π$ , $S$ ; enriched targets, DWBA analysis, magnetic spectrograph.

Simple unitary estimate for multistep processes

Stephen R. Cotanch

Phys. Rev. C 19, 693 (1979) - Published 1 March, 1979

Show Abstract

Utilizing the unitary constraint for an $N$ -dimensional $S$ matrix and phase averaging arguments, a simple expression is derived to provide realistic bounds on the exact multistep transition rate for the general reaction $A (a, b) B$ . The formula, which approximately includes a large class of multistep processes, is designed for practical upper estimates of cross section variation due to higher-order contributions from $N$ reaction channels. The result establishes model-independent guidelines for the importance of higher-order effects and represents a "sum rule" for multistep phenomena. Applications to the reactions ${}^{208}{Pb}$ ( $p$ , $t$ ) ${}^{206}{Pb}$ ( $3^{+}$ ) and ${}^{48}{Ca}$ ( ${}^{16}O$ , ${}^{15}C$ ) ${}^{49}{Ti}$ , which are improbable or forbidden in the one-step distorted-wave Born-approximation yields cross section estimates that are within order of magnitude agreement with observation.

NUCLEAR REACTIONS ${}^{40}{Ca}$ ( $d$ , $p$ ) ${}^{41}{Ca}$ , $E = 11$ MeV, ${}^{208}{Pb}$ ( $p$ , $t$ ) ${}^{206}{Pb}$ , $E = 35$ MeV, ${}^{48}{Ca}$ ( ${}^{16}O$ , ${}^{15}C$ ) ${}^{49}{Ti}$ , $E = 56$ MeV; calculate $σ (θ)$ . Phase averaging, unitary estimate of multichannel higher-order effects. Approximation of $N$ -dimensional $S$ matrix.

Charged-particle spectra: 90 MeV protons on ${}^{27}{Al}$ , ${}^{58}{Ni}$ , ${}^{90}{Zr}$ , and ${}^{209}{Bi}$

J. R. Wu, C. C. Chang, and H. D. Holmgren

Phys. Rev. C 19, 698 (1979) - Published 1 March, 1979

Show Abstract

Complete charged light-particle ( $Z \leq 2$ , $A \leq 4$ ) energy spectra were measured for 90 MeV protons on ${}^{27}{Al}$ , ${}^{58}{Ni}$ , ${}^{90}{Zr}$ , and ${}^{209}{Bi}$ and 100 MeV protons on ${}^{58}{Ni}$ . The energy spectra show a strong angular dependence and the spectral shapes at a given angle for the same particle type are similar in the high-energy continuum for all target nuclei. The non-equilibrium, charged light-particle yields show an $A^{\frac{1}{3}}$ dependence and are approximately given by $(200 \pm 10) A^{\frac{1}{3}}$ (mb). One striking feature is the similarity of the shapes of the $p$ , $d$ , and $t$ spectra, if the spectra are shifted by an appropriate binding energy. The relative intensity is approximately $p : d : t \frac{1 : 1}{\frac{10 : 1}{100}}$ at all angles. In the backward directions ( $θ \geq 140 °$ ) the spectra exhibit characteristic evaporation behavior with approximately the same slope for each target nucleus for a given observed particle. The slopes of the evaporation peaks (corresponding to a temperature of 2-3 MeV) for the different particle type are also rather similar. The experimental results were analyzed within the framework of the pre-equilibrium exciton model together with the evaporation theory. The pre-equilibrium exciton model using a 2p-1h initial configuration generally reproduces the experimental angle-integrated energy spectra reasonably well in shape, but underestimates especially the proton yield in the region of high-energy continuums.

NUCLEAR REACTION: ${}^{27}{Al}$ , ${}^{58}{Ni}$ , ${}^{90}{Zr}$ , ${}^{209}{Bi}$ ( $p$ , $xp$ ), ( $p$ , $xd$ ), ( $p$ , $xt$ ), ( $p$ , $x {}^{3}{He}$ ), ( $p$ , $x α$ ), $E_{p} = 90$ MeV; $θ_{L} = 20 ° - 40 °$ , ${}^{58}{Ni}$ ( $p$ , $xp$ ), ( $p$ , $xd$ ), ( $p$ , $xt$ ), ( $p$ , $x {}^{3}{He}$ ), ( $p$ , $x α$ ), $E_{p} = 100$ MeV; $θ_{L} = 15 ° - 155 °$ , measured $\frac{d^{2} σ}{d Ω d ε}$ , deduced $\frac{d σ}{d ε}$ and $σ (E)$ . Comparisons with preequilibrium exciton and evaporation models.

High-spin levels in ${}^{39}K$ excited by the ${}^{41}{Ca}$ ( $d$ , $α$ ) reaction

E. Sugarbaker, R. N. Boyd, D. Cline, P. B. Vold, J. R. Lien, and P. R. Goode

Phys. Rev. C 19, 714 (1979) - Published 1 March, 1979

Show Abstract

The ${}^{41}{Ca}$ ( $d$ , $α$ ) ${}^{39}K$ reaction has been used to investigate the low-lying high-spin states in ${}^{39}K$ . Conflicting spin assignments for the 5.719 MeV level in ${}^{39}K$ of $\frac{9}{2^{-}}$ or $\frac{13}{2^{-}}$ have been suggested in earlier studies. A 1p-2h model reproduces both the ${}^{41}{Ca}$ ( $d$ , $α$ ) ${}^{39}K$ and ${}^{39}K$ ( $α$ , $α^{'}$ ) ${}^{39}K$ reaction data leading to the high-spin states if the 5.719 MeV level is assumed to have a $J^{π}$ of $\frac{13}{2^{-}}$ . An alternate assignment of $J^{π} = \frac{9}{2^{-}}$ for this level is shown to produce very poor agreement with the model predictions.

NUCLEAR REACTIONS ${}^{41}{Ca}$ ( $d$ , $α$ ), $E = 22$ MeV, measured $σ (E_{α}, θ)$ , enriched target; DWBA analysis, deduced $L$ , $π$ ; 1p-2h model, deduced $J$ .

$g$ -factor of the $\frac{19}{2^{-}}$ isomer in ${}^{115}{Sb}$

S. R. Faber, L. E. Young, and F. M. Bernthal

Phys. Rev. C 19, 720 (1979) - Published 1 March, 1979

Show Abstract

The $g$ factor of the $t_{\frac{1}{2}} = 156$ nsec $\frac{19}{2^{-}}$ isomer in ${}^{115}{Sb}$ was measured by the time differential perturbed angular distribution technique using the reaction ${}^{115}{In}$ ( $a$ , $4 n$ ) ${}^{115}{Sb}$ . The measured value $g = + 0.287 (4)$ agrees with the structure ${[ν h_{\frac{11}{2}} \otimes ν d_{\frac{3}{2}} \otimes π d_{\frac{5}{2}}]}_{\frac{19}{2^{-}}}$ assuming additivity. The $g$ factor of the $\frac{11}{2^{-}}$ $t_{\frac{1}{2}} = 6.2$ ns state fed by the $\frac{19}{2^{-}}$ isomer decay was found to be + 1.06(10).

NUCLEAR REACTIONS ${}^{115}{In}$ ( $α$ , $4 n$ ), $E_{α} = 48$ MeV, pulsed beam, measured $I_{γ} (θ, B, t)$ for $E_{γ} = 1217, 1300$ keV, spin rotation; deduced $g_{\frac{19}{2^{-}}}$ , $g_{\frac{11}{2^{-}}}$ .

Fusion and nonfusion processes in reactions induced by 10-100-MeV ${}^{6}{Li}$ ions with Fe targets

J. Jastrzȩbski, H. Karwowski, M. Sadler, and P. P. Singh

Phys. Rev. C 19, 724 (1979) - Published 1 March, 1979

Show Abstract

Excitation functions and projected recoil ranges for radioactive nuclei produced in the ${}^{6}{Li}$ bombardment of ${}^{54}{Fe}$ an ${}^{56}{Fe}$ targets over 10 to 100 MeV energy range have been measured using the activation technique. At 55 and 85 MeV differential ranges have also been measured for the ${}^{56}{Fe}$ target. Using the in-beam gamma-ray technique production cross sections for many residual nuclei were measured for the ${}^{6}{Li}$ + ${}^{56}{Fe}$ system for a ${}^{6}{Li}$ energy range of 55 to 99 MeV. Close to 90% of the optical model reaction cross section is observed over the entire energy range. About 80% of the observed cross section corresponds to statistical evaporation of the compound nucleus. Above about 30 MeV ${}^{6}{Li}$ energy ${}^{56}{Fe}$ ( ${}^{6}{Li}$ , $α$ ) ${}^{58}{Co}$ transfer process can explain the observed behavior of recoil ranges. It contributes about 300 mb to the production of various nuclei reached through evaporation decay of ${}^{58}{Co}$ . Pre-equilibrium nucleon emission appears to be noticeable above 60 MeV and contributes 100 mb to the production process at 80 MeV. A reasonable account of the observed cross section for various product nuclei is given by the predictions of the fusion-evaporation model. In its fusion characteristics the ${}^{6}{Li}$ projectile appears to behave very much like other light heavy ions.

NUCLEAR REACTIONS ${}^{54}{Fe}$ ( ${}^{6}{Li}$ , $X$ ), ${}^{56}{Fe}$ ( ${}^{6}{Li}$ , $X$ ), $E = 10 - 100$ MeV. Measured $E γ$ , $I γ$ ; deduced $σ (X, E)$ , recoil ranges, $σ$ transfer, $σ$ pre-equilibrium nucleon emission, $σ$ fusion, mass distribution. Enriched targets, Ge(Li) counting, inbeam gamma-ray and radioactivity techniques.

Resonant heavy-ion elastic scattering from $s - d$ shell nuclei

R. Ost, M. R. Clover, R. M. DeVries, B. R. Fulton, H. E. Gove, and N. J. Rust

Phys. Rev. C 19, 740 (1979) - Published 1 March, 1979

Show Abstract

Angular distributions at angles $130 ° < θ_{cm} < 180 °$ have been measured for ${}^{12}C$ + ${}^{28}{Si}$ , ${}^{32}S$ , ${}^{40}{Ca}$ as well as ${}^{9}{Be}$ , ${}^{13}C$ + ${}^{28}{Si}$ in the energy range $20 MeV < E_{cm} < 35 MeV$ . Cross sections rising towards 180° are observed for all reactions. Excitation functions for the back angle enhancement show distinct structures, most pronounced for ${}^{12}C$ + ${}^{28}{Si}$ . Angular distributions for ${}^{12}C$ , especially those corresponding to peaks in the excitation function show oscillations of the type $P_{J}^{2} (cos θ)$ . The ${}^{12}C$ back angle enhancement decreases with target mass. Backscattering of the non- $α$ nuclei ${}^{9}{Be}$ and ${}^{13}C$ is reduced by about two orders of magnitude in comparison with ${}^{12}C$ . Standard theoretical approaches fail to explain all the observed effects.

NUCLEAR REACTIONS ${}^{12}C$ + ${}^{28}{Si}$ , ${}^{12}C$ + ${}^{32}S$ , ${}^{12}C$ + ${}^{40}{Ca}$ , ${}^{9}{Be}$ + ${}^{28}{Si}$ , ${}^{13}C$ + ${}^{28}{Si}$ , measured $σ (θ, E)$ elastic scattering, $130 ° < θ_{c . m .} < 180 °$ , $20 MeV < E_{c . m .} < 35 MeV$ , deduced $J^{π}$ of resonances.

Analyses of fusion reaction in light nuclei systems using various potentials

K. Nagatani and J. C. Peng

Phys. Rev. C 19, 747 (1979) - Published 1 March, 1979

Show Abstract

Fusion reactions of the neighboring nuclei systems, i.e., ${}^{12}C$ on ${}^{12}C$ , ${}^{14}N$ , ${}^{16}O$ , ${}^{18}O$ , and ${}^{19}F$ were analyzed. In the low energy regions, it is pointed out that a commonly used parametrized form has various insufficiencies. Use of the four kinds of potentials, Woods-Saxon, single-folding, double-folding, and proximity potentials were examined, and all show a unique trend of gradually increasing radii among these systems. In the high energy regions, decreasing cross sections towards higher incident energies cannot be explained in general by the staightforward yrast cut off treatments, although they are close in these light nuclei systems. If the partial waves are limited for those having the minima of their potential pockets inside the half density distance predicted by the proximity potential, the experimental data can be fitted.

NUCLEAR REACTIONS Analyses of fusion reactions: ${}^{12}C$ + ${}^{12}C$ , ${}^{12}C$ + ${}^{14}N$ , ${}^{12}C$ + ${}^{16}O$ , ${}^{12}C$ + ${}^{18}O$ , ${}^{12}C$ + ${}^{19}F$ ; potential model using Woods-Saxon, single-folding, double-folding potentials: yrast cutoff, critical distance in the proximity potential.

$α$ spectroscopic factors in ${}^{40}{Ca}$

H. T. Fortune, M. N. I. Al-Jadir, R. R. Betts, J. N. Bishop, and R. Middieton

Phys. Rev. C 19, 756 (1979) - Published 1 March, 1979

Show Abstract

In the ${}^{36}{Ar}$ ( ${}^{6}{Li}$ , $d$ ) ${}^{40}{Ca}$ reaction, at a bombarding energy of 17 MeV, angular distributions have been measured for all levels below 7 MeV excitation. Unnatural-parity states are weak. For natural-parity states, the angular distributions are characteristic of direct $α$ stripping, even as far backward as 160° for the strong states. The data have been analyzed with zero-range distorted-wave Born approximation in order to extract relative $α$ -particle spectroscopic factors.

NUCLEAR REACTIONS ${}^{36}{Ar}$ ( ${}^{6}{Li}$ , $d$ ), $E = 17.0$ MeV; measured $σ (E_{d}, θ)$ ; ${}^{40}{Ca}$ levels deduced $S_{α}$ . DWBA analysis. Enriched gas target.

Surface transparency in ${}^{12}C$ elastic scattering from ${}^{40, 42, 48}{Ca}$

T. R. Renner

Phys. Rev. C 19, 765 (1979) - Published 1 March, 1979

Show Abstract

Angular distributions between 3 and 110 degrees in the laboratory system were measured for the elastic scattering of ${}^{12}C$ from ${}^{40, 42, 48}{Ca}$ at 51.0, 49.9, and 47.2 MeV, respectively. Pronounced oscillations were observed in the ${}^{12}C$ + ${}^{40}{Ca}$ angular distribution. Weaker oscillations were observed in the ${}^{12}C$ + ${}^{42}{Ca}$ angular distributions while none were seen in ${}^{12}C$ + ${}^{48}{Ca}$ . An optical-model analysis was performed using Woods-Saxon and folded potentials. Surface transparent potentials were found to parametrize the oscillatory structure of the forward-angle data of ${}^{12}C$ + ${}^{40}{Ca}$ . Stronger surface absorption in the ${}^{12}C$ + ${}^{42, 48}{Ca}$ imaginary potentials apparently weakens or washes out any forward-angle oscillations. Optical potentials that fit forward-angle data of ${}^{12}C$ + ${}^{40}{Ca}$ also predict oscillatory structure in the excitation function at 180°.

NUCLEAR REACTIONS ${}^{40}{Ca}$ ( ${}^{12}C$ , ${}^{12}C$ ) ${}^{40}{Ca}$ , $E = 51$ MeV; measured $σ (θ)$ , measured $σ (E, θ = 180 °)$ . ${}^{42}{Ca}$ ( ${}^{12}C$ , ${}^{12}C$ ) ${}^{42}{Ca}$ , $E = 49.9$ MeV; ${}^{48}{Ca}$ ( ${}^{12}C$ , ${}^{12}C$ ) ${}^{48}{Ca}$ , $E = 47.2$ MeV; measured $σ (θ)$ .

Critical analysis of statistical methods used to detect resonances in nuclear reactions

L. C. Dennis, S. T. Thornton, and K. R. Cordell

Phys. Rev. C 19, 777 (1979) - Published 1 March, 1979

Show Abstract

The effectiveness of several existing statistical tests in locating resonances in compound nuclear reactions above the Coulomb barrier is examined, and a new test based on the number of maxima at any single bombarding energy in a set of excitation functions is introduced. It was found that only the three tests based on the deviation functions, summed cross sections, and the distribution of maxima were suitable for the detection of resonances, and that the latter test was the most sensitive. The various tests were used to analyze ${}^{12}C$ ( ${}^{12}C$ , $α$ ) ${}^{20}{Ne}$ , ${}^{12}C$ ( ${}^{14}N$ , $α$ ) ${}^{22}{Na}$ , and ${}^{12}C$ ( ${}^{15}N$ , $α$ ) ${}^{23}{Na}$ excitation functions. Evidence for nonstatistical structure was found in all three reactions by examining the distribution of maxima.

NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{12}C$ , $α$ ) ${}^{20}{Ne}$ , $E_{c . m .} = 18.0 - 25.5$ MeV; ${}^{12}C$ ( ${}^{14}N$ , $α$ ) ${}^{22}{Na}$ , $E_{c . m .} = 10.2 - 18.1$ MeV; ${}^{12}C$ ( ${}^{15}N$ , $α$ ) ${}^{23}{Na}$ , $E_{c . m .} = 9.5 - 17.3$ MeV. Statistical model predictions. Statistical tests examined. Nonstatistical structure observed.

Enhancements in the $p$ and $d$ exit channels of ${}^{12}C$ + ${}^{12}C$ : $E_{c . m .} ≃ 14.3 and 25.2$ MeV

A. H. Lumpkin, L. H. Harwood, J. D. Fox, and K. W. Kemper

Phys. Rev. C 19, 785 (1979) - Published 1 March, 1979

Show Abstract

The enhanced yields of high spin states populated in the $p$ and $d$ exit channels for ${}^{12}C$ + ${}^{12}C$ reactions are utilized for particle- $γ$ coincidence measurements at $E_{c . m .} ≃ 14.3 and 25.2$ MeV. The ( ${}^{12}C$ , $p γ$ ) results at $E_{c . m .} ≃ 14.3$ MeV support the $\frac{15}{2^{+}}$ assignment to the $E_{x} = 9.80$ MeV state. The ( ${}^{12}C$ , $d γ$ ) results at $E_{c . m .} ≃ 25.2$ MeV show an enhanced 9.77 MeV ( $9^{+}$ ) state to have a strong $γ$ -ray branch to the $E_{x} = 4.52$ MeV ( $7^{+}$ ) state.

NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{12}C$ , $p γ$ ), $E_{c . m .} ≃ 14.3$ MeV; measured $E_{p}$ , $E_{γ}$ , $p - γ$ coin; ${}^{12}C$ ( ${}^{12}C$ , $d γ$ ), $E_{c . m .} \approx 25.2$ MeV measured $E_{d}$ , $E_{γ}$ , $d - γ$ coin.

${}^{28}{Si}$ + ${}^{28}{Si}$ reactions

L. R. Medsker, L. V. Theisen, L. H. Fry, Jr., and J. S. Clements

Phys. Rev. C 19, 790 (1979) - Published 1 March, 1979

Show Abstract

Evaporation residues from ${}^{28}{Si}$ -induced reactions on ${}^{28}{Si}$ from 65-90 MeV have been studied by means of $γ$ -ray spectroscopy. High spin states of the residual nuclei have been observed, and the yields of residual nuclei resulting from three particle removal from the initial compound nucleus ${}^{56}{Ni}$ are dominant. Experimental relative production cross sections of the residual nuclei are compared to evaporation-model calculations.

NUCLEAR REACTION ${}^{28}{Si}$ ( ${}^{28}{Si}$ , $X γ$ ) at $E_{lab} = 65 - 90$ MeV. $σ (E_{γ}, E)$ , $σ (E_{γ}, θ)$ , and $γ γ$ coin. Deduced reaction cross sections. Ge(Li) detectors.

Elastic and inelastic scattering of ${}^{16}O$ and ${}^{18}O$ on ${}^{28}{Si}$ at 56 MeV incident energy

M. C. Mermaz, M. A. G. Fernandes, A. Greiner, B. T. Kim, and N. Lisbona

Phys. Rev. C 19, 794 (1979) - Published 1 March, 1979

Show Abstract

Elastic and inelastic scatterings of ${}^{16}O$ and ${}^{18}O$ projectiles have been studied on ${}^{28}{Si}$ nucleus at 56 MeV incident energy. Optical model and coupled-channel analyses have been performed in order to define the nature of the optical potential. It has turned out that the enhanced backward angle oscillations that appeared in the angular distribution for the ${}^{16}O$ scattering are mainly due to refractive phenomena namely orbiting rather than diffractive phenomena. The potential necessary to reproduce the experimental data has to be surface transparent for ${}^{16}O$ projectile, with a pocket in the effective potential in the grazing wave region and with a sharp diffusivity in the imaginary part in order to produce a mirror effect due to strong and abrupt volume absorption. On the other hand the potential necessary to fit the ${}^{18}O$ scattering angular distributions is just a normal strong absorptive potential. The absence of any surface transparency in the case of ${}^{18}O$ scattering can be attributed to the fact that many direct reaction channels are well $Q$ matched.

NUCLEAR REACTIONS ${}^{28}{Si}$ ( ${}^{16}O$ , ${}^{16}O$ ) and ${}^{28}{Si}$ ( ${}^{18}O$ , ${}^{18}O$ ), $E_{{}^{16}O}$ , $E_{{}^{18}O} = 56$ MeV; elastic and inelastic angular distributions measured between 5° and 71° (lab). Optical model and coupled-channel analysis.

Low energy one-neutron transfer reactions between heavy ions

Mahir S. Hussein

Phys. Rev. C 19, 807 (1979) - Published 1 March, 1979

Show Abstract

A constraint is imposed on the possible value of the diffusivity of the imaginary part of the optical model potential used to fit elastic scattering data of light heavy ions at sub-barrier energies. This is done by fixing the center of mass energy at which the optimal - $Q$ - value one-neutron-transfer $S$ factor crosses the fusion $S$ factor.

NUCLEAR REACTIONS Sub-Coulomb one-neutron transfer between heavy ions discussed.

High-spin states of negative parity in ${}^{69}{Ge}$

V. Zobel, L. Cleemann, J. Eberth, W. Neumann, and N. Wiehl

Phys. Rev. C 19, 811 (1979) - Published 1 March, 1979

Show Abstract

The nucleus ${}^{69}{Ge}$ has been studied through the reaction ${}^{55}{Mn}$ ( ${}^{16}O$ , $pn γ$ ) ${}^{69}{Ge}$ at $E_{{}^{16}O} = 44$ MeV. New levels above 3 MeV excitation energy have been found and properties of these states have been assigned from investigations of prompt $γ$ rays using different in-beam $γ$ -spectroscopic techniques such as angular distributions, $γ γ$ coincidences, yield function, lifetime measurements, and linear polarization. No experimental evidence has been found for collective bands based on the $\frac{15}{2^{+}}$ , $\frac{17}{2^{+}}$ doublet at 2483 keV. The nucleus entirely decays through a negative parity band of fairly long living states above 3 MeV. Similar patterns have been found earlier in the neighboring even Ge isotopes as well as in some even Zn isotopes. A speculative description of the negative parity states in terms of a few-neutron excitation associated with $ν (1 f_{\frac{5}{2}}, 1 g_{\frac{9}{2}})$ configurations is attempted.

NUCLEAR REACTIONS ${}^{55}{Mn}$ ( ${}^{16}O$ , $pn γ$ ) ${}^{69}{Ge}$ , $E = 40 - 51$ MeV; measured $E_{γ}$ , $I_{γ}$ , $γ - γ$ coincidences, $σ (θ_{γ})$ , linear polarization, relative excitation function, lifetimes (RDM); deduced $E_{X}$ , $I^{π}$ , $T_{\frac{1}{2}}$ , $B (M λ)$ and $γ$ -mixing ratios. Natural target. Ge (Li) detectors.

Abrasion-ablation calculations of large fragment yields from relativistic heavy ion reactions

Luiz F. Oliveira, Raul Donangelo, and John O. Rasmussen

Phys. Rev. C 19, 826 (1979) - Published 1 March, 1979

Show Abstract

Calculations of large mass fragment yields from high-energy heavy-ion reactions are performed based on the abrasion-ablation model. The geometrical picture of the clean-cut fireball model is used to calculate the number of participant nucleons in the abrasion stage and the excitation energy of the spectators (primary residues). A standard statistical evaporation code is used to calculate the ablation stage. Results from this model show an overall agreement with experimental data, although some systematic discrepancies are found and discussed. A frictional spectator interaction is introduced which increases the average excitation energy of primary fragments and improves the results considerably.

NUCLEAR REACTIONS Relativistic Heavy-ions, abrasion-ablation model, peripheral reactions, calculated fragmentation cross sections.

Semiclassical description of two-nucleon transfer between superfluid nuclei

H. Weiss

Phys. Rev. C 19, 834 (1979) - Published 1 March, 1979

Show Abstract

Two-nucleon transfer reactions between superfluid nuclei are treated in the formalism of Dietrich and Hara starting from a microscopic Hamiltonian in second quantization. Amplitudes for simultaneous and successive transfer of neutron pairs between tin isotopes are calculated in perturbation theory. Nonorthogonality effects are numerically estimated. The possibility of a nuclear Josephson effect is predicted just below the barrier.

NUCLEAR REACTIONS ${}^{120}{Sn}$ ( ${}^{120}{Sn}$ , ${}^{118}{Sn}$ ) ${}^{122}{Sn}$ , semiclassical approx., calculated pair transfer amplitudes, nucl. Josephson effect.

Optical potential for nucleus-nucleus systems

A. K. Jain and C. S. Shastry

Phys. Rev. C 19, 848 (1979) - Published 1 March, 1979

Show Abstract

The electrostatic and nuclear parts of the nucleus-nucleus optical potential are constructed using the double folding model by taking into account nuclear charge and matter distributions, along with a suitably chosen effective nucleon-nucleon interaction. For nuclei with uniform charge distributions, a closed form expression for the electrostatic potential has been obtained earlier. This is found to be a very good approximation to the electrostatic potential corresponding to commonly known realistic charge distributions. Optical model calculations for the ${}^{16}O$ - ${}^{16}O$ system using this improved electrostatic potential are reported which provide a slightly better fit to elastic scattering data. The six dimensional integral for the nuclear part of the optical potential is reduced to a three dimensional integral for the case of spherically sysmmetric density distributions and this leads to substantial reduction in computations. In contrast with the electrostatic part, it is found that the nuclear part of the optical potential is quite sensitive to the shape of the density distributions. The optical potential constructed by the "double folding" method with only a single adjustable parameter corresponding to the strength of the imaginary part, is used to fit successfully ${}^{12}C$ - ${}^{12}C$ scattering data at $E_{lab} = 102.1$ MeV.

NUCLEAR REACTIONS Optical model for nucleus-nucleus system, double folding model, realistic electrostatic potentials.

Energy and angular correlation of He ions and heavy fragments in 11.5-GeV proton bombardment of uranium

B. D. Wilkins, E. P. Steinberg, and S. B. Kaufman

Phys. Rev. C 19, 856 (1979) - Published 1 March, 1979

Show Abstract

Measurements of the number and kinetic energy distribution of He ions formed in the 11.5-GeV proton bombardment of uranium were made with a particle telescope as a function of the angle between the He ion and the direction of a heavy fragment. The mass of the latter was determined in a time-of-flight system. No correlation in the intensity or energy of He ions with the direction of the heavy fragment was observed. This is interpreted as an indication that the He ions are formed prior to or simultaneously with the formation of the heavy fragments rather than being evaporated from an excited, fully accelerated fragment. In the case of fission fragments these results provide direct evidence that fission does not occur as a prominent process at high excitation energy ( $E^{*}$ ), but rather, is essentially a low energy phenomenon. Current formulations of $\frac{Γ_{f}}{Γ_{n}}$ predict a large proportion of fission at high $E^{*}$ for the nuclides involved here, in disagreement with the results of the present experiment. An estimate is made of the relative deposition energy involved in the reactions as a function of the energy and mass of the heavy fragment formed. This clearly shows that the region of $30 ≲ A ≲ 70$ is associated with the highest deposition energy. This is just the region of the so-called "fragmentation" products whose recoil properties provide evidence for the existence of a specific high-energy reaction mechanism.

NUCLEAR REACTIONS, FISSION ${}^{238}U$ ( $p$ , He and heavy fragments), $E_{p} = 11.5$ GeV; measured energy and angular correlation of He and heavy fragments; compare deduced $\frac{Γ_{f}}{Γ_{n}}$ with theory; identify product masses associated with highest deposition energy.

Select page:

Physical Review C

Recent Articles

Filter

Recent Issues

Level structure of ${}^{175}{Yb}$ and ${}^{177}{Yb}$ via the ${}^{174, 176}{Yb}$ ( $d$ , $p$ ) ${}^{175, 177}{Yb}$ and ${}^{176}{Yb}$ ( $d$ , $t$ ) ${}^{175}{Yb}$ reaction

Simple unitary estimate for multistep processes

Charged-particle spectra: 90 MeV protons on ${}^{27}{Al}$ , ${}^{58}{Ni}$ , ${}^{90}{Zr}$ , and ${}^{209}{Bi}$

High-spin levels in ${}^{39}K$ excited by the ${}^{41}{Ca}$ ( $d$ , $α$ ) reaction

$g$ -factor of the $\frac{19}{2^{-}}$ isomer in ${}^{115}{Sb}$

Fusion and nonfusion processes in reactions induced by 10-100-MeV ${}^{6}{Li}$ ions with Fe targets

Resonant heavy-ion elastic scattering from $s - d$ shell nuclei

Analyses of fusion reaction in light nuclei systems using various potentials

$α$ spectroscopic factors in ${}^{40}{Ca}$

Surface transparency in ${}^{12}C$ elastic scattering from ${}^{40, 42, 48}{Ca}$

Critical analysis of statistical methods used to detect resonances in nuclear reactions

Enhancements in the $p$ and $d$ exit channels of ${}^{12}C$ + ${}^{12}C$ : $E_{c . m .} ≃ 14.3 and 25.2$ MeV

${}^{28}{Si}$ + ${}^{28}{Si}$ reactions

Elastic and inelastic scattering of ${}^{16}O$ and ${}^{18}O$ on ${}^{28}{Si}$ at 56 MeV incident energy

Low energy one-neutron transfer reactions between heavy ions

High-spin states of negative parity in ${}^{69}{Ge}$

Abrasion-ablation calculations of large fragment yields from relativistic heavy ion reactions

Semiclassical description of two-nucleon transfer between superfluid nuclei

Optical potential for nucleus-nucleus systems

Energy and angular correlation of He ions and heavy fragments in 11.5-GeV proton bombardment of uranium

Filter

Recent Issues

Filter

Article Lookup

Enter a citation