Recent Articles

Isospin-mixed ${}^{18}F$ states seen via ${}^{14}N (α, α_{1}) {}^{14}N$ (2.31 MeV)

L. C. Chen

Phys. Rev. C 14, 2069 (1976) - Published 1 December, 1976

Show Abstract

Extensive differential cross section measurements are reported for the isospin-forbidden reaction ${}^{14}N (α, α_{1}) {}^{14}N$ over the energy range $7.6 < E_{α} < 16.9$ MeV at 11 to 16 angles. A partial wave analysis with a new method of removing ambiguities and parametrizing $S$ matrix elements yields the level parameters of 151 isospin-mixed, natural-parity states in ${}^{18}F$ . These level parameters satisfactorily reproduce all the data. Many of these ${}^{18}F$ states correspond to those seen via ${}^{16}O (d, α_{1}) {}^{14}N$ . A number of levels have been identified as the analogs of $T = 1$ states in ${}^{18}O$ . Correlations in $S_{l} (E_{x})$ suggest intermediate structure and support Friedman's bridge state hypothesis.

NUCLEAR REACTIONS ${}^{14}N (α, α_{1})$ , $E = 7.6 - 16.9$ MeV; measured $σ (E, θ) : θ = 20 - 165 °$ , $Δ E = 20 - 30$ keV. Deduced ${}^{18}F$ level parameters, $S$ matrix analysis, new method excluding ambiguous solutions. Isospin mixing, deduced IAS.

Absolute normalization of ( $t, d$ ) and ( ${}^{3}{He}, d$ ) reactions

E. Friedman, A. Moalem, D. Suraqui, and S. Mordechai

Phys. Rev. C 14, 2082 (1976) - Published 1 December, 1976

Show Abstract

Parameters for the $d - p n$ , $t - d n$ , and ${}^{3}{He} - d p$ overlaps obtained from dispersion relations yield for the normalization constants for ( $d, p$ ), ( $t, d$ ), and ( ${}^{3}{He}, d$ ) reactions the values $D^{2} = (1.66, 3.9, and 2.9) \times 10^{4}$ ${MeV}^{2}$ ${fm}^{3}$ , respectively. These constants are employed in a comparative distorted-wave Born-approximation analysis of interrelated nucleon-transfer reactions on ${}^{40}{Ca}$ and ${}^{208}{Pb}$ at energies near the Coulomb barrier. The relative normalization of the ( $t, d$ ) and ( $d, p$ ) reactions is almost independent of the wave function of the transferred nucleon and of the optical potentials. For the mirror ( $t, d$ ) and ( ${}^{3}{He}, d$ ) reactions on a self-conjugate nucleus, the relative normalization depends on the ratio between root-mean-squared radii of the transferred nucleons. This ratio is calculated using a method which always yields the same relative normalization. Good consistency is found between reaction data and the normalization constants obtained from dispersion relations.

NUCLEAR REACTIONS ${}^{40}{Ca} (d, p_{0})$ , $E = 3, 4, and 6$ MeV. ${}^{40}{Ca} ({}^{3}{He}, d_{0}) {}^{41}{Sc}$ , $E = 9, 9.85, 10.7$ MeV. ${}^{40}{Ca} (d, {}^{3}{He}_{0}) {}^{39}K$ , $E = 11$ MeV. Measured $σ (E, θ)$ . Comparisons with ${}^{40}{Ca} (t, d_{0}) {}^{41}{Ca}$ , ${}^{208}{Pb} (d, t_{0, 1}) {}^{207}{Pb}$ , and ${}^{208}{Pb} (p, d_{0, 1}) {}^{207}{Pb}$ . Deduced normalization constants for ( $t, d$ ) and ( ${}^{3}{He}, d$ ) reactions.

${(f_{\frac{7}{2}})}^{- 3}$ configuration states in ${}^{45}{Ca}$

H. Nann, D. Mueller, and E. Kashy

Phys. Rev. C 14, 2089 (1976) - Published 1 December, 1976

Show Abstract

The ${}^{48}{Ca}$ ( ${}^{3}{He}$ , ${}^{6}{He}$ ) ${}^{45}{Ca}$ reaction has been studied at 70 MeV bombarding energy and angular distributions to strongly populated states in ${}^{45}{Ca}$ up to 5 MeV of excitation have been obtained. Evidence for ${(f_{\frac{7}{2}})}^{- 3}$ configuration states at 0.17, 1.43, 1.56, 1.89, and 2.88 MeV is discussed. The experimental ${(f_{\frac{7}{2}})}^{- 3}$ spectrum is compared with calculations based on the ${(f_{\frac{7}{2}})}^{- 2}$ spectrum of ${}^{46}{Ca}$ .

NUCLEAR REACTIONS ${}^{48}{Ca}$ ( ${}^{3}{He}$ , ${}^{6}{H e)}$ , $E_{3_{He}} = 70$ MeV, measured ( $E_{6_{He}}, θ$ ); enriched target, deduced excitation energies.

Nuclear spectroscopy of ${}^{189}{Os}$

Dirck Benson, Jr., Peter Kleinheinz, R. K. Sheline, and E. B. Shera

Phys. Rev. C 14, 2095 (1976) - Published 1 December, 1976

Show Abstract

Forty-three states have been observed up to an energy of 1474 keV in ${}^{189}{Os}$ using the reactions ${}^{188}{Os} (d, p) {}^{189}{Os}$ and ${}^{190}{Os} (d, t) {}^{189}{Os}$ , produced with 12 MeV deuterons, and the ${}^{188}{Os} (n, γ) {}^{189}{Os}$ reaction using thermal neutrons and observing $γ$ rays from 36 to 5933 keV. The neutron separation energy of ${}^{189}{Os}$ was determined to be 5920.8 ± 2.0 keV in agreement with the value of the ( $d, p$ ) reaction. The $Q$ value for the ${}^{190}{Os} (d, t) {}^{180}{Os}$ reaction was measured to be -1530 ± 4 keV. Using $l$ -transfer results, spin-parities were assigned to 14 states. A number of states up to 818 keV were qualiatively interpreted in terms of the Nilsson model. Anomalous Nilsson systematics particularly of the 1/2-[510] and 3/2-[512] bands involving anomalously large ( $d, p$ ) and ( $d, t$ ) cross sections populating the 5/2- and 3/2- states at 69.6 and 95.3 keV, respectively, are interpreted in terms of decreasing deformation and the consequent increase in Coriolis coupling. The low lying 5/2- state at 276 keV is interpreted as the lowest rotational state built on the 9/2-[505] level at 30.8 keV. This implies triaxiality for this configuration.

NUCLEAR REACTIONS ${}^{188}{Os} (d, p)$ , ${}^{190}{Os} (d, t)$ , $E = 12.0$ MeV, measured $σ (θ)$ , DWBA analysis; ${}^{188}{Os} (n_{th}, γ)$ ; deduced energies, $l$ , $j π$ of ${}^{189}{Os}$ levels. NUCLEAR STRUCTURE Nilsson model applied to ${}^{189}{Os}$ ; evidence for triaxiality.

Direct evidence for enhanced transient fields on fast ${}^{56}{Fe}$ ions recoiling through thin iron

M. Hass, J. M. Brennan, H. T. King, T. K. Saylor, and R. Kalish

Phys. Rev. C 14, 2119 (1976) - Published 1 December, 1976

Show Abstract

Results of ion-implantation perturbed-angular-correlation measurements on ${}^{56}{Fe}$ ions recoiling through magnetized Fe at high recoil energy ( $E_{R} \approx 56$ MeV) are reported. Angular shifts were measured using targets of various thicknesses for which the excited nuclei either stopped in or recoiled out of the iron. The results clearly establish the existence of enhanced transient fields acting on fast recoiling ions leaving the magnetized Fe foil and stopping in Cu. In such measurements the contributions from the static field and from the normal Lindhard-Winther field are eliminated. The possible use of this technique for measurements of magnetic moments of short-lived states is discussed. An experiment in which the ${}^{56}{Fe}$ ions recoiled into vacuum through the polarized foil was also carried out. In this case a strong attenuation of the angular correlation was observed; however, no excessive precession was seen, as would be observable if polarized hyperfine fields persisted in vacuum for a substantial part of the nuclear lifetime.

NUCLEAR REACTION ${}^{56}{Fe} ({}^{32}S, {}^{32}S^{'}) {}^{56}{Fe}^{*} (2^{+})$ , $E = 64$ MeV, targets of various thickness; measured $W (θ, H, \infty)$ in polarized iron. Deduced transient field of $Fe Fe$ at $\frac{v}{c} \approx 0.045$ . Demonstrated existence of enhanced transient fields.

Cross sections for the Ni, Cu, $Zn ({}^{16, 18}O, x n)$ reactions near the Coulomb barrier

R. L. Robinson, J. K. Bair, C. H. Johnson, P. H. Stelson, W. B. Dress, and C. M. Jones

Phys. Rev. C 14, 2126 (1976) - Published 1 December, 1976

Show Abstract

Cross sections for neutron emitting reactions induced by ${}^{16, 18}O$ bombardment of ${}^{58, 60, 61, 62, 64}{Ni}$ , ${}^{63, 65}{Cu}$ , and ${}^{64, 66, 67, 68, 70}{Zn}$ targets have been measured for projectile energies between 36 and 55 MeV by means of a large graphite sphere with embedded ${}^{10}{BF}_{3}$ detectors. Comparisons were made with the total reaction cross section calculated with (1) the optical model, (2) the sharp cutoff model, and (3) the parabolic-barrier model. The data are generally in good agreement with the optical-model predictions above the Coulomb barrier if the neutrons are assumed to be emitted statistically from a compound nucleus and if fusion is the predominant mechanism. Interaction barriers obtained from the parabolic-barrier model yield interaction radii with values of (1.54 to 1.65) ( $A_{T}^{\frac{1}{3}} + A_{P}^{\frac{1}{3}}$ ) fm.

NUCLEAR REACTIONS ${}^{58, 60, 61, 62, 64}{Ni}$ , ${}^{63, 65}{Cu}$ , ${}^{64, 66, 67, 68, 70}{Zn} ({}^{16, 18}O, x n)$ : $E = 36 - 55$ MeV. Measured total neutron yields.

Alpha transfer reaction ${}^{16}O$ ( ${}^{14}N$ , ${}^{10}B$ ) ${}^{20}{Ne}$ and high-spin states in ${}^{20}{Ne}$

K. Nagatani, C. W. Towsley, K. G. Nair, R. Hanus, M. Hamm, and D. Strottman

Phys. Rev. C 14, 2133 (1976) - Published 1 December, 1976

Show Abstract

The reaction ${}^{16}O$ ( ${}^{14}N$ , ${}^{10}B$ ) ${}^{20}{Ne}$ was studied at 155 MeV. The reaction mechanism shows characteristics of a direct $α$ transfer process with high-spin enhancement. Observed transitions are discussed in terms of high rotational bands, and high-spin members of the SU(3) (9,0) and (12,0) bands are assigned.

NUCLEAR REACTIONS ${}^{16}O$ ( ${}^{14}N$ , ${}^{10}B$ ), $E = 155$ MeV; ${}^{20}{Ne}$ deduced levels; semiclassical reaction model, SU(3) model; deduced rotational bands.

Gamma-ray multiplicities in evaporation residues formed in bombardments of ${}^{150}{Nd}$ by ${}^{20}{Ne}$

D. G. Sarantites, J. H. Barker, M. L. Halbert, D. C. Hensley, R. A. Dayras, E. Eichler, N. R. Johnson, and S. A. Gronemeyer

Phys. Rev. C 14, 2138 (1976) - Published 1 December, 1976

Show Abstract

The first three moments of the multiplicity distribution were deduced for the $γ$ -ray cascades in the evaporation residues produced in bombardments of ${}^{150}{Nd}$ with ${}^{20}{Ne}$ at four energies from 127.7 to 172.4 MeV by means of measurements of the first and higher order coincidence rates between a Ge(Li) spectrometer and eight NaI(T1) detectors. The cross sections for the production of ${}^{160 - 165}{Yb}$ and ${}^{156 - 161}{Er}$ were also measured. The average multiplicity $〈 M_{J} 〉$ and the width of the multiplicity distribution $σ_{M_{J}}$ for cascades via a state of spin $J$ were found to be independent of $J$ . For a given product, $〈 M 〉$ and $σ_{M}$ increase with bombardment energy but for fixed energy they decrease with increasing number of emitted neutrons. The observed values of $〈 M 〉$ and $σ_{M}$ range from 11 to 32 and 6 to 9, respectively. The multiplicities $〈 M 〉$ in the ( ${}^{20}{Ne}, x n α$ ) products are considerably lower than those for ( ${}^{20}{Ne}, x n$ ) but the widths $σ_{M}$ are the same for a given value of $x$ . The skewness of the multiplicity distribution is negative, approaching zero as the number of emitted neutrons increases. Angular momentum distributions were deduced (a) for each product prior to $γ$ decay and (b) for the initial compound nuclei which lead to each product. In each case these were found to overlap extensively for several neighboring neutron numbers. The $J$ distribution in ${}^{163}{Yb}$ extends up to $J ≃ 85$ prior to $γ$ decay. At the higher energies $α$ emission plays an important role in the deexcitation process by removing on the average an angular momentum of $\sim 10 ℏ$ . The present results suggest that $α$ emission follows neutron evaporation. The $J$ distributions obtained are compared with the predictions of the Bass model for fusing collisions. For the lower energies excellent agreement is observed. For the higher energies the Bass model prediction exceeds the measured $xn$ and $xn α$ cross sections at all $J$ , indicating that other exit channels account for an appreciable fraction of the fusion cross section.

NUCLEAR REACTIONS ${}^{150}{Nd} ({}^{20}{Ne}, x n γ)$ , ${}^{150}{Nd} ({}^{20}{Ne}, x n α γ)$ , $x = 5 - 10$ , $E = 127.7 - 172.4$ Mev; measured $σ (E, E_{γ})$ , $γ$ -ray multiplicities; deduced $J$ distributions in evaporation residues. Enriched target.

"Unique" energy-independent Woods-Saxon optical potential for ${}^{16}O$ + ${}^{28}{Si}$ elastic scattering

J. G. Cramer, R. M. DeVries, D. A. Goldberg, M. S. Zisman, and C. F. Maguire

Phys. Rev. C 14, 2158 (1976) - Published 1 December, 1976

Show Abstract

We have obtained new ${}^{16}O$ + ${}^{28}{Si}$ elastic scattering data at 215.2 MeV laboratory bombarding energy which show no evidence of strong rainbow scattering effects. We found that it is possible to simultaneously fit low and high energy data with the same energy-independent Woods-Saxon optical potential. We find that the imaginary potential for such fits is greater than or equal to the real potential in the surface region and that a marked preference is found for a real well depth of about 10 MeV, as determined in the region of the nuclear surface.

NUCLEAR REACTIONS ${}^{28}{Si}$ ( ${}^{16}O$ , ${}^{16}O$ ), $E_{L} = 215.2$ MeV measured $\frac{d σ}{d Ω} (θ)$ ; optical model analysis; deduced $\frac{W}{V}$ and energy-independent optical model parameters.

${}^{12}C$ + ${}^{14}N$ reaction at $E_{lab} = 53$ MeV

A. F. Zeller, M. E. Williams-Norton, R. J. Puigh, G. E. Moore, K. W. Kemper, and G. M. Hudson

Phys. Rev. C 14, 2162 (1976) - Published 1 December, 1976

Show Abstract

Angular distributions have been measured for the reactions ${}^{12}C$ ( ${}^{14}N$ , ${}^{9}{Be}$ ) ${}^{17}F$ , ${}^{12}C$ ( ${}^{14}N$ , ${}^{10}B$ ) ${}^{16}O$ , and ${}^{12}C$ ( ${}^{14}N$ , ${}^{12}C$ ) ${}^{14}N$ at $E_{14_{N}} = 53$ MeV, and compared to Hauser-Feshbach predictions. Additionally, excitation functions for ${}^{12}C$ ( ${}^{14}N$ , ${}^{6}{Li}$ ) ${}^{20}{Ne}$ and ${}^{12}C$ ( ${}^{14}N$ , ${}^{10}B$ ) ${}^{16}O$ in the region of 53 MeV have been taken. The reactions which involve ${}^{9}{Be}$ and ${}^{10}B$ are well fitted by the Hauser-Feshbach theory, indicating these products are formed via a compound nuclear reaction. The relative cross sections between the discrete states populated in ${}^{9}{Be}$ + ${}^{17}F$ and ${}^{10}B$ + ${}^{16}O$ are best described by a critical angular momentum between $14 and 15 ℏ$ . The magnitude of the ${}^{12}C$ ( ${}^{14}N$ , ${}^{12}C$ ) ${}^{14}N$ reaction is poorly described by Hauser-Feshbach theory, indicating a noncompound nature for this reaction channel.

NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{14}N$ , ${}^{6}{Li}$ ), ${}^{12}C$ ( ${}^{14}N$ , ${}^{9}{Be}$ ), ${}^{12}C$ ( ${}^{14}N$ , ${}^{10}B$ ), ${}^{12}C$ ( ${}^{14}N$ , ${}^{12}C$ ); measured $σ (θ)$ , $θ = 5 - 32.5 °$ , and 125-160°, $Δ θ = 2.5 °$ and $σ (E)$ , $E = 52.4 - 53.6$ MeV; deduced reaction mechanism. Natural targets. Hauser-Feshbach analysis.

Strongly damped heavy-ion collisions: Microscopic calculation of the kinetic-energy loss in rapid stretching

M. G. Mustafa

Phys. Rev. C 14, 2168 (1976) - Published 1 December, 1976

Show Abstract

The internal excitation energy of two colliding heavy ions is calculated in a microscopic model based on the rapid stretching of two rotating heavy ions in weak contact. The excitation energies are calculated for various projectile-target combinations ( ${}^{40}{Ar}$ , ${}^{84}{Kr}$ , and ${}^{136}{Xe}$ as projectiles and ${}^{209}{Bi}$ and ${}^{232}{Th}$ as targets). The calculated energies in the rapid stretching mode are shown to be consistent with the experimentally observed kinetic-energy loss in the strongly damped collisions. A more definite experimental test of the concept of rapid stretching of two colliding heavy ions is suggested.

NUCLEAR REACTIONS ${}^{40}{Ar}$ , ${}^{84}{Kr}$ , ${}^{136}{Xe}$ as projectiles and ${}^{209}{Bi}$ , ${}^{232}{Th}$ as targets; calculated kinetic-energy loss in strongly damped collisions.

Reaction dynamic dependences of ( ${}^{16}O$ , ${}^{15}N$ ) small angle cross sections

J. V. Maher, J. C. Peng, D. A. Sink, C. M. Cheng, H. S. Song, and T. J. Lewis

Phys. Rev. C 14, 2174 (1976) - Published 1 December, 1976

Show Abstract

Angular distributions have been measured for angles $θ_{lab} \geq 4 °$ for ( ${}^{16}O$ , ${}^{15}N$ ) transitions on $2 s - 1 d$ and $1 f - 2 p$ shell targets at bombarding energies $36 \leq E_{lab} \leq 53$ MeV. More than one transition has been studied for each $l$ value from 1 through 4 and the transition $Q$ values vary from nearly optimum to severely unfavored. A full-finite-range distorted-wave Born approximation analysis is successful in reproducing angular distribution shapes for transitions with bombarding energies well above the entrance channel Coulomb barrier, but such an analysis fails badly to fit angular distributions for lower bombarding energies, especially for unfavored $Q$ value transitions. There is some variation of the extracted absolute spectroscopic factors with bombarding energy, but in general the spectroscopic factors are in good agreement with ( ${}^{3}{He}, d$ ) results if the distorted-wave Born approximation predictions are normalized to the experimental cross sections at the grazing angle. The relative cross section contributions to the full distorted-wave Born approximation calculation from different $m$ substates are strongly dependent on $Q$ value and on small changes in optical potential parameters; the failures in the distorted-wave Born approximation analysis may arise from a miscalculation of the nuclear alignment.

NUCLEAR REACTIONS ${}^{26}{Mg}$ , ${}^{27}{Al}$ , ${}^{48, 50}{Ti}$ , ${}^{56}{Fe}$ , ${}^{62}{Ni}$ ( ${}^{16}O$ , ${}^{15}{N)}$ ; measured $σ (E, θ)$ ; DWBA analysis; enriched targets; $36 MeV \leq E \leq 53 MeV$ .

On-line mass-spectrometric measurement of rubidium and cesium isotopic distributions in ${}^{11}{B -}$ and ${}^{22}{N e - i n d u c e d}$ fission of ${}^{238}U$

M. de Saint-Simon, L. Lessard, W. Reisdorf, L. Remsberg, C. Thibault, E. Roeckl, R. Klapisch, I. V. Kuznetsov, Yu. Ts. Oganessian, and Yu. E. Penionshkevitch

Phys. Rev. C 14, 2185 (1976) - Published 1 December, 1976

Show Abstract

Using an on-line mass spectrometer we have measured isotopic distributions of rubidium and cesium in the fission of ${}^{238}U$ by ${}^{11}B$ (85 MeV) and ${}^{22}{Ne}$ (132 and 162 MeV).

NUCLEAR REACTIONS, FISSION ${}^{238}U ({}^{11}B, f)$ , ${}^{238}U ({}^{22}{Ne}, f)$ ; measured Rb, Cs isotopic distributions with mass spectrometer; deduced first moments, variances, structure.

Analysis of isotopic yield distributions in ${}^{11}{B -}$ and ${}^{22}{Ne}$ -induced fission of ${}^{238}U$

W. Reisdorf, M. de Saint-Simon, L. Remsberg, L. Lessard, C. Thibault, E. Roeckl, and R. Klapisch

Phys. Rev. C 14, 2189 (1976) - Published 1 December, 1976

Show Abstract

First moments and variances of measured rubidium and cesium isotopic distributions in the fission of ${}^{238}U$ by ${}^{11}B$ ( $E_{lab} = 85$ MeV) and ${}^{22}{Ne}$ ( $E_{lab} = 132 and 162$ MeV) are analyzed in the framework of the statistical model for nuclear fission and of evaporation theory. Excellent agreement with the data is obtained for ${}^{11}B$ -induced fission, assuming a compound-nuclear mechanism. The comparatively large isotopic variance observed in ${}^{22}{Ne}$ -induced fission can be explained if moderate contributions from fission following direct reactions are taken into account.

NUCLEAR REACTIONS, FISSION ${}^{238}U$ with heavy ions ( ${}^{11}B$ , ${}^{22}{Ne}$ ); isotopic distributions, calculated first moments, variances. Statistical model theory; good agreement with data; direct reaction contributions important.

Resonance ( $Δ Δ$ ) degrees of freedom in the deuteron and their influence on the electromagnetic form factors

M. Gari, H. Hyuga, and B. Sommer

Phys. Rev. C 14, 2196 (1976) - Published 1 December, 1976

Show Abstract

The influence of resonance ( $Δ$ ) contributions on the electromagnetic form factors of the deuteron is calculated. The deuteron wave functions including resonance ( $Δ Δ$ ) contributions are determined by a solution of six coupled equations. The effect of various baryon-baryon potentials is discussed. The numerically discussed deuteron electromagnetic form factors include also the meson-exchange contributions arising from $π$ , $ρ$ , and $ω$ pair currents as well as from the $ρ π γ$ current.

NUCLEAR REACTIONS ${}^{2}H (e, e^{'})$ , resonance admixtures, $\frac{d σ}{d Ω}$ calculated with meson-exchange corrections.

Pion-nucleus scattering and the Pauli principle

Carl B. Dover and R. H. Lemmer

Phys. Rev. C 14, 2211 (1976) - Published 1 December, 1976

Show Abstract

A density expansion of the pion self-energy for pions in nuclear matter is reexamined. It is shown that a single hole-line expansion of the self-energy (i) is equivalent to using a strongly quenched $π N$ scattering amplitude in the medium, and (ii) results in an inconsistent treatment of the virtual pions necessarily present in a field-theoretic description of the problem. Exchange of intermediate pions gives rise to nucleon-nucleon, as well as pion-nucleon scattering diagrams that both contribute to the pion self-energy in an essential way. The nucleon-nucleon scattering proceeds, for instance, via a one-pion-exchange potential that is, however, highly nonstatic for energy transfers between nucleons close to the incident energy. Such interactions are singled out automatically for special treatment in a field-theory approach to the problem, and should not be introduced in an ad hoc manner as part of an empirical $NN$ interaction in nuclear matter. We evaluate the coherent and charge exchange contributions to the pion-nucleus optical potential, proportional to the total density and the neutron-proton density difference, respectively. The Pauli principle is found to provide a small correction to the coherent part, both in the hole-line and density expansion formalisms. However, the charge exchange part of the potential is almost completely damped at low energies in the hole-line expansion, while the inclusion of backward-going graphs (random-phase-approximation correlations) restores it to its value based on free space $π N$ charge exchange amplitudes (i.e., no net Pauli effect).

NUCLEAR REACTIONS Compared density and hole line expansions for pion-nucleus optical potential; influence of Pauli principle on effective amplitude.

Model for the momentum distribution of baryon resonances in nuclei

M. Dillig

Phys. Rev. C 14, 2226 (1976) - Published 1 December, 1976

Show Abstract

The admixture of the $Δ (1232)$ in finite nuclei is calculated in first order perturbation theory. In the $Δ N$ transition potential $π$ and $ρ$ exchange is included, while the completeness relation is used to sum over intermediate $Δ N$ states. The results show that due to these effects the high momentum components in the $Δ$ wave function induced by the tensor force are reduced drastically, while the contribution from the spin term is enhanced significantly.

NUCLEAR STRUCTURE. Isobar momentum distribution; influence of $π$ , $ρ$ exchange, $NN$ correlations, nonstatic effects in the transition amplitude.

Pi-nucleon scattering

Gerald A. Miller

Phys. Rev. C 14, 2230 (1976) - Published 1 December, 1976

Show Abstract

In preparation for a field-theoretic treatment of $π$ -nucleus scattering, the corresponding $π$ -nucleon problem is examined. In order to include two-body input in the many-body problem it is useful to have a linear wave equation which describes $π$ -nucleon scattering. It is shown that the nonlinear Low equation, in the one-meson, one-nucleon truncation, may be expressed as a linear wave equation with an energy-dependent driving term interpretable as a potential. This potential includes the usual driving term of the Low equation plus an infinite set of higher order terms which incorporate the effects of crossing. A discussion of these terms and an iterative prescription for calculating them is given. In the static limit, our solution is shown to be equivalent to that of Chew and Low.

NUCLEAR REACTIONS Scattering theory, Low equation, $π$ -nucleon scattering.

Semirealistic shell-model interaction for neutron hole states in ${}^{208}{Pb}$

W. J. Baldridge and J. P. Vary

Phys. Rev. C 14, 2246 (1976) - Published 1 December, 1976

Show Abstract

The Brueckner $G$ matrix from the Reid soft-core potential is taken for the leading contribution to the effective two-neutron hole interaction in the ${}^{208}{Pb}$ region. To accomodate the corrections expected from core polarization and other higher order effects, including truncation of the model space, we add phenomenological two-body pairing and multipole forces whose strengths are determined by fitting the ${}^{206}{Pb}$ spectrum. A satisfactory fit is obtained with an interaction where the average total contribution of the added terms is less than 45% of the interaction. The same total effective interaction is then shown to yield a satisfactory spectrum for ${}^{204}{Pb}$ which may indicate the neglected effective many-body forces are not important. A comparison with the results of McGrory and Kuo is presented to examine the impact on the effective interaction of limiting the model space. We conclude the prospects are good for extending this approach to other nuclei below ${}^{208}{Pb}$ viewed as shell-model systems of valence holes in ${}^{208}{Pb}$ .

NUCLEAR STRUCTURE Shell-model structure of Pb isotopes; theory of shell-model effective interaction with phenomenological corrections; multipole potentials added to Brueckner reaction matrix.

Universal relationship connecting various two-body effective residual interactions

W. Knüpfer and M. G. Huber

Phys. Rev. C 14, 2254 (1976) - Published 1 December, 1976

Show Abstract

Starting from a momentum space analysis of the two-body matrix elements, a relation has been established between the size of the model space actually used in a specific calculation and the relevant properties of the effective residual interaction. It turns out that the two-body transition density acts like a filter function on the Fourier transform of the force; it exhibits a distinct structure which clearly reflects the size and the detailed properties of the configuration space actually used. From an investigation of this filter function an equivalence criterion for different effective residual two-body interactions has been established both for closed and open shell nuclei. This result can be used to construct simple although realistic effective forces. As an example, a model for a separable residual interaction is proposed in which the corresponding parameters are being clearly related to the nuclear radius (i.e., the mass number), to the quantum numbers (i.e., the angular momentum) of the state under consideration and to the size of the configuration space used. For a number of examples this force has been applied successfully for the description of low energy properties of both closed and open shell nuclei.

NUCLEAR STRUCTURE Effective residual interaction.

Select page:

Physical Review C

Recent Articles

Filter

Recent Issues

Isospin-mixed ${}^{18}F$ states seen via ${}^{14}N (α, α_{1}) {}^{14}N$ (2.31 MeV)

Absolute normalization of ( $t, d$ ) and ( ${}^{3}{He}, d$ ) reactions

${(f_{\frac{7}{2}})}^{- 3}$ configuration states in ${}^{45}{Ca}$

Nuclear spectroscopy of ${}^{189}{Os}$

Direct evidence for enhanced transient fields on fast ${}^{56}{Fe}$ ions recoiling through thin iron

Cross sections for the Ni, Cu, $Zn ({}^{16, 18}O, x n)$ reactions near the Coulomb barrier

Alpha transfer reaction ${}^{16}O$ ( ${}^{14}N$ , ${}^{10}B$ ) ${}^{20}{Ne}$ and high-spin states in ${}^{20}{Ne}$

Gamma-ray multiplicities in evaporation residues formed in bombardments of ${}^{150}{Nd}$ by ${}^{20}{Ne}$

"Unique" energy-independent Woods-Saxon optical potential for ${}^{16}O$ + ${}^{28}{Si}$ elastic scattering

${}^{12}C$ + ${}^{14}N$ reaction at $E_{lab} = 53$ MeV

Strongly damped heavy-ion collisions: Microscopic calculation of the kinetic-energy loss in rapid stretching

Reaction dynamic dependences of ( ${}^{16}O$ , ${}^{15}N$ ) small angle cross sections

On-line mass-spectrometric measurement of rubidium and cesium isotopic distributions in ${}^{11}{B -}$ and ${}^{22}{N e - i n d u c e d}$ fission of ${}^{238}U$

Analysis of isotopic yield distributions in ${}^{11}{B -}$ and ${}^{22}{Ne}$ -induced fission of ${}^{238}U$

Resonance ( $Δ Δ$ ) degrees of freedom in the deuteron and their influence on the electromagnetic form factors

Pion-nucleus scattering and the Pauli principle

Model for the momentum distribution of baryon resonances in nuclei

Pi-nucleon scattering

Semirealistic shell-model interaction for neutron hole states in ${}^{208}{Pb}$

Universal relationship connecting various two-body effective residual interactions

Filter

Recent Issues

Filter

Article Lookup

Enter a citation