Recent Articles

Some properties of projected three-body theories of deuteron-nucleus collisions

N. Austern

Phys. Rev. C 25, 2827 (1982) - Published 1 May, 1982

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Three-body theories of deuteron-nucleus collisions, based on limited sets of relative angular momenta, are discussed as projected components within a more complete theory. It is argued that the extension to the more complete theory is well behaved and that the previous truncations are reasonable. Possible tests are considered.

NUCLEAR REACTIONS Scattering theory, deuteron-nucleus, angular-momentum projected three-body theory.

Determination of the $NN$ cross section in nuclei from inclusive ( $π$ , $π^{'}$ ) and coincidence ( $π$ , $π N$ ) reactions

E. Piasetzky, Richard R. Silbar, and Morton M. Sternheim

Phys. Rev. C 25, 2830 (1982) - Published 1 May, 1982

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A semiclassical model applied to backward inelastic pion-nucleus scattering reproduces the general features of the ( $π$ , $π^{'}$ ) data and suggests a way of extracting the fractions involving pion multiple scattering, nucleon final state interactions, and unperturbed quasifree scattering. In order to fit the knockout ( $π^{+}$ , $π^{+} p$ ) coincidence data, the free $NN$ cross sections must be reduced by a factor which rapidly increases with $A$ , implying a long mean free path for the outgoing nucleon in heavy nuclei.

NUCLEAR REACTIONS Inclusive ( $π$ , $π^{'}$ ) and coincidence ( $π$ , $π N$ ) in C, Al, Fe, Nb, Bi; calculated semiclassically. Reduced $NN$ cross section in nuclei.

Particle-hole ambiguity in the parameters of the microscopic interacting boson model

S. Pittel, P. D. Duval, and B. R. Barrett

Phys. Rev. C 25, 2834 (1982) - Published 1 May, 1982

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The parameters of the microscopic interacting boson model that emerge from a multi-nondegenerate-orbit theory are shown to depend on whether they are generated in terms of correlated pairs of particles or correlated pairs of holes. It is suggested that the ambiguity results from the shell-model truncation inherent in the interacting boson model and that it can be alleviated by including renormalization effects from outside the interacting boson model subspace.

NUCLEAR STRUCTURE Microscopic interacting boson model; particle-hole ambiguity in model parameters.

Simple formula for the ground band spectrum of even-mass rotational nuclei

A. Partensky and C. Quesne

Phys. Rev. C 25, 2837 (1982) - Published 1 May, 1982

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The increase of the moment of inertia with angular momentum predicted in the U(6) ⊃ SU(3) model is combined with the axial rotor formula to produce a new one-parameter formula for the ground band spectrum of even-mass rotational nuclei. Good agreement with experimental spectra is obtained in many cases, especially in the actinide region.

NUCLEAR STRUCTURE Even-mass rotational nuclei; calculated ground band energies. New one-parameter formula.

Pion charge-exchange reaction and transition densities to isobaric analog states

N. Auerbach and A. Yeverechyahu

Phys. Rev. C 25, 2841 (1982) - Published 1 May, 1982

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Distorted wave impulse approximation calculations were performed for the ( $π^{+}$ , $π^{0}$ ) reaction to isobaric analog resonances in a series of nuclei employing two types of transition densities. The calculations are sensitive to the types of transition densities used, giving substantially different cross sections in the two cases.

NUCLEAR STRUCTURE Pion charge exchange to isobaric analog states.

Intermediate structure of the ${}^{12}C$ + ${}^{12}C$ system

S. Y. Lee, H. W. Wilschut, and R. Ledoux

Phys. Rev. C 25, 2844 (1982) - Published 1 May, 1982

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We show that the ${}^{12}C$ + ${}^{12}C$ elastic angular distribution can be described very well with an $S$ matrix obtained from a deep optical potential to which resonance is added. We interpret these resonances as bound states embedded in a continuum. Their effect on the total reaction cross section is also discussed.

NUCLEAR REACTIONS Resonances in heavy ion scattering.

Mass of ${}^{197}{Hg}$

G. Berrier-Ronsin, M. Vergnes, G. Rotbard, J. Vernotte, S. Fortier, J. M. Maison, and R. Tamisier

Phys. Rev. C 25, 2848 (1982) - Published 1 May, 1982

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The peak corresponding to the ground state of ${}^{197}{Hg}$ , in the ${}^{199}{Hg}$ ( $p$ , $t$ ) ${}^{197}{Hg}$ reaction at 25 MeV, has been observed both with natural Hg and with a separated ${}^{199}{Hg}$ target. The determined $Q$ value, $Q = - 6658 \pm 8$ keV, disagrees with previous measurements.

NUCLEAR REACTIONS ${}^{199}{Hg}$ ( $p$ , $t$ ) ${}^{197}{Hg}$ , $E = 25$ MeV; $Q$ value measured, mass excess inferred.

Erratum: Fusion behavior in time-dependent Hartree-Fock calculations of ${}^{86}{Kr}$ + ${}^{139}{La}$ and ${}^{84}{Kr}$ + ${}^{209}{Bi}$ collisions

K. T. R. Davies, K. R. Sandhya Devi, and M. R. Strayer

Phys. Rev. C 25, 2850 (1982) - Published 1 May, 1982

Erratum: ${}^{92, 94, 97, 98}{Mo}$ ( $t$ , $p$ ) reactions at $E_{t} = 17$ MeV

E. R. Flynn, F. Ajzenberg-Selove, Ronald E. Brown, J. A. Cizewski, and J. W. Sunier

Phys. Rev. C 25, 2850 (1982) - Published 1 May, 1982

Erratum: Proton hole states in neutron rich nuclei near $A = 100$

E. R. Flynn, F. Ajzenberg-Selove, Ronald E. Brown, J. A. Cizewski, and J. W. Sunier

Phys. Rev. C 25, 2851 (1982) - Published 1 May, 1982

Erratum: Unusual phenomena in fireball

R. K. Tripathi

Phys. Rev. C 25, 2853 (1982) - Published 1 May, 1982

Erratum: Effect of center-of-mass correlations and intermediate states on $π$ - ${}^{3}{He}$ scattering

J. P. Mestre, W. J. Gerace, and D. A. Sparrow

Phys. Rev. C 25, 2853 (1982) - Published 1 May, 1982

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Spin-orbit deformations deduced from analyzing powers for inelastic neutron scattering from ${}^{54}{Fe}$ , ${}^{56}{Fe}$ , ${}^{58}{Ni}$ , ${}^{60}{Ni}$ , ${}^{120}{Sn}$ , and ${}^{208}{Pb}$

P. P. Guss, C. E. Floyd, K. Murphy, C. R. Howell, R. S. Pedroni, G. M. Honore, H. G. Pfutzner, G. Tungate, R. C. Byrd, R. L. Walter, and J. P. Delaroche

Phys. Rev. C 25, 2854(R) (1982) - Published 1 May, 1982

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Analyzing powers $A_{y} (θ)$ for inelastic scattering of 10-MeV neutrons to the first excited states of ${}^{54}{Fe}$ , ${}^{56}{Fe}$ , ${}^{58}{Ni}$ , ${}^{60}{Ni}$ , ${}^{120}{Sn}$ , and ${}^{208}{Pb}$ have been measured at a few selected angles. These data were analyzed using a coupled channels code in which the full Thomas form of the spin-orbit potential is assumed. The magnitudes of the observed spin-orbit deformations, which were found to be similar to those of ( $p$ , $p^{'}$ ) in each case, contradict recent suggestions based on microscopic nuclear structure considerations.

NUCLEAR REACTIONS ${}^{54, 56}{Fe}$ , ${}^{58, 60}{Ni}$ , ${}^{120}{Sn}$ , ${}^{208}{Pb}$ ( $\vec{n}$ , $n^{'}$ ) $E_{n} = 10$ MeV; measured $A_{y} (θ)$ ; deduced $\frac{δ_{so}}{δ_{c}}$ .

RAPID COMMUNICATION

Microscopic determination of the interacting boson model parameters

Y. K. Gambhir, P. Ring, and P. Schuck

Phys. Rev. C 25, 2858(R) (1982) - Published 1 May, 1982

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A general microscopic procedure for determining the interacting boson model parameters is presented. A set of correlated fermion coupled pair operators is generated using an approximate seniority shell model. With Marumori mapping the boson images corresponding to $s$ and $d$ are constructed and the interacting boson model parameters determined. The shell effects do show up in our calculation specially at the beginning and at the end of the 50-82 shell. The calculated interacting boson model parameters agree well with the corresponding phenomenologically determined values.

NUCLEAR SPECTROSCOPY Interacting boson model, microscopic boson theory, broken pair approximation, shell effects.

RAPID COMMUNICATION

Effects of averaging on energy dependence of backward-angle heavy-ion cross sections: Calculations of "de-averaged" excitation functions

W. E. Frahn and S. K. Kauffmann

Phys. Rev. C 25, 2862(R) (1982) - Published 1 May, 1982

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The averaging over a small angular range involved in the measurement of "180° excitation functions" for heavy-ion scattering is shown to have a drastic effect on the energy dependence of the backward-angle cross sections. A simple analytic method is described by which the measured data can be de-averaged to determine the "true" 180° excitation functions.

NUCLEAR REACTIONS 180° excitation functions for heavy-ion scattering; effects of and corrections for angle averaging.

Analyzing power for the ${}^{16}O$ ( $\vec{p}$ , $n$ ) ${}^{16}F$ ( $4^{-}$ ,6.37 MeV) reaction at 134 MeV

R. Madey, A. Fazely, B. D. Anderson, A. R. Baldwin, A. M. Kalenda, R. J. McCarthy, P. C. Tandy, J. W. Watson, W. Bertozzi, T. Buti, M. Finn, M. Kovash, B. Pugh, and C. C. Foster

Phys. Rev. C 25, 1715 (1982) - Published 1 April, 1982

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We measured the analyzing power for the ${}^{16}O$ ( $\vec{p}$ , $n$ ) ${}^{16}F$ ( $4^{-}$ ,6.37 MeV) reaction at 134.0 MeV and the differential cross section for the same reaction at 135.2 MeV. The shape of the cross section for the transition to this unnatural parity stretched state is described well by a distorted-wave impulse-approximation calculation using a ${(π d_{\frac{5}{2}}, ν {p_{\frac{3}{2}}}^{- 1})}_{4^{-}}$ configuration and the effective interaction derived by Love and Franey from nucleon-nucleon phase shifts. The analyzing power from this calculation reproduces all of the qualitative features of the data and supports the use of the impulse approximation as an excellent starting point for describing the reaction mechanism. Quantitative agreement between the experimental and theoretical analyzing power can be improved by eliminating the imaginary tensor term of this interaction and taking the real part to be that derived by Love from the Sussex matrix elements. The sensitivity of the calculations to the choice of optical potentials and the importance of spin-orbit distortion is explored.

NUCLEAR REACTIONS ${}^{16}O$ ( $\vec{p}$ , $n$ ) ${}^{16}F$ , $E = 134$ MeV; measured neutron spectra at 12 angles between $θ = 0 ° and 62.9 °$ ; extracted $σ (θ)$ and $A (θ)$ to $J^{π} = 4^{-}, 6.37$ MeV state of ${}^{16}F$ . Compared angular distributions of $σ (θ)$ and $A (θ)$ with calculations based on a nucleon-nucleon effective interaction.

Direct-reaction model for ( $p$ , $γ$ ) reactions to highly excited states in ${}^{12}C$

J. T. Londergan and L. D. Ludeking

Phys. Rev. C 25, 1722 (1982) - Published 1 April, 1982

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Proton radiative capture reactions on ${}^{11}B$ targets are calculated assuming a direct capture mechanism. This is used to predict ( $p$ , $γ$ ) transitions leading to the ground state of ${}^{12}C$ , and to high-lying excited states at about 19 MeV excitation in ${}^{12}C$ . The results are compared with recent experimental data. The theoretical cross sections are the same magnitude as the data, but do not properly reproduce the energy dependence of the capture cross sections. There appears to be an important "semidirect" component to the ( $p$ , $γ$ ) reaction leading to high-lying states in ${}^{12}C$ . We have also applied the same theory to calculate ${}^{12}C$ ( $γ$ , $p_{0}$ ) ${}^{11}B$ and ${}^{12}C$ ( $γ$ , $n_{0}$ ) ${}^{11}C$ transitions which have been previously measured.

NUCLEAR REACTIONS ( $p$ , $γ$ ) and ( $γ$ , $p$ ) reactions at medium energies; direct capture; states of high excitation energy in ${}^{12}C$ ; photodisintegration of ${}^{12}C$ .

Unitary pole approximations and expansions in few-body systems

A. Casel, H. Haberzettl, and W. Sandhas

Phys. Rev. C 25, 1738 (1982) - Published 1 April, 1982

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The unitary pole approximations or expansions of the two-body subsystem operators are well known, and particularly efficient and practical, methods to reduce the three-body problem to an effective two-body theory. In the present investigation we develop generalizations of these approximation techniques to the subsystem amplitudes of problems with higher particle numbers. They are based on the expansion of effective potentials which, in contrast to the genuine two-body interactions, are now energy dependent. Despite this feature our generalizations require only energy independent form factors, thus preserving one of the essential advantages of the genuine two-body approach. The application of these techniques to the four-body case is discussed in detail.

NUCLEAR REACTIONS Generalizations of unitary pole approximation and expansion. Application to four-body problem.

${}^{30}{Si}$ ( $p$ , $α$ ) ${}^{27}{Al}$ reaction from $E_{p} = 4.90 - 6.08$ MeV

J. S. Chang, V. K. C. Cheng, H. H. Lin, and C. C. Hsu

Phys. Rev. C 25, 1751 (1982) - Published 1 April, 1982

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Excitation energies and strengths of sixty-eight resonances in the compound nucleus ${}^{31}P$ formed by the reaction ${}^{30}{Si}$ ( $p$ , $α$ ) ${}^{27}{Al}$ were observed in the energy range $E_{p} = 4.90 - 6.08$ MeV. The natural widths of eighteen resonances are reported. The observed level density has been found in good agreement with a semiempirical theory. Angular distributions of ground-state alpha particles, measured at nine resonances, suggested spin and parity for eight levels and level-interference effect for one level.

NUCLEAR REACTIONS ${}^{30}{Si}$ ( $p$ , $α$ ), $E = 4.90 - 6.08$ MeV; measured $σ (E; E_{α}, θ)$ , ${}^{31}P$ ; deduced levels, $J$ , $π$ , orbital momentum mixing ratios; enriched target.

Spectroscopy of ${}^{16}F$ from the ${}^{16}O$ ( $p$ , $n$ ) ${}^{16}F$ reaction at 99 and 135 MeV

A. Fazely, B. D. Anderson, M. Ahmad, A. R. Baldwin, A. M. Kalenda, R. J. McCarthy, J. W. Watson, R. Madey, W. Bertozzi, T. N. Buti, J. M. Finn, M. A. Kovash, B. Pugh, and C. C. Foster

Phys. Rev. C 25, 1760 (1982) - Published 1 April, 1982

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We measured neutron energy spectra and extracted angular distributions for eleven separate transitions for the ${}^{16}O$ ( $p$ , $n$ ) ${}^{16}F$ reaction at 99.1 and 135.2 MeV. Several new spin and parity assignments are obtained for states in ${}^{16}F$ by comparison of the excitation energy spectra with known analog states in ${}^{16}O$ and with a shell-model prediction and by analysis of the neutron angular distributions. The most strongly-excited states are two $2^{-}$ states at $E_{x} = 0.40 \pm 0.05 and 7.6 \pm 0.1$ MeV, a $4^{-}$ state at 6.37±0.05 MeV, and two broad $1^{-}$ states at 9.4±0.1 and 11.5±0.1 MeV. These states are analogs of known $2^{-}$ ( $M 2$ ) states, a $4^{-}$ "stretched" state, and $1^{-}$ ( $E 1$ ) strength, respectively, in ${}^{16}O$ . Three weakly excited $1^{+}$ states are observed at $E_{x} = 3.75 \pm 0.05, 4.65 \pm 0.05, and 6.23 \pm 0.05$ MeV. These states are analogs of known $1^{+}$ ( $M 1$ ) states in ${}^{16}O$ and directly indicate correlations in the ground state of ${}^{16}O$ . A weakly excited $4^{-}$ state is seen at 5.93±0.05 MeV in good agreement with a $4^{-}$ state observed in ${}^{16}O$ ( $e$ , $e^{'}$ ) measurements. All of the most strongly excited states align (to within ±200 keV) with known $T = 1$ analog states in ${}^{16}O$ for a common net displacement energy of 12.6 MeV. The ( $p$ , $n$ ) reaction at medium energies is shown to be an important spectroscopic tool.

NUCLEAR REACTIONS ${}^{16}O$ ( $p$ , $n$ ) ${}^{16}F$ , $E = 99.1 and 135.2$ MeV; measured neutron spectra in ∼3° steps between 0° and 69°; extracted $σ (θ)$ for eleven separate transitions to discrete states in ${}^{16}F$ . Compared excitation energies with analog states in ${}^{16}O$ and with a shell-model prediction. Deduced several new $J^{π}$ assignments.

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Recent Issues

Some properties of projected three-body theories of deuteron-nucleus collisions

Determination of the $NN$ cross section in nuclei from inclusive ( $π$ , $π^{'}$ ) and coincidence ( $π$ , $π N$ ) reactions

Particle-hole ambiguity in the parameters of the microscopic interacting boson model

Simple formula for the ground band spectrum of even-mass rotational nuclei

Pion charge-exchange reaction and transition densities to isobaric analog states

Intermediate structure of the ${}^{12}C$ + ${}^{12}C$ system

Mass of ${}^{197}{Hg}$

Erratum: Fusion behavior in time-dependent Hartree-Fock calculations of ${}^{86}{Kr}$ + ${}^{139}{La}$ and ${}^{84}{Kr}$ + ${}^{209}{Bi}$ collisions

Erratum: ${}^{92, 94, 97, 98}{Mo}$ ( $t$ , $p$ ) reactions at $E_{t} = 17$ MeV

Erratum: Proton hole states in neutron rich nuclei near $A = 100$

Erratum: Unusual phenomena in fireball

Erratum: Effect of center-of-mass correlations and intermediate states on $π$ - ${}^{3}{He}$ scattering

Spin-orbit deformations deduced from analyzing powers for inelastic neutron scattering from ${}^{54}{Fe}$ , ${}^{56}{Fe}$ , ${}^{58}{Ni}$ , ${}^{60}{Ni}$ , ${}^{120}{Sn}$ , and ${}^{208}{Pb}$

Microscopic determination of the interacting boson model parameters

Effects of averaging on energy dependence of backward-angle heavy-ion cross sections: Calculations of "de-averaged" excitation functions

Analyzing power for the ${}^{16}O$ ( $\vec{p}$ , $n$ ) ${}^{16}F$ ( $4^{-}$ ,6.37 MeV) reaction at 134 MeV

Direct-reaction model for ( $p$ , $γ$ ) reactions to highly excited states in ${}^{12}C$

Unitary pole approximations and expansions in few-body systems

${}^{30}{Si}$ ( $p$ , $α$ ) ${}^{27}{Al}$ reaction from $E_{p} = 4.90 - 6.08$ MeV

Spectroscopy of ${}^{16}F$ from the ${}^{16}O$ ( $p$ , $n$ ) ${}^{16}F$ reaction at 99 and 135 MeV

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