Recent Articles

Absence of closed shell effect in the fusion reaction ${}^{40}{Ca}$ + ${}^{48}{Ca}$ at 330 MeV

J. Barreto, L. Tassan-Got, C. Stephan, J. P. Garron, and M. Langevin

Phys. Rev. C 25, 1641 (1982) - Published 1 March, 1982

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A direct comparison of the complete fusion cross section of the reaction ${}^{40}{Ar}$ + ${}^{48}{Ti}$ with the double magic ${}^{40}{Ca}$ + ${}^{48}{Ca}$ fusion cross section has been done with 330 MeV projectile energy. The compound nucleus ${}^{88}{Zr}$ was formed with nearly the same excitation energy and identical angular momentum population in both reactions. A $Δ E - E$ telescope placed in the focal plane of a spectrometer, associated with a time of flight allowed a complete identification of the reaction products. Evaporation residues were also detected inside the scattering chamber with a $Δ E - E$ silicon telescope. From both measurements, there was no evidence for a closed shell effect in the complete fusion reaction.

NUCLEAR REACTIONS ${}^{40}{Ca}$ + ${}^{48}{Ca}$ , ${}^{40}{Ar}$ + ${}^{48}{Ti}$ , $E_{lab} = 330$ MeV, measured fusion cross sections.

${}^{3}H$ ( $p$ , $γ$ ) ${}^{4}{He}$ reaction below $E_{p} = 30$ MeV

R. C. McBroom, H. R. Weller, N. R. Roberson, and D. R. Tilley

Phys. Rev. C 25, 1644 (1982) - Published 1 March, 1982

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We have measured the cross section for the ${}^{3}H$ ( $p$ , $γ$ ) ${}^{4}{He}$ reaction for incident proton energies from 8-30 MeV. The absolute 90° differential cross section below $E_{p} = 18$ MeV is in reasonable agreement with previous results. Angular distributions were measured at eight energies between $E_{p} = 13 and 30$ MeV. The coefficients which result from fitting these data to an expansion in Legendre polynomials are reported.

NUCLEAR REACTIONS ${}^{3}H$ ( $p$ , $γ$ ), measured $σ (E, θ)$ from $E_{p} = 8 - 30$ MeV. Obtained Legendre polynomial coefficients.

Effect of reflections in pion-deuteron scattering

Humberto Garcilazo

Phys. Rev. C 25, 1649 (1982) - Published 1 March, 1982

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We compare the solutions of the Faddeev equations for pion-deuteron scattering, with and without the reflection terms in which the pion is allowed to scatter back and forth between the two nucleons. We show that in the resonance region, the effect of these terms in the differential cross section is less than 20%. We point out that the Faddeev equations without reflections, reduce to a Lippmann-Schwinger equation with a pion-deuteron effective potential. We also point out that the pole approximation to the nucleon-nucleon $T$ matrix is not a very good approximation.

NUCLEAR REACTIONS $π - d$ scattering, reflection terms; calculated $\frac{d σ}{d Ω}$ , $E = 142, 181, and 228$ MeV.

Leading particle effect on antiproton annihilation in neon

Chikai Ishii

Phys. Rev. C 25, 1652 (1982) - Published 1 March, 1982

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Semiclassical transport theory is applied to the pion emission from antiproton annihilation in Ne. In the annihilation of a moving antiproton in nuclei, we find that the leading particle effect is apparent.

NUCLEAR REACTIONS Low energy $\bar{p}$ -Ne annihilation; pion transport theory; leading particle effect.

Graphical multistep shell-model calculation of the even tin and lead ground states

C. Pomar and R. J. Liotta

Phys. Rev. C 25, 1656 (1982) - Published 1 March, 1982

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The ground-state energies and wave functions of tin and lead even isotopes are calculated within a multistep shell-model method and good agreement with experimental data is obtained. To carry out this calculation a general graphical procedure is introduced.

NUCLEAR STRUCTURE Calculated ground states of tin and lead isotopes.

Semiclassical interpretation of meson exchange currents

J. L. Friar, E. L. Tomusiak, and J. Dubach

Phys. Rev. C 25, 1659 (1982) - Published 1 March, 1982

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$g$ factors at high spins

A. Ansari and S. C. K. Nair

Phys. Rev. C 25, 1664 (1982) - Published 1 March, 1982

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Rotational $g$ factors as a function of angular momentum for two backbending nuclei ${}^{158}{Er}$ and ${}^{160}{Yb}$ and for a well deformed nonbackbender ${}^{172}{Yb}$ are calculated in the cranked Hartree-Fock-Bogoliubov method. For the backbenders the $g$ factor decreases sharply with angular momentum and reaches a minimum around $J = 12$ . For ${}^{172}{Yb}$ the decrease is weaker.

NUCLEAR STRUCTURE $g$ factors of high spin states; backbending region.

Occupancy and structural changes in upper $f - p$ shell nuclei

V. K. B. Kota, S. P. Pandya, and V. Potbhare

Phys. Rev. C 25, 1667 (1982) - Published 1 March, 1982

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We use spectral distribution methods to calculate proton occupancies in ground states of nuclei in the range $A = 60 - 80$ , and show that these results indicate structural changes around $N = 40 - 44$ .

NUCLEAR STRUCTURE Spectral distribution calculations of ground state proton occupation numbers in Zn, Ge, Se, and Kr nuclei.

Neutrino reactions in ${}^{12}C$

S. L. Mintz

Phys. Rev. C 25, 1671 (1982) - Published 1 March, 1982

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Total and differential cross sections for the reaction $ν_{μ} + {}^{12}C \to μ^{-} + {}^{12}N$ and total cross sections for the reactions $ν_{e} + {}^{12}C \to e^{-} + {}^{12}N$ , $ν + {}^{12}C \to {}^{12}C^{*} + ν$ and the corresponding antineutrino reactions are calculated for neutrino energy from threshold to the 250 MeV range. The effect of the pseudotensor form factor on these results is examined.

NUCLEAR REACTIONS Total and differential cross sections for ${}^{12}C$ ( $ν_{μ}$ , $μ^{-}$ ) ${}^{12}N$ and total cross sections for ${}^{12}C$ ( $ν_{e}$ , $e^{-}$ ) ${}^{12}N$ , ${}^{12}C$ ( ${\bar{ν}}_{e}$ , $e^{+}$ ) ${}^{12}B$ , ${}^{12}C$ ( $ν$ , $ν$ ) ${}^{12}C$ *, ${}^{12}C$ ( $\bar{ν}$ , $\bar{ν}$ ) ${}^{12}C$ * are obtained.

Elastic neutron-deuteron doublet scattering near the deuteron breakup threshold

V. S. Bhasin and V. K. Gupta

Phys. Rev. C 25, 1675 (1982) - Published 1 March, 1982

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The anomalous behavior, as suggested by Efimov, in the doublet $n - d$ scattering near the deuteron breakup threshold is investigated by computing the coupled integral equation using $s$ -wave separable potentials.

NUCLEAR REACTIONS Elastic scattering, neutron-deuteron amplitude, separable potentials, Efimov effect.

Comment on "Nucleus-nucleus total reaction cross sections"

L. W. Townsend and J. W. Wilson

Phys. Rev. C 25, 1679 (1982) - Published 1 March, 1982

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In a recent article by DeVries and Peng, it was suggested that the concept of a geometric reaction cross section was not meaningful since $σ_{R}$ exceeded the geometric values for heavy nuclear charge distributions, in place of the required nuclear single-particle distributions, in the calculations for $σ_{R}$ . Hence, the applicability of geometric limits for $σ_{R}$ remains undetermined.

NUCLEAR REACTIONS Total reaction cross section predictions for ${}^{40}{Ca}$ + ${}^{40}{Ca}$ , ${}^{40}{Ca}$ + ${}^{208}{Pb}$ , ${}^{208}{Pb}$ + ${}^{208}{Pb}$ , and the validity of geometric cross sections. Energy range $0.1 < E_{lab} < 23$ GeV/nucleon.

Analyzing powers for neutron elastic scattering at forward angles

C. E. Floyd, P. P. Guss, K. Murphy, C. R. Howell, R. C. Byrd, G. Tungate, S. A. Wender, R. L. Walter, and T. B. Clegg

Phys. Rev. C 25, 1682 (1982) - Published 1 March, 1982

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Accurate neutron analyzing powers have been obtained using a new pulsed polarized neutron facility. Data are presented for elastic scattering of 14-MeV neutrons from ${}^{40}{Ca}$ , ${}^{54}{Fe}$ , ${}^{65}{Cu}$ , ${}^{120}{Sn}$ , and ${}^{208}{Pb}$ between 18° and 36°. Our data exhibit no evidence for the anomalously large values which were reported previously at 20°.

NUCLEAR REACTIONS ${}^{40}{Ca}$ , ${}^{54}{Fe}$ , ${}^{65}{Cu}$ , ${}^{120}{Sn}$ , ${}^{208}{Pb}$ ( $\vec{n}$ , $n$ ), $E = 14.0$ MeV; measured $A_{y} (θ)$ , $θ = 18 ° - 36 °$ ; compared to previous results.

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Time reversal and charge symmetry studies in single nucleon transfer reactions in the $A = 5$ system

A. L. Sagle, F. P. Brady, J. L. Romero, B. E. Bonner, N. S. P. King, M. W. McNaughton, and H. E. Conzett

Phys. Rev. C 25, 1685(R) (1982) - Published 1 March, 1982

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Time-reversal invariance and charge symmetry have been studied in polarization measurements of single-nucleon transfer reactions in the mass five system. First, we experimentally established the equality of the proton analyzing power, $A$ , for ${}^{4}{He}$ ( $\vec{p}$ , $d$ ) ${}^{3}{He}$ at 32 MeV and the polarization, $P$ , of the inverse reaction, thereby checking time-reversal invariance. Then in a double scattering experiment using the reactions ${}^{3}H$ ( $d$ , $\vec{n}$ ) ${}^{4}{He}$ and ${}^{4}{He}$ ( $\vec{n}$ , $d$ ) ${}^{3}H$ at $θ_{c . m .} = 38.6 °$ and assuming $P = A$ (from time-reversal invariance) we obtained a polarization of 0.480 ± 0.016 for the 50 MeV neutrons. When this value is used, good agreement is found between the analyzing power distributions of ${}^{4}{He}$ ( $\vec{n}$ , $d$ ) ${}^{3}H$ and ${}^{4}{He}$ ( $\vec{p}$ , $d$ ) ${}^{3}{He}$ at 50 MeV, which is consistent with charge symmetry.

NUCLEAR REACTIONS ${}^{4}{He}$ ( $\vec{p}$ , $d$ ) ${}^{3}{He}$ , $E_{p} = 32 and 50$ MeV; ${}^{4}{He}$ ( $\vec{n}$ , $d$ ) ${}^{3}H$ , $E_{n} = 50$ MeV. Measured $A_{ν} (θ)$ , $θ = 25 ° - 150 °$ c.m. Inferred neutron polarization for reaction ${}^{3}H$ ( $d$ , $\vec{n}$ ) ${}^{4}{He}$ at $E_{d} = 37.1$ MeV, $θ = 38.6 °$ c.m.

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Concentration of $E 2$ strength near the fission barrier of ${}^{232}{Th}$

J. D. T. Arruda-Neto, M. F. B. M. Vannucci, S. B. Herdade, A. Vannucci, and I. C. Nascimento

Phys. Rev. C 25, 1689(R) (1982) - Published 1 March, 1982

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The electrofission angular distribution of ${}^{232}{Th}$ , in the energy interval 5.5-7 MeV, was measured. The analysis of the $E 2$ coefficient of the angular distribution revealed that a substantial amount of $E 2$ fission strength is concentrated near the fission barrier, corresponding to (8±2)% of one energy-weighted sum-rule unity.

NUCLEAR REACTIONS ${}^{232}{Th}$ ( $e$ , $f$ ), $E = 5.5 - 7$ MeV, with electrons; measured fission-fragment angular distributions; deduced $E 2$ fission strength. Natural target.

RAPID COMMUNICATION

Alpha-particle emission from the deep-inelastic reaction 1354 MeV ${}^{165}{Ho}$ + ${}^{181}{Ta}$

L. G. Sobotka, R. J. McDonald, G. J. Wozniak, D. J. Morrissey, A. J. Pacheco, and L. G. Moretto

Phys. Rev. C 25, 1693(R) (1982) - Published 1 March, 1982

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The in-plane correlation between projectilelike fragments and $α$ particles has been studied over a broad range of angles for the system 1354 MeV ${}^{165}{Ho}$ + ${}^{181}{Ta}$ . These data unambiguously indicate that the dominant sources of $α$ particles are the fully accelerated fragments.

NUCLEAR REACTIONS ${}^{181}{Ta}$ ( ${}^{165}{Ho}$ , $x$ ), $E = 1354$ MeV, measured $σ (E_{α}, θ)$ .

RAPID COMMUNICATION

Difference in anomalous $0_{g}^{+} \to 0_{g}^{+}$ ( $p$ , $t$ ) analyzing powers for the isotones and partial cross sections for spin up and down

Y. Aoki, H. Iida, S. Kunori, K. Nagano, Y. Toba, and K. Yagi

Phys. Rev. C 25, 1696(R) (1982) - Published 1 March, 1982

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A drastic difference of anomalous $0_{g}^{+} \to 0_{g}^{+}$ ( $p$ , $t$ ) analyzing powers on ${}^{92}{Zr}$ and ${}^{94}{Mo}$ is explained in terms of partial cross sections $σ_{m_{p} m_{t}}$ with $m_{p} = m_{t} = \pm \frac{1}{2}$ . It results from $σ_{- \frac{1}{2} - \frac{1}{2}} \approx 0$ only for ${}^{94}{Mo}$ due to a completely destructive interference between the one-step and the two-step ( $p$ , $d$ ) ( $d$ , $t$ ) sequential process.

NUCLEAR REACTIONS Vector analyzing power $A_{y} (θ)$ and partial cross sections $σ_{+ +} (θ)$ and $σ_{- -} (θ)$ for g.s. ( $p$ , $t$ ) on ${}^{92}{Zr}$ and ${}^{94}{Mo}$ , $E_{p} = 22$ MeV. First- and second-order DWBA.

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In-beam spectroscopy of neutron-rich nuclei: New application of massive-transfer reactions

D. R. Haenni, T. T. Sugihara, R. P. Schmitt, G. Mouchaty, and U. Garg

Phys. Rev. C 25, 1699(R) (1982) - Published 1 March, 1982

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In-beam $γ$ -ray spectroscopic studies have been performed using massive-transfer reactions induced by ${}^{7}{Li}$ ions on ${}^{100}{Mo}$ and ${}^{154}{Sm}$ targets to assess the characteristics of the technique and to obtain new spectroscopic information for ${}^{104}{Ru}$ and ${}^{156}{Gd}$ . This method opens new regions of neutron-rich nuclei for spectroscopic studies and provides a favorable population of high-spin states. Massive-transfer reactions are found also to provide an excellent filter for isolating events leading to specific reaction products.

NUCLEAR REACTIONS ${}^{100}{Mo}$ , ${}^{154}{Sm}$ ( ${}^{7}{Li}$ , $Xxn γ$ ), $X = p, d, t, α$ , $E = 48$ MeV. Measured $γ (E_{X})$ , $γ γ (E_{X})$ . ${}^{104}{Ru}$ , ${}^{156}{Gd}$ deduced levels.

RAPID COMMUNICATION

Anomalously low cross section in ${}^{13}C$ ( $γ$ , $π^{-}$ ) ${}^{13}N_{g . s .}$

John J. LeRose, K. Min, D. Rowley, B. O. Sapp, P. Stoler, E. J. Winhold, P. F. Yergin, A. M. Bernstein, K. I. Blomqvist, S. Dytman, G. Franklin, and M. Pauli

Phys. Rev. C 25, 1702(R) (1982) - Published 1 March, 1982

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Differential cross sections for the reaction ${}^{13}C$ ( $γ$ , $π^{-}$ ) ${}^{13}N_{g . s .}$ were measured at 90° (lab) for three pion energies: 17, 29, and 42 MeV. The experimental cross sections are anomalously low compared with distorted wave impulse approximation calculations and contrary to the predicted enhancement due to pion condensation precursor effect.

NUCLEAR REACTIONS ${}^{13}C$ ( $γ$ , $π^{-}$ ) ${}^{13}N_{g . s .}$ ; $E_{π} = 17, 29, and 42$ MeV; measured $σ (E_{π}, θ = 90 °)$ ; compared with DWIA calculations.

RAPID COMMUNICATION

Antisymmetrization of the ${}^{6}{Li}$ wave function and direct interaction for ( ${}^{6}{Li}$ , $d$ ) reactions

P. Singh and Arun K. Jain

Phys. Rev. C 25, 1705(R) (1982) - Published 1 March, 1982

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The product of the ${}^{6}{Li}$ wave function and direct interaction which appears in the finite-range—distorted-wave Bron approximation analyses of ( ${}^{6}{Li}$ , $d$ ) and ( $d$ , ${}^{6}{Li}$ ) reactions has been evaluated using an antisymmetrized cluster model ${}^{6}{Li}$ wave function and a free $N - N$ interaction. The exchange terms have been found to be more important than the direct term itself. This derived quantity has been shown to be very different from what is normally used in the analyses of ( ${}^{6}{Li}$ , $d$ ) and ( $d$ , ${}^{6}{Li}$ ) reactions.

NUCLEAR REACTIONS ( ${}^{6}{Li}$ , $d$ ), calculated antisymmetrized ${}^{6}{Li}$ wave function times direct interaction.

Snowball model for light fragment production

David H. Boal and Mehr Soroushian

Phys. Rev. C 25, 1003 (1982) - Published 1 February, 1982

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The snowball model for proton and electron induced light fragment production is investigated in some detail. The model involves a single scattering of the projectile, and multiple scatterings of the struck nucleon to form the observed fragment. The parameters of the model are examined and compared with qualitative estimates obtained by different methods. Predictions are made for electron induced fragment production.

NUCLEAR REACTIONS Snowball model for inclusive production of light fragments; electron and proton induced reactions.

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Absence of closed shell effect in the fusion reaction ${}^{40}{Ca}$ + ${}^{48}{Ca}$ at 330 MeV

${}^{3}H$ ( $p$ , $γ$ ) ${}^{4}{He}$ reaction below $E_{p} = 30$ MeV

Effect of reflections in pion-deuteron scattering

Leading particle effect on antiproton annihilation in neon

Graphical multistep shell-model calculation of the even tin and lead ground states

Semiclassical interpretation of meson exchange currents

$g$ factors at high spins

Occupancy and structural changes in upper $f - p$ shell nuclei

Neutrino reactions in ${}^{12}C$

Elastic neutron-deuteron doublet scattering near the deuteron breakup threshold

Comment on "Nucleus-nucleus total reaction cross sections"

Analyzing powers for neutron elastic scattering at forward angles

Time reversal and charge symmetry studies in single nucleon transfer reactions in the $A = 5$ system

Concentration of $E 2$ strength near the fission barrier of ${}^{232}{Th}$

Alpha-particle emission from the deep-inelastic reaction 1354 MeV ${}^{165}{Ho}$ + ${}^{181}{Ta}$

Difference in anomalous $0_{g}^{+} \to 0_{g}^{+}$ ( $p$ , $t$ ) analyzing powers for the isotones and partial cross sections for spin up and down

In-beam spectroscopy of neutron-rich nuclei: New application of massive-transfer reactions

Anomalously low cross section in ${}^{13}C$ ( $γ$ , $π^{-}$ ) ${}^{13}N_{g . s .}$

Antisymmetrization of the ${}^{6}{Li}$ wave function and direct interaction for ( ${}^{6}{Li}$ , $d$ ) reactions

Snowball model for light fragment production

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