Recent Articles

Elastic scattering and fusion of ${}^{16}O$ $+^{59}$ Co at near barrier energies: A signature for long range fusion potentials

C. Tenreiro, P. R. S. Gomes, T. J. P. Penna, R. Liguori Neto, J. C. Acquadro, P. A. B. Freitas, and E. Crema

Phys. Rev. C 49, 1218 (1994) - Published 1 February, 1994

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Elastic scattering angular distributions were measured for the ${}^{16}O$ $+^{59}$ Co system, at energies close to the Coulomb barrier. Simultaneous analysis of elastic scattering and fusion cross sections were performed, based on the optical model. The part of the imaginary potential which accounts for the fusion was found to be of long range, with values of $r_{f}$ larger than 1.42 fm, leading to the interpretation that fusion is decided at large separations, beyond the Coulomb barrier.

Decay of ${}^{98}{Rh}$

V. Banerjee, A. Banerjee, G. S. N. Murthy, R. P. Sharma, S. K. Pardha Saradhi, and A. Chakrabarti

Phys. Rev. C 49, 1221 (1994) - Published 1 February, 1994

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The decay of ${}^{98}{Rh}$ has been studied using γ and β spectroscopy techniques. The ${}^{96}{Ru}$ (α,pn) reaction was used to produce ${}^{98}{Rh}$ and the activities were transported to a low background counting station using a He-jet system. The β end point energy has been determined from the decay of ${}^{98 g}{Rh}$ to ${}^{98}{Ru}$ . The end-point energy determined in this study differs considerably from an earlier study using similar technique but agrees well with that of an earlier (p,n) reaction study. The present study has also resulted in a modified decay scheme (partial) for the decay of ${}^{98}{Rh}$ .

Correlation between ε/Δ and the P factor

B. D. Foy, R. F. Casten, N. V. Zamfir, and D. S. Brenner

Phys. Rev. C 49, 1224 (1994) - Published 1 February, 1994

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Critical role of ${}^{122, 123, 124}{Te}$ in s-process nucleosynthesis

J. R. de Laeter, C. L. Smith, and K. J. R. Rosman

Phys. Rev. C 49, 1227 (1994) - Published 1 February, 1994

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The s-only isotopes of tellurium ${}^{122, 123, 124}{Te}$ provide a unique opportunity to test s-process systematics. The neutron capture cross section ratios σ(Te)/σ(Au) at astrophysical energies have recently been determined with an uncertainty of approximately 1%. This provides the possibility of deriving limits for p-process contributions to these s-only isotopes. Unfortunately the absolute abundances of the tellurium isotopes have not been measured, so that errors in the existing isotopic data need to be more realistically assessed. This constrains the estimates of the magnitude of the p-process contributions and hence an investigation of s-process branching in this mass region.

Erratum: Analysis of the reaction $π^{+} d \to pp$ to 500 MeV

Richard A. Arndt, Igor I. Strakovsky, Ron L. Workman, and David V. Bugg

Phys. Rev. C 49, 1229 (1994) - Published 1 February, 1994

Selected Abstracts from Physical Review D

Phys. Rev. C 49, 1230 (1994) - Published 1 February, 1994

Pion elastic scattering on ${}^{28}{Si}$ at $T_{π}$ =400 MeV

M. W. Rawool-Sullivan, C. L. Morris, J. M. O’Donnell, R. M. Whitton, B. K. Park, G. R. Burleson, D. L. Watson, J. Johnson, A. L. Williams, D. A. Smith, D. J. Ernst, and C. M. Chen

Phys. Rev. C 49, 627 (1994) - Published 1 February, 1994

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Experimental differential cross sections for $π^{+}$ and $π^{-}$ elastic scattering on ${}^{28}{Si}$ at an incident pion energy of 400 meV are reported. The data fall above the predictions of a calculation using a momentum-space first-order optical potential. The behavior is similar to earlier results for pion scattering at $T_{π}$ =672 meV and to $K^{+}$ nucleus scattering in this energy range, suggesting that there may be a common origin for the observed discrepancy that is not yet understood.

Spin correlation measurements for p→+p→ elastic scattering at 497.5 MeV

G. W. Hoffmann, M. L. Barlett, W. Kielhorn, G. Pauletta, M. Purcell, L. Ray, J. F. Amann, J. J. Jarmer, K. W. Jones, S. Penttilä, N. Tanaka, G. Burleson, J. Faucett, M. Gilani, G. Kyle, L. Stevens, A. M. Mack, D. Mihailidis, T. Averett, J. Comfort, J. Görgen, and J. Tinsley

Phys. Rev. C 49, 630 (1994) - Published 1 February, 1994

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The spin correlation parameter $A_{00 N N}$ for 497.5 MeV proton + proton elastic scattering was determined over the center-of-momentum scattering angle region 23.1°–64.9 °. The new $A_{00 N N}$ extend to more forward angles than existing $A_{00 N N}$ and have significantly smaller statistical errors (±0.01–0.04). The $A_{00 N N}$ are qualitatively described by recent phase shift analyses, but a quantitative shape and normalization discrepancy remains in the forward angle region. These new data provide important constraints for nucleon-nucleon spin-dependent amplitudes at forward angles which are used in theoretical models of nucleon-nucleus scattering.

NN correlations and relativistic Hartree-Fock in finite nuclei

R. Fritz and H. Müther

Phys. Rev. C 49, 633 (1994) - Published 1 February, 1994

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Two different approximation schemes for the self-consistent solution of the relativistic Brueckner-Hartree-Fock equation for finite nuclei are discussed using realistic one-boson-exchange potentials. In a first scheme, the effects of correlations are deduced from a study of nuclear matter and parametrized in terms of an effective σ, ω, and π exchange. Employing this effective interaction relativistic Hartree-Fock equations are solved for finite nuclei ${}^{16}O$ , ${}^{40}{Ca}$ , and ${}^{48}{Ca}$ . In the second approach the effect of correlations are treated in the Brueckner-Hartree-Fock approximation directly for the finite nuclei, but the modifications of the Dirac spinors in the medium are derived from nuclear matter assuming a local-density approximation. Both approaches yield rather similar results for binding energies and radii in fair agreement with experimental data. The importance of the density dependent correlation effects is demonstrated and different ingredients to the spin-orbit splitting in the shell model of the nucleus are discussed.

Spin-lattice relaxation of Ra in Tl and g factor of the ${}^{213}{Ra}^{m}$ , τ=2.1 ms isomer

G. Neyens, R. Nouwen, G. S’heeren, M. Van Den Bergh, and R. Coussement

Phys. Rev. C 49, 645 (1994) - Published 1 February, 1994

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The nuclear spin-lattice relaxation of Ra in Tl is found to be mainly due to the magnetic dipole interaction of the nuclear spins with the conduction electrons in the Tl metal. The influence of magnetic spin-lattice relaxation on an initially oriented system of nuclear spins has been calculated as a function of the lattice temperature. Measurements of the time-integrated anisotropy as a function of the temperature permit to extract the Korringa constant for ${}^{213}{Ra}^{m}$ Tl and ${}^{214}{Ra}^{m}$ Tl. The Korringa relation has been used to derive the Knight shift K(RaTl) and to obtain the g factor for the ${}^{213}{Ra}$ isomer.

Octupole deformation in ${}^{149, 151}{Sm}$ nuclei

Somapriya Basu, J. M. Chatterjee, D. Banik, R. K. Chattopadhyay, R. P. Sharma, and S. K. Pardha Saradhi

Phys. Rev. C 49, 650 (1994) - Published 1 February, 1994

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Parity doublet states and alternating parity bands in ${}^{149, 151}{Sm}$ nuclei observed in ${}^{148, 150}{Nd}$ (α,3nγ) reactions at $E_{α}$ =37 and 35 MeV are presented here. Nineteen new transitions in ${}^{149}{Sm}$ and sixteen in ${}^{151}{Sm}$ have been observed in singles and γ-γ-t-r.f. coincidence experiments. Four alternating parity bands in ${}^{149}{Sm}$ and two in ${}^{151}{Sm}$ characterized by simplex quantum numbers are reported. The observed level schemes are interpreted in terms of octupole deformation. The energy difference due to parity splitting, collective rotational parameters, quasiparticle Routhians, single particle angular momentum alignments of bands with simplex quantum number s=±i in ${}^{149}{Sm}$ and with s=-i in ${}^{151}{Sm}$ have been calculated from the experimental results. From the E1, E2 branching ratios, the electric dipole moments are deduced to be 〈 $D_{0}$ 〉=0.19±0.08 e fm for ${}^{149}{Sm}$ and 〈 $D_{0}$ 〉=0.36±0.11 e fm for ${}^{151}{Sm}$ . The parameter $C_{1}$ , a function of the symmetry energy coefficient, has been estimated for ${}^{149}{Sm}$ from the liquid drop model of Strutinsky for deformed nucleus, and has been found to be $C_{1}$ =0. $002003_{- 0.000159}^{+ 0.000087}$ fm.

High-spin studies of ${}^{219}{Ac}$

F. Cristancho, J. X. Saladin, M. P. Metlay, W. Nazarewicz, C. Baktash, M. Halbert, I-Y. Lee, D. F. Winchell, S. M. Fischer, and M. K. Kabadiyski

Phys. Rev. C 49, 663 (1994) - Published 1 February, 1994

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High-spin states up to a probable spin I=45/2 have been investigated in ${}^{219}{Ac}$ using the reaction ${}^{209}{Bi}$ $(^{13}$ C,3n). The alternating parity sequences already observed up to I=31/2 do not seem to develop further at higher spins. A new side band was observed as well as several E2/M1 transitions linking the states of positive parity. Multipolarities and mixing ratios were deduced from an analysis of DCO ratios. In addition mixing ratios were obtained independently from the branching ratios. This allows for determination of B(M1)/B(E2) ratios up to $I^{π}$ =29/ $2^{+}$ . The data are discussed in terms of a transition from the weak coupling scheme at low and medium spins to the particle-hole regime for I≳31/2.

Intermediate structure in the neutron-induced fission cross section of ${}^{236}U$

Winifred E. Parker, J. Eric Lynn, George L. Morgan, Paul W. Lisowski, Allan D. Carlson, and Nat W. Hill

Phys. Rev. C 49, 672 (1994) - Published 1 February, 1994

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Neutron-induced fission of ${}^{236}U$ has been measured at the Los Alamos Neutron Scattering Center with a white neutron source using a fast parallel plate ionization chamber at a flight path of ∼56 m. In the resonance and the intermediate resonance region, very little of the previously reported structure was detected. Only five resonance structures were observed. Additionally, the width of the 5.45 eV resonance is approximately 100 times smaller than previously reported. An explanation for the discrepancies between old data and data reported here is discussed. New fission widths for resonances from 5.45 eV to 10.4 keV are reported. The new data are in agreement with theoretical estimates.

Comparison of Gamow-Teller strength in ${}^{37}{Ar}$ and ${}^{37}K$ and ${}^{37}{Cl}$ neutrino cross sections

Maurice B. Aufderheide, Stewart D. Bloom, David A. Resler, and Charles D. Goodman

Phys. Rev. C 49, 678 (1994) - Published 1 February, 1994

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We compare the Gamow-Teller strength distributions for the A=37 system as measured by the ${}^{37}{Ca}$ $β^{+}$ decay experiment with ${}^{37}{Cl}$ (p,n) experiments, considering the effect of suppression of β-delayed protons from the 3.239-MeV state in ${}^{37}K$ . We determine a range of values for the suppression of proton emission from this state for which the two measurements of strength are consistent. Recent studies of this state support this suppression and the amount of suppression is within our allowed range. Using the experimentally determined value for the suppression we are able to determine neutrino cross sections on ${}^{37}{Cl}$ from ${}^{8}B$ solar neutrinos, supernova neutrinos, and $μ^{+}$ decay neutrinos. Our cross section for $μ^{+}$ decay neutrinos is found to be 20% larger than the estimates of Bahcall, because of high-lying strength only recently confirmed by the ${}^{37}{Ca}$ $β^{+}$ decay experiment.

Multichannel study on the fragmentation of the 1 $g_{9 / 2}$ isobaric analog resonance in ${}^{53}{Mn}$

J. Sziklai, J. A. Cameron, I. M. Szöghy, and T. Vass

Phys. Rev. C 49, 686 (1994) - Published 1 February, 1994

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Fragments of the 1 $g_{9 / 2}$ isobaric analog resonance in ${}^{53}{Mn}$ corresponding to the 3.715 MeV state ( $S_{n}$ =0.57) in ${}^{53}{Cr}$ were located using the ${}^{52}{Cr}$ (p, $p_{0}$ ), ${}^{52}{Cr}$ (p, $p_{1}$ ), ${}^{52}{Cr}$ (p, $p_{1}$ γ), ${}^{52}{Cr}$ (p, $p_{2}$ γ), and ${}^{52}{Cr}$ (p,γ $)^{53}$ Mn reactions. Differential cross sections were measured in the 4.06–4.28 MeV, and the γ-excitation curves in the 4.04–4.35 MeV proton energy region. Spins, parities, and partial widths were determined with the aid of R-matrix analysis for all resonances observed in the region. The spins of the 1 $g_{9 / 2}$ resonance fragments were found independently from (p, $p_{1}$ γ), (p, $p_{2}$ γ), and (p,γ) angular distribution measurements and their analyses. Nineteen fragments were identified and their γ-branching ratios to low lying levels of ${}^{53}{Mn}$ were also deduced. Partial widths for each fragment in all four channels were derived. Channel-channel correlations were calculated. Fine structure analyses were carried out in all open channels. Inelastic spectroscopic factors and Coulomb displacement energy for the 1 $g_{9 / 2}$ state were also derived.

Nuclear g-factor measurement for the 21/ $2^{+}$ isomeric state in ${}^{89}{Nb}$

V. V. Krishnamurthy, S. N. Mishra, R. G. Pillay, S. H. Devare, H. G. Devare, and J. A. Sheikh

Phys. Rev. C 49, 705 (1994) - Published 1 February, 1994

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The nuclear g factor of the 14 ns 21/ $2^{+}$ isomeric state in ${}^{89}{Nb}$ has been measured using time differential perturbed γ-ray angular distribution (TDPAD) method following pulsed heavy-ion reaction and recoil implantation. From the observed spin precession frequency $ω_{L}$ in ferromagnetic Ni host, we obtain the g factor g(21/ $2^{+}$ )=0.324(7). The measured value is in good agreement with our shell model analysis carried out using the effective g factors for proton particles and neutron holes in the $g_{9 / 2}$ orbitals.

Spatial orientation of nuclei: Mass deformation in 165-holmium

J. E. Koster, C. R. Gould, D. G. Haase, and N. R. Roberson

Phys. Rev. C 49, 710 (1994) - Published 1 February, 1994

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Measurements of neutron transmssion through a rotating, cryogenically aligned holmium target are reported. From the variation in the transmission yield as a function of alignment angle we obtain holmium deformation cross sections of -548±42, -354±17, -283±23, and 248±23 mb at neutron energies 1.5, 1.8, 1.9, and 3.9 MeV, respectively. Coupled channels calculations using deformed optical model parameters give a quadrupole mass deformation length $β_{2}$ $r_{0}$ =0.38±0.03, consistent with the literature. In contrast to a recent result from analysis of pion single-charge-exchange scattering, the data imply similar deformation lengths for the proton and neutron distributions in holmium.

Superdeformed bands in ${}^{191}{Tl}$

S. Pilotte, C.-H. Yu, H. Q. Jin, J. M. Lewis, L. L. Riedinger, Y. Liang, R. V. F. Janssens, M. P. Carpenter, T. L. Khoo, T. Lauritsen, F. Soramel, I. G. Bearden, C. Baktash, J. D. Garrett, N. R. Johnson, I. Y. Lee, and F. K. McGowan

Phys. Rev. C 49, 718 (1994) - Published 1 February, 1994

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High spin states in the ${}^{191}{Tl}$ nucleus have been populated via the ${}^{159}{Tb}$ $(^{36}$ S,4n) reaction at 165 MeV. Two weakly populated rotational bands have been observed with properties (energy spacings and dynamic moments of inertia) very similar to those of other superdeformed bands in the A∼190 region. The two bands can be interpreted as signature partners which exhibit some signature splitting for rotational frequencies ħω≥0.2 MeV. They are interpreted within the framework of cranked Woods-Saxon calculations as being based on the proton $i_{13 / 2}$ (Ω=5/2) intruder orbital, in agreement with pairs of superdeformed bands seen in neighboring odd Tl nuclei.

Spectroscopy of the isotones ${}^{215}{Rn}$ and ${}^{217}{Ra}$

R. K. Sheline, C. F. Liang, P. Paris, A. Gizon, and V. Barci

Phys. Rev. C 49, 725 (1994) - Published 1 February, 1994

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The level structure of ${}^{215}{Rn}$ has been studied by observing the alpha decay of ${}^{219}{Ra}$ ( $t_{1 / 2}$ =10 ms) in secular equilibrium with ${}^{232}{Th}$ ( $t_{1 / 2}$ =0.66 s) produced by the reaction ${}^{208}{Pb}$ $(^{18}$ O,3n). Guidance in the interpretation of the five levels is available from the more comprehensive level structure of the isotone ${}^{217}{Ra}$ . Both of these level structures are interpreted in terms of the shell model and the reflection asymmetric model.

Transition strengths and multiple band structure in ${}^{82}{Sr}$

S. L. Tabor, J. Döring, J. W. Holcomb, G. D. Johns, T. D. Johnson, T. J. Petters, M. A. Riley, and P. C. Womble

Phys. Rev. C 49, 730 (1994) - Published 1 February, 1994

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High-spin states in ${}^{82}{Sr}$ were studied using the ${}^{56}{Fe}$ $(^{29}$ Si,2pn) reaction at 95 MeV with a thick 78 mg/ ${cm}^{2}$ natural Fe (92% ${}^{56}{Fe}$ ) target. Prompt γ-γ coincidences were measured using three Compton-suppressed Ge detectors at 90° relative to the beam and two at 30°. Directional correlation of oriented nuclei ratios were determined from the 30°– 90° coincidences to assist in assigning spin changes. Nine new states were found, along with 38 new transitions. The Doppler-shift attenuation method was used to determine the mean lifetimes of 22 states in ${}^{82}{Sr}$ . The continuum side feeding times into 10 states were determined by comparing the decay line shapes in coincidence with transitions above and below the state under study. The average transition quadrupole moment of 2.8(2) e b in the ground state band of ${}^{82}{Sr}$ would correspond to a relatively large axial quadrupole deformation of $β_{2}$ =0.33, in agreement with theoretical predictions. The excited $2^{+}$ band has a higher moment of inertia but a lower transition quadrupole moment of 2.4(2) e b. In the negative-parity bands the quadrupole moment falls from about 3 to 2 e b with increasing spin.

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Elastic scattering and fusion of ${}^{16}O$ $+^{59}$ Co at near barrier energies: A signature for long range fusion potentials

Decay of ${}^{98}{Rh}$

Correlation between ε/Δ and the P factor

Critical role of ${}^{122, 123, 124}{Te}$ in s-process nucleosynthesis

Erratum: Analysis of the reaction $π^{+} d \to pp$ to 500 MeV

Selected Abstracts from Physical Review D

Pion elastic scattering on ${}^{28}{Si}$ at $T_{π}$ =400 MeV

Spin correlation measurements for p→+p→ elastic scattering at 497.5 MeV

NN correlations and relativistic Hartree-Fock in finite nuclei

Spin-lattice relaxation of Ra in Tl and g factor of the ${}^{213}{Ra}^{m}$ , τ=2.1 ms isomer

Octupole deformation in ${}^{149, 151}{Sm}$ nuclei

High-spin studies of ${}^{219}{Ac}$

Intermediate structure in the neutron-induced fission cross section of ${}^{236}U$

Comparison of Gamow-Teller strength in ${}^{37}{Ar}$ and ${}^{37}K$ and ${}^{37}{Cl}$ neutrino cross sections

Multichannel study on the fragmentation of the 1 $g_{9 / 2}$ isobaric analog resonance in ${}^{53}{Mn}$

Nuclear g-factor measurement for the 21/ $2^{+}$ isomeric state in ${}^{89}{Nb}$

Spatial orientation of nuclei: Mass deformation in 165-holmium

Superdeformed bands in ${}^{191}{Tl}$

Spectroscopy of the isotones ${}^{215}{Rn}$ and ${}^{217}{Ra}$

Transition strengths and multiple band structure in ${}^{82}{Sr}$

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