Recent Articles

Solar neutrinos from the decay of ${}^{8}B$

John N. Bahcall and Barry R. Holstein

Phys. Rev. C 33, 2121 (1986) - Published 1 June, 1986

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The spectrum of neutrinos produced by the beta decay of ${}^{8}B$ in the sun is computed including forbidden corrections to the weak interactions. The total cross section for absorption by ${}^{37}{Cl}$ of ${}^{8}B$ neutrinos is (1.06±0.1)× $10^{- 42}$ ${cm}^{2}$ . The uncertainty is determined by calculating the cross section using different measured spectra for the alpha particles that result from the decay of ${}^{8}B$ to ${}^{8}{Be}$ and by varying the transition matrix elements consistent with the branching ratios measured using delayed protons emitted in the beta decay of ${}^{37}{Ca}$ .

Distortion in the β-decay spectrum for low electron kinetic energies

B. Eman and D. Tadić

Phys. Rev. C 33, 2128 (1986) - Published 1 June, 1986

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${}^{234}U$ excited states fed in the β decay of ${}^{234}{Pa}$

C. Ardisson, J. Dalmasso, and G. Ardisson

Phys. Rev. C 33, 2132 (1986) - Published 1 June, 1986

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The decay of radiochemically separated ${}^{234}{Pa}$ (UZ) sources has been reinvestigated by means of single and γ-γ coincidence spectrometry using planar and high efficiency coaxial HPGe detectors. Of the 330 γ rays observed in the 40–2100 keV energy range, of which 140 are new, more than 310 γ rays are accommodated in an improved ${}^{234}U$ level scheme, accounting for 98% of the ${}^{234}{Pa}$ β decay; of the 77 excited states observed here, 37 had not been previously found in this decay. Within the framework of the collective model of strongly deformed nuclei, couplings between the collective positive parity $K^{π}$ ${= 0}_{1}^{+}$ (g.s. band), $0_{2}^{+}$ , $2_{1}^{+}$ , $0_{3}^{+}$ , and $2_{2}^{+}$ bands are estimated from the perturbed transition probabilities and the distortions to the adiabatic energy systematics. The Coriolis interaction weakly coupling the $K^{π}$ ${= 0}^{-}$ , $1^{-}$ , and $2^{-}$ octupole bands was evaluated consistently by a fit to the experimental energy levels. Several new levels and a tentative $K^{π}$ ${= 3}^{+}$ band (at 1770 keV) are discussed in terms of Nilsson orbitals assignments.

Decay of 7.3-min ${}^{235}{Th}$ and 24.6-min ${}^{235}{Pa}$

S. Mirzadeh, Y. Y. Chu, S. Katcoff, and L. K. Peker

Phys. Rev. C 33, 2159 (1986) - Published 1 June, 1986

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Sources of ${}^{235}{Th}$ and ${}^{235}{Pa}$ were prepared by medium energy neutron and proton irradiations of uranium followed by radiochemical separations. Gamma-ray spectroscopy showed 13 new γ rays in the decay of ${}^{235}{Th}$ . Its half-life is 7.3±0.1 min, and that of ${}^{235}{Pa}$ is 24.6±0.2 min. A partial decay scheme is proposed for ${}^{235}{Th}$ , and a large anomalous retardation is reported in one branch of the ${}^{235}{Pa}$ $β^{-}$ decay.

Characterization of isomers in ${}^{158}{Ho}$

P. C. Sood, R. W. Hoff, and R. K. Sheline

Phys. Rev. C 33, 2163 (1986) - Published 1 June, 1986

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The experimentally known isomers of ${}^{158}{Ho}$ have been characterized by estimating the energies of two-quasiparticle excitations. Included in this modeling is the effect of a residual n-p interaction. A 21-min isomer is assigned the configuration $K^{π}$ ${= 9}^{+}$ { ${(7 / 2)}^{-}$ [523↑] ${}_{p {+ (11 / 2)}^{-} [505 ↑]_{n}}}$ and is predicted to lie 180 keV above the $5^{+}$ ground state. The antiparallel $K^{π}$ ${= 2}^{+}$ state of this configuration is assigned to an observed level at 316 keV. The 21-min isomer decays by an allowed unhindered transition to a 2528-keV level in ${}^{158}{Dy}$ for which we confirm the two-quasineutron configuration $K^{π}$ ${= 8}^{+}$ { ${(5 / 2)}^{-}$ [523↓] ${}_{n}$ ${+ (11 / 2)}^{-}$ [505↑ $]_{n}}$ . A 27-min $2^{-}$ isomer at 67.3 keV and a 29-ns $5^{-}$ isomer at 156.9 keV are assigned the configuration { ${(7 / 2)}^{+}$ [404↓ $]_{p}$ ∓ ${(3 / 2)}^{-}$ [521↑ $]_{n}}$ . A 1.85-ns $1^{-}$ isomer at 139.2 keV is assigned the configuration { ${(5 / 2)}^{+}$ [402↑ $]_{p}$ ${+ (3 / 2)}^{-}$ [521↑ $]_{n}}$ and the $K^{π}$ ${= 4}^{-}$ member of this Gallagher-Moszkowski pair is predicted to occur at 70 keV. Specific experiments are suggested to verify these predictions.

Half-life limit for ${}^{48}{Ca}$ (2 $β^{-}$ $)^{48}$ Ti( $0_{2}^{+}$ ,2997)

D. E. Alburger and J. B. Cumming

Phys. Rev. C 33, 2169 (1986) - Published 1 June, 1986

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Gamma-gamma coincidence data from a previous search for the decay sequence ${}^{48}{Ca}$ ( $β^{-}$ $)^{48}$ Sc( $β^{-}$ $)^{48}$ Ti, in which a sample containing 3.71 g of ${}^{48}{Ca}$ was counted for 206 days in a HPGe(well-type)-NaI(Tl) detector combination, were reanalyzed to place a half-life limit on ${}^{48}{Ca}$ (2 $β^{-}$ $)^{48}$ Ti( $0_{2}$ ${}^{+}$ , 2997). The signature for this decay would be the detection of 2014-983-keV γγ coincidences. An ${}^{88}Y$ source was used to establish the γγ coincidence efficiency. A lower limit (95% confidence) of $T_{1 / 2}$ >8× $10^{18}$ yr was obtained for the partial half-life for the 2 $β^{-}$ decay of ${}^{48}{Ca}$ to the 2997-keV $0_{2}^{+}$ level of ${}^{48}{Ti}$ .

Mechanism of pion double charge exchange at $T_{π}$ =292 MeV

H. T. Fortune and R. Gilman

Phys. Rev. C 33, 2171 (1986) - Published 1 June, 1986

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At 5° and 292 MeV, the A dependence of pion-induced double-charge-exchange cross sections on T=1 targets differs significantly from the $A^{- 10 / 3}$ behavior expected theoretically. The addition of a second process, whose cross section varies as $A^{- 4 / 3}$ , provides a good fit to the data. The resulting two-amplitude model predicts cross sections for heavier (T>1) nuclei that are in agreement with experiment.

K-shell ionization in the beta decay of ${}^{141}{Ce}$

H. J. Nagy and G. Schupp

Phys. Rev. C 33, 2174 (1986) - Published 1 June, 1986

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The total K-shell ionization probability accompanying the $β^{-}$ decay of ${}^{141}{Ce}$ to the 0.145-MeV level in ${}^{141}\Pr$ was determined to be (1.79±0.11)× $10^{- 4}$ from Pr Kα x rays in coincidence with the 0.145-MeV gamma ray. This result is in very good agreement with the theoretical calculations of Law and Suzuki.

Magnetic moment and lifetime of the 127 keV state in ${}^{101}{Ru}$

R. Schuhmann and C. Hohenemser

Phys. Rev. C 33, 2176 (1986) - Published 1 June, 1986

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Using ${BaF}_{2}$ scintillation counters and a source of ${}^{101}{Fe}$ we have determined the magnetic moment of the 127 keV first excited state of ${}^{101}{Ru}$ , using time differential perturbed angular correlations. Via the known hyperfine field of Ru in Fe we deduce g=-0.138(5) and g=-0.142(5) for annealed and quenched sources, respectively, and obtain a new, accurate value of the half-life, $T_{1 / 2}$ =0.655(4) nsec.

Spin-dipole isovector resonances in ${}^{12}C$ and ${}^{6}{Li}$ by positive photopion production

K. Shoda, M. Torikoshi, O. Sasaki, S. Tyama, T. Kobayashi, A. Kagaya, and H. Tsubota

Phys. Rev. C 33, 2179 (1986) - Published 1 June, 1986

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The energy and angular distributions of positive photopions emitted following the (e, $π^{+}$ ) reaction on ${}^{12}C$ and ${}^{6}{Li}$ has been studied for the spin-dipole isovector states in the highly excited residual nuclei. These states are found at ∼7 MeV in ${}^{12}B$ and 13.6, 17.7, and 24.0 MeV in ${}^{6}{He}$ , in close agreement with the theoretical estimates.

Nuclear reactions of silver with 0.8-TeV protons

C. F. Wang and N. T. Porile

Phys. Rev. C 33, 2183 (1986) - Published 1 June, 1986

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Cross sections for the formation of radionuclides in the interaction of silver with 0.8 TeV protons have been measured. The results are compared with previously reported data obtained for 300 GeV protons. The ratios of cross sections at the two energies are consistent with unity and are independent of product mass number between A=7 and 105.

Valence proton orbit radii and total rms charge radii in the tin region

Rupayan Bhattacharya

Phys. Rev. C 33, 2185 (1986) - Published 1 June, 1986

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Orbit radii of 1 $g_{9 / 2}$ , 2 $p_{1 / 2}$ , and 2 $p_{3 / 2}$ proton orbitals of even isotopes of tin and their total charge radii have been investigated through an optimized average one-body potential. Fairly good agreement with the experimental results has been obtained. Constancy of orbit radii with separation energy, in contradiction to Moalem’s observation, has been achieved.

Effect of variation of the single particle energies in the structure of N=82 isotones

Y. K. Gambhir and J. A. Sheikh

Phys. Rev. C 33, 2188 (1986) - Published 1 June, 1986

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The single particle energies extracted through the inverse gap equation method for each nucleus are used in the nuclear structure calculations within the framework of the broken pair approximation for N=82 even isotones. This makes a modest improvement of the trend of the level energies with particle number as compared to those obtained by using a fixed set of the single particle energies.

Collective flow in Ar+KCl at 1.8 GeV/nucleon

H. R. Jaqaman

Phys. Rev. C 33, 2191 (1986) - Published 1 June, 1986

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The failure of the standard sphericity tensor analysis to detect any significant collective flow effect in Ar+KCl at 1.8A GeV is examined in light of the success of the transverse momentum analysis technique suggested by Danielewicz and Odyniec in exhibiting collective flow in the same system. It is argued, using a simple estimate which takes into consideration the main features of the data, that the failure of the sphericity analysis is attributable to the dominant contribution of the longitudinal momentum of the spectators which has nothing to do with the collective effects for which sphericity analysis is designed. The exclusion of the spectators from the sphericity tensor leads to a clear signal from the collective transverse flow of the participants whenever such a flow takes place.

Nuclear wave function considerations in pion photoproduction

M. K. Singham

Phys. Rev. C 33, 2194 (1986) - Published 1 June, 1986

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We find that the measured values of the angular distributions for the reaction ${}^{13}{(γ}$ , $π^{+}$ $)^{13}$ B ${}_{g . s .}$ can be reasonably well reproduced provided that (i) nuclear wave functions constrained to fit a wide range of weak and electromagnetic data are used and (ii) the Δ-isobar term in the Blomqvist-Laget photoproduction operator is omitted. All calculations were done in the 1p-shell model space, suggesting that core polarization contributions are much smaller than previously estimated.

${}^{26}{Al}$ (n,p $)^{26}$ Mg reaction: Comparison between the Hauser-Feshbach formula and the exact random-matrix result for the cross section

J. Thomas, M. R. Zirnbauer, and K. Langanke

Phys. Rev. C 33, 2197 (1986) - Published 1 June, 1986

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We have calculated the ${}^{26}{Al}$ (n,p $)^{26}$ Mg reaction rate using an exact expression for the compound-nucleus cross section derived recently by Verbaarschot et al. This reaction is astrophysically important, and it happens to fall in a kinematic regime where the exact expression is expected to yield large deviations from the standard Hauser-Feshbach formula. We find that the exact statistical cross section is 20% lower at energies greater than 300 keV, and drops to 40% lower at 0 energy but still does not describe the available data. These deviations are quite similar to those predicted by the formula of Tepel et al.

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Rotational band structure in ${}^{133}\Pr$

L. Hildingsson, C. W. Beausang, D. B. Fossan, and W. F. Piel, Jr.

Phys. Rev. C 33, 2200(R) (1986) - Published 1 June, 1986

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The level structure of the odd proton nucleus ${}^{133}\Pr$ has been investigated. Excited states up to spin frac452 have been observed. The yrast band, built on a decoupled $h_{\frac{11}{2}}$ proton, shows an up-bend at $ℏ ω = 0.43$ MeV when two additional $h_{\frac{11}{2}}$ protons align. Two positive parity side bands, based on the $g_{\frac{7}{2}} {\frac{5}{2}}^{+} [413]$ proton configuration, are established with opposite signature. Both show a band crossing at $ℏ ω_{c} = 0.27$ MeV with a gain in $alignment \approx 8 ℏ$ , when two $h_{\frac{11}{2}}$ protons decouple. This low crossing frequency is partly explained by a reduction in the proton pairing gap caused by the $g_{\frac{7}{2}}$ proton.

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${}^{4}H$ and ( $n, α x$ ) reactions on ${}^{6}{Li}$ and ${}^{7}{Li}$

Đ. Miljanić, S. Blagus, and M. Zadro

Phys. Rev. C 33, 2204(R) (1986) - Published 1 June, 1986

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The cross sections for the ${}^{6}{Li} (n, α x)$ and ${}^{7}{Li} (n, α x)$ reactions have been measured by the detection of $α$ particles in coincidence with other charged particles ( $x$ ). Prominent structures in the coincident $α$ -particle energy spectra have been observed only in the case of ${}^{7}{Li}$ . They could be attributed to the processes involving the states of ${}^{4}H$ .

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Thermalization in ultrarelativistic heavy ion collisions: Parton cascade approach

David H. Boal

Phys. Rev. C 33, 2206(R) (1986) - Published 1 June, 1986

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A parton cascade model is formulated for ultrarelativistic heavy ion collisions. The model is used to determine the degree of thermalization, as well as energy and baryon number densities in central collisions of heavy ions at ultrarelativistic energies. It is shown that the energy densities required for quark-gluon plasma formation can easily be reached at $\sqrt{s_{NN}}$ less than 100 GeV.

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Application of a hot spot model to fragment emission from pion true absorption

R. A. Loveman

Phys. Rev. C 33, 2209(R) (1986) - Published 1 June, 1986

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This paper describes the application of a "hot spot" statistical model to the process of pion-induced fragmentation. In other reactions the spectra of pre-equilibrium particles are well described by the evaporation of particles from highly excited subsystems evolving within a cold nuclear system. The model is found to be very successful at describing both the ${}^{3}{He}$ and ${}^{4}{He}$ spectra from 160 MeV positive pion absorption on silver and is the first successful application of a statistical model to pion-induced emission of complex particles. The implications this has for the process of pion true absorption are examined.

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Solar neutrinos from the decay of ${}^{8}B$

Distortion in the β-decay spectrum for low electron kinetic energies

${}^{234}U$ excited states fed in the β decay of ${}^{234}{Pa}$

Decay of 7.3-min ${}^{235}{Th}$ and 24.6-min ${}^{235}{Pa}$

Characterization of isomers in ${}^{158}{Ho}$

Half-life limit for ${}^{48}{Ca}$ (2 $β^{-}$ $)^{48}$ Ti( $0_{2}^{+}$ ,2997)

Mechanism of pion double charge exchange at $T_{π}$ =292 MeV

K-shell ionization in the beta decay of ${}^{141}{Ce}$

Magnetic moment and lifetime of the 127 keV state in ${}^{101}{Ru}$

Spin-dipole isovector resonances in ${}^{12}C$ and ${}^{6}{Li}$ by positive photopion production

Nuclear reactions of silver with 0.8-TeV protons

Valence proton orbit radii and total rms charge radii in the tin region

Effect of variation of the single particle energies in the structure of N=82 isotones

Collective flow in Ar+KCl at 1.8 GeV/nucleon

Nuclear wave function considerations in pion photoproduction

${}^{26}{Al}$ (n,p $)^{26}$ Mg reaction: Comparison between the Hauser-Feshbach formula and the exact random-matrix result for the cross section

Rotational band structure in ${}^{133}\Pr$

${}^{4}H$ and ( $n, α x$ ) reactions on ${}^{6}{Li}$ and ${}^{7}{Li}$

Thermalization in ultrarelativistic heavy ion collisions: Parton cascade approach

Application of a hot spot model to fragment emission from pion true absorption

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