Recent Articles

Proton-unbound states in ${}^{41}K$

L. R. Medsker, H. T. Fortune, and S. C. Headley

Phys. Rev. C 12, 401 (1975) - Published 1 August, 1975

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The ${}^{40}{Ar} ({}^{3}{He}, d)$ reaction, at 18 MeV ${}^{3}{He}$ energy, has been used to study states in ${}^{41}K$ that are unbound to proton emission. The ${}^{40}{Ar}$ target was contained in a gas cell with no entrance window. Excitation energies and angular distributions were obtained for levels from $E_{x} = 7.836 to 10.239$ MeV. A distorted-wave analysis was used to determine $l$ values and to extract widths $Γ_{p}$ for comparison with the results of previous ${}^{40}{Ar} (p, p)$ work. The analog of the ground state of ${}^{41}{Ar}$ , at 8.349 MeV excitation in ${}^{41}K$ , and six excited-state analogs were observed.

NUCLEAR REACTIONS ${}^{40}{Ar} ({}^{3}{He}, d)$ , $E = 18$ MeV; measured $σ (E_{d}, θ)$ ; deduced ${}^{41}K$ unbound states, $l$ , $Γ_{p}$ , $C^{2} S_{lj}$ .

Neutron capture in laser-fusion pellets

John Henley and Heiner W. Meldner

Phys. Rev. C 12, 407 (1975) - Published 1 August, 1975

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Investigating the feasibility of obtaining slow neutron fluencies sufficient for multiple-capture nucleosynthesis, we have applied a Monte Carlo technique to determine the moderation of neutrons in a superdense laser-energized fusion pellet. We studied pellets of varying chemical composition and structure ranging in size from $ρ R \sim 1 to 50$ g/ ${cm}^{2}$ and found our results to be rather insensitive to the parametrization of the hydrodynamic motion. That is, the neutron spectra were largely unaffected by reasonable variations of peak density, time of disassembly, and shape of the density profile. A useful method of improving the ratio of moderated to unmoderated neutrons was to dilute the thermonuclear fuel with hydrogen and/or the addition of a beryllium reflector. We also calculated the ratio of fission, neutron capture, and ( $n, p$ ) reactions in pellets seeded with traces of ${}^{238}U$ target material.

NUCLEAR REACTIONS Calculated neutron fluxes and neutron-nucleus reactions for parametrized thermonuclear explosions of ${}^{2}H$ ${}^{3}H$ and ${}^{2}H$ ${}^{2}H$ laser-fusion pellets with moderators and target material.

Independent fission yields of Rb and Cs from thermal-neutron-induced fission of ${}^{239}{Pu}$

Silvio J. Balestrini and Leon Forman

Phys. Rev. C 12, 413 (1975) - Published 1 August, 1975

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The relative independent fission yields of Rb and Cs from thermal-neutron-induced fission of ${}^{239}{Pu}$ have been measured on line using a mass spectrograph and thermalized neutrons from a burst reactor. Independent yields were derived by normalizing the measurements to products of chain yields and fractional independent yields, estimating the latter from measured cumulative yields of Kr and Xe. Comparing the independent yields with those from ${}^{238}U$ fission, the ${}^{239}{Pu}$ results show shifts in isotopic yield distribution toward lower mass for both Rb and Cs and also toward the production of more Cs and less Rb when ${}^{239}{Pu}$ is fissioned.

NUCLEAR REACTIONS ${}^{209}{Pu} (n, f)$ , $E = thermal$ ; measured relative abundances; deduced independent fission yields. Mass spectrograph, burst reactor.

Spectroscopy of ${}^{146}{Sm}$ via the ( $d, t$ ) and of ${}^{148}{Sm}$ via the ( $d, t$ ) and ( $d, p$ ) reactions

W. Oelert, J. V. Maher, D. A. Sink, and M. J. Spisak

Phys. Rev. C 12, 417 (1975) - Published 1 August, 1975

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The ( $d, t$ ) reaction on the isotopes ${}^{147}{Sm}$ and ${}^{149}{Sm}$ has been investigated at a deuteron energy of 17 MeV; the ( $d, p$ ) reaction on the isotope ${}^{147}{Sm}$ at a deuteron energy of 12.5 MeV. Angular distributions were taken in 2.5° steps in the range of $7.5 \leq θ_{lab} \leq 35 °$ and in 5° steps for $θ_{lab} > 35 °$ . The experimental energy resolution is 9-11 keV for the pickup reactions and 10-12 keV for the stripping case. Spectroscopic factors and $l$ transfers were extracted by distorted wave Born approximation analysis. Eighty-three states in ${}^{146}{Sm}$ are observed; $l$ transfer and $J^{π}$ limits are given for 36 of them. For the nucleus ${}^{148}{Sm}$ 97 states are observed; $l$ transfers and $J^{π}$ limits are given for 63 of them. Reasonable $l = 3$ , $l = 1$ , and $l = 0$ summed strengths have been found. Comparison with ( $p, t$ ) and ( $t, p$ ) studies of the same final nuclei investigated here is made in a phenomenological collective picture.

NUCLEAR REACTIONS ${}^{147}{Sm} (d, t)$ and ${}^{149}{Sm} (d, t)$ , $E_{d} = 17$ MeV. ${}^{147}{Sm} (d, p)$ , $E_{d} = 12.5$ MeV. Measured $σ (E_{t}, θ)$ , $σ (E_{p}, θ)$ ; ${}^{146, 148}{Sm}$ level energies, resolution 9-12 keV, enriched targets, DWBA analysis.

Particle-phonon interactions in ${}^{248}{Cf}$ and ${}^{249}{Cf}$

S. W. Yates, R. R. Chasman, A. M. Friedman, I. Ahmad, and K. Katori

Phys. Rev. C 12, 442 (1975) - Published 1 August, 1975

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The extent of particle-photon mixing in ${}^{248}{Cf}$ and ${}^{249}{Cf}$ has been determined using the ${}^{249}{Cf} (d, t)$ and ${}^{249}{Cf} (d, d^{'})$ reactions. $K^{π} = 2^{-}$ bands were identified at 593 and 1477 keV in ${}^{248}{Cf}$ . Since the only $K^{π} = 2^{-}$ neutron two quasiparticle configuration expected below 2 MeV in ${}^{248}{Cf}$ is ${{\frac{9}{2}}^{-} [734]; {\frac{5}{2}}^{+} [622]}_{2 -}$ , the second $K^{π} = 2^{-}$ band is considered to be predominantly of phonon character. In ${}^{249}{Cf}$ a $K^{π} = {\frac{5}{2}}^{+}$ band at 145 keV, known from decay scheme studies, receives a measurable population in the ( $d, d^{'}$ ) reaction. The phonon admixture in the ${\frac{5}{2}}^{+}$ state which results from the ${{\frac{9}{2}}^{-} [734] \otimes 2^{-} phonon}$ configuration was determined to be (29±5)%. The collective admixture in the ${\frac{5}{2}}^{+}$ state was also calculated from an octupole particle-hole interaction and was found to be 35%, in good agreement with the experimental value. The anomalously low energy of the ${\frac{5}{2}}^{+}$ state could not be entirely reproduced by this calculation.

NUCLEAR REACTIONS ${}^{249}{Cf} (d, d^{'})$ , $E_{d} = 15$ MeV; ${}^{249}{Cf} (d, t)$ , $E_{d} = 12$ MeV; measured $σ (θ)$ . ${}^{248}{Cf}$ , ${}^{249}{Cf}$ deduced levels, $J$ , $π$ , extracted phonon contributions. Enriched target. Calculated particle-phonon mixing.

Cross sections for ( $n, xn$ ) reactions between 7.5 and 28 MeV

B. P. Bayhurst, J. S. Gilmore, R. J. Prestwood, J. B. Wilhelmy, Nelson Jarmie, B. H. Erkkila, and R. A. Hardekopf

Phys. Rev. C 12, 451 (1975) - Published 1 August, 1975

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A total of 236 cross sections for ( $n, xn$ ) reactions have been measured at neutron energies between 7.5 and 28 MeV, using radiochemical techniques. Cross sections for ( $n, n^{'}$ ) and ( $n, 2 n$ ) reactions are reported on ${}^{193}{Ir}$ ; ( $n, 2 n$ ) cross sections on ${}^{45}{Sc}$ and ${}^{58}{Ni}$ ; ( $n, 2 n$ ) and ( $n, 3 n$ ) cross sections on ${}^{89}Y$ , ${}^{90}{Zr}$ , and ${}^{107}{Ag}$ ; ( $n, 2 n$ ), ( $n, 3 n$ ), and ( $n, 4 n$ ) cross sections on ${}^{169}{Tm}$ , ${}^{175}{Lu}$ , ${}^{191}{Ir}$ , ${}^{197}{Au}$ , and ${}^{203}{Tl}$ ; ( $n, 3 n$ ) and ( $n, 4 n$ ) cross sections on ${}^{151}{Eu}$ ; and ( $n, 4 n$ ) cross sections on ${}^{205}{Tl}$ . Neutron fluences were determined by either the ${}^{27}{Al} (n, α) {}^{24}{Na}$ or the ${}^{90}{Zr} (n, 2 n) {}^{89}{Zr}$ reactions appropriately combined with proton-recoil telescope measurements. The excitation functions are compared with calculations based on a model incorporating both compound-nucleus and preequilibrium decay modes. Cross sections for the ${}^{27}{Al} (n, α) {}^{24}{Na}$ reaction between 21 and 26 MeV are also reported.

NUCLEAR REACTIONS ${}^{27}{Al} (n, α)$ , $E = 21.4 - 4 - 26.0$ MeV; ${}^{45}{Sc} (n, 2 n)$ , $E = 14.1 - 28.1$ MeV; ${}^{58}{Ni} (n, 2 n)$ , $E = 16.2 - 28.1$ MeV; ${}^{89}Y (n, 2 n)$ , ( $n, 3 n$ ), $E = 14.1 - 28.1$ MeV; ${}^{107}{Ag} (n, 2 n)$ , ( $n, 3 n$ ), $E = 13.4 - 28.1$ MeV; ${}^{151}{Eu} (n, 3 n)$ , ( $n, 4 n$ ) $E = 14.8 - 28.0$ MeV; ${}^{169}{Tm} (n, 2 n)$ , ( $n, 3 n$ ), ( $n, 4 n$ ), $E = 8.6 - 28.0$ MeV; ${}^{191}{Ir} (n, 2 n)$ , $E = 8.6 - 24.5$ MeV; ${}^{191}{Ir} (n, 3 n)$ , ( $n, 4 n$ ), $E = 16.2 - 28.0$ MeV; ${}^{193}{Ir} (n, n)$ , $E = 7.6 - 14.7$ MeV; ${}^{193}{Ir} (n, 2 n)$ , $E = 8.6 - 21.2$ MeV; ${}^{197}{Au} (n, 2 n)$ , ( $n, 3 n$ ), ( $n, 4 n$ ), $E = 8.6 - 28.1$ MeV; ${}^{203}{Ti} (n, 2 n)$ , ( $n, 3 n$ ), ( $n, 4 n$ ), $E = 8.6 - 28.0$ MeV; ${}^{205}{Tl} (n, 4 n)$ , $E = 23.3 - 28.0$ MeV; $Zr (n, x n)$ , $E = 14.1 - 28.1$ MeV; $Lu (n, x n)$ , $E = 8.5 - 28.0$ MeV; measured $σ (E)$ . Estimated ${}^{90}{Zr} (n, 2 n)$ , ( $n, 3 n$ ), ${}^{175}{Lu} (n, 2 n)$ , ( $n, 3 n$ ), ( $n, 4 n$ ), $σ (E)$ . Comparison with combined statistical and preequilibrium model.

RADIOACTIVITY ${}^{189, 190}{Ir}$ , ${}^{193}{Ir}^{m}$ ; measured $T_{\frac{1}{2}}$ .

Yrast levels in ${}^{44}{Ti}$

J. J. Simpson, W. Dünnweber, J. P. Wurm, P. W. Green, J. A. Kuehner, W. R. Dixon, and R. S. Storey

Phys. Rev. C 12, 468 (1975) - Published 1 August, 1975

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The reaction ${}^{32}S ({}^{14}N, pn γ) {}^{44}{Ti}$ has been studied with a view to populating high spin states in ${}^{44}{Ti}$ . In singles and $γ - γ$ coincidence experiments $γ$ -ray transitions in the ground state band and a negative parity band are seen and three levels connected to the ground state band, at 6508, 7671, and 8040 keV, are inferred. Angular distributions are consistent with stretched cascades. The lifetime of the 7671-keV level, presumed $10^{+}$ , has been determined by the attenuated Doppler-shift method to be 2.7 ± 0.5 ps. A comparison of the present reaction with the recently reported ${}^{28}{Si} ({}^{19}F, p 2 n γ) {}^{44}{Ti}$ reaction is made and a method for predicting the propensity of these types of reaction to feed high spin states is proposed. $An {(fp)}^{4}$ shell model calculation of yrast levels up to $J = 12$ has been made.

NUCLEAR REACTIONS ${}^{32}S ({}^{14}N, pn γ)$ , $E = 26 - 43$ MeV; measured $γ - γ$ coin and $σ (E)$ ; ${}^{44}{Ti}$ deduced levels; measured $W (θ_{γ})$ , Doppler-shift attenuation; deduced $J^{π}$ , $T_{\frac{1}{2}}$ . Natural targets, Ge(Li) detectors.

Structure of ${}^{7}{Be}$ and ${}^{63}{Cu}$ determined from the ${}^{63}{Cu}$ ( ${}^{6}{Li}$ , ${}^{7}{Be}$ ) ${}^{62}{Ni}$ reaction

G. M. Hudson, K. W. Kemper, G. E. Moore, and M. E. Williams

Phys. Rev. C 12, 474 (1975) - Published 1 August, 1975

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Angular distributions have been measured for the reaction ${}^{63}{Cu}$ ( ${}^{6}{Li}$ , ${}^{7}{Be}_{0, 1}$ ) ${}^{62}{Ni}_{0, 1}$ at $E ({}^{6}{Li}) = 34$ MeV in the angular range 2-52.5° (lab). Exact finite-range distorted-wave-Born-approximation (DWBA) calculations were not able to reproduce the shape of the angular distributions even though similar calculations with the same optical model parameters were able to describe the ${}^{62}{Ni}$ ( ${}^{7}{Li}$ , ${}^{6}{He}$ ) ${}^{63}{Cu}$ reaction. Elastic scattering data for ${}^{7}{Li}$ + ${}^{62}{Ni}$ and ${}^{6}{Li}$ + ${}^{63}{Cu}$ were reanalyzed with the optical model assuming a real radius given by $R = 1.2 {A_{T}}^{\frac{1}{3}}$ instead of the previously used $R = 1.2 ({A_{T}}^{\frac{1}{3}} + {A_{P}}^{\frac{1}{3}})$ . The optical model fits to the elastic scattering data and the finite-range DWBA calculations for the ${}^{62}{Ni}$ ( ${}^{7}{Li}$ , ${}^{6}{He}$ ) reaction data were equivalent with both optical parameter sets while the ${}^{63}{Cu}$ ( ${}^{6}{Li}$ , ${}^{7}{Be}$ ) fit was greatly improved. The shape of the forward angle ${}^{63}{Cu}$ ( ${}^{6}{Li}$ , ${}^{7}{Be}_{0, 1}$ ) ${}^{62}{Ni}_{0}$ data indicates that ${}^{7}{Be}_{1}$ has a larger $\frac{1 p_{\frac{3}{2}}}{1 p_{\frac{1}{2}}}$ ratio than found in the ground state of ${}^{7}{Be}$ . Ratios of $\frac{1 p_{\frac{3}{2}}}{1 p_{\frac{1}{2}}}$ strengths in ${}^{7}{Be}_{0, 1}$ extracted by fitting the shape of the forward angle data with finite-range DWBA calculations of the cross sections are in excellent agreement with the calculations of Cohen and Kurath. In addition, the spectroscopic factor for ${}^{63}{Cu}$ is in good agreement with values found from other reactions when the Cohen and Kurath results for ${}^{7}{Be}$ are assumed. The spectroscopic factor for the component in the ${}^{63}{Cu}$ ground state wave function which corresponds to ${}^{62}{Ni} (2^{+}) \otimes 2 p_{\frac{3}{2}}$ has also been extracted. An upper limit for the magnitude of the cross section for the reaction ${}^{63}{Cu}$ ( ${}^{6}{Li}$ , ${}^{9}{Be}$ ) has been determined.

NUCLEAR REACTIONS ${}^{63}{Cu}$ ( ${}^{6}{Li}$ , ${}^{7}{Be}$ ) measured $σ (θ)$ at $E ({}^{6}{Li}) = 34$ MeV for $θ = 2 - 52.5 °$ , $Δ θ = 2.5 °$ . Deduced $S ({}^{62}{Ni}_{0, 1})$ and $S ({}^{7}{Be}_{0, 1})$ from finite-range DWBA analysis. ${}^{63}{Cu}$ ( ${}^{6}{Li}$ , ${}^{9}{Be}$ ) measured $σ$ at 15, 20, and 25°.

Mass and energy distributions of fusion products from ${}^{32}S$ on ${}^{12}C$ , ${}^{25}{Mg}$ , and ${}^{40}{Ca}$

J. D. Garrett, H. E. Wegner, T. M. Cormier, E. R. Cosman, and A. J. Lazzarini

Phys. Rev. C 12, 481 (1975) - Published 1 August, 1975

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The mass and energy distributions for fusion products corresponding to 128.9 MeV ${}^{32}S$ on ${}^{12}C$ , ${}^{25}{Mg}$ , and ${}^{40}{Ca}$ targets has been measured at 8° lab using a time-of-flight spectrometer. The heaviest product observed with significant cross section for each system has a mass five units less than that of the corresponding compound system. Lighter dominant mass groups are separated by approximately three mass units. Such mass systematics can be understood in terms of neutron, proton, and $α$ -particle competition in the deexcitation of the compound system and are reproduced qualitatively by particle evaporation calculations.

NUCLEAR REACTIONS ${}^{32}S$ + ${}^{12}C$ , ${}^{25}{Mg}$ , ${}^{40}{Ca}$ fusion, $E = 128.9$ MeV; measured mass and energy distribution of products.

Elastic scattering and transfer reactions induced by 100 MeV ${}^{32}S$ on ${}^{27}{Al}$

J. D. Garrett, H. E. Wegner, T. M. Cormier, E. R. Cosman, Ole Hansen, and A. J. Lazzarini

Phys. Rev. C 12, 489 (1975) - Published 1 August, 1975

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Angular distributions have been obtained at an incident energy of 100 MeV corresponding to ${}^{32}S$ elastic scattering on ${}^{27}{Al}$ , ${}^{27}{Al}$ ( ${}^{32}S$ , ${}^{31}P$ ) transitions to the ground and first-excited states of ${}^{28}{Si}$ and ${}^{27}{Al}$ ( ${}^{32}S$ , ${}^{33}S$ ) transitions to an unresolved group of low-lying states in ${}^{26}{Al}$ . An optical model analysis of the elastic data shows that the "best fit" potentials with constant diffusivity follow the $V e^{\frac{R}{a}} = constant$ ambiguity extremely well. It appears that the elastic data is most sensitive to the ion-ion potential near a radius of ≈ 10.1 fm. The absolute cross sections of the ${}^{27}{Al}$ ( ${}^{32}S$ , ${}^{31}P$ ) transitions to the ground and first-excited states of ${}^{28}{Si}$ are well reproduced in a distorted-wave Born-approximation analysis using optical model parameters which reproduce elastic scattering. The angular positions of the ( ${}^{32}S$ , ${}^{31}P$ ) grazing peaks, however, are observed a few degrees forward of their predicted position, and the measured cross sections forward of the grazing peaks are considerably larger than predicted. The agreement between measured and predicted angular shape apparently is better for the ${}^{27}{Al}$ ( ${}^{32}S$ , ${}^{33}S$ ) ${}^{26}{Al}$ neutron transfer than for the proton transfer data. From this limited first data for ${}^{32}S$ induced reactions it appears that such reactions can be explained to the extent that "lighter heavy-ion" induced reactions are understood.

NUCLEAR REACTIONS ${}^{32}S$ + ${}^{27}{Al}$ elastic scattering; $E = 100$ MeV, measured $σ (θ)$ ; optical model analysis, extracted optical model parameters. ${}^{27}{Al}$ ( ${}^{32}S$ , ${}^{31}P$ ) and ${}^{27}{Al}$ ( ${}^{32}S$ , ${}^{33}S$ ); $E = 100$ MeV, measured $σ (θ)$ ; DWBA analysis, extracted spectroscopic factors.

Gamma-ray linear polarization measurements following heavy-ion bombardment of odd isotopes of Pd

Jin Soon Kim, Y. K. Lee, K. A. Hardy, P. C. Simms, J. A. Grau, G. J. Smith, and F. A. Rickey

Phys. Rev. C 12, 499 (1975) - Published 1 August, 1975

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$γ$ -ray linear polarization measurements have been used to locate negative parity states in the even-odd isotopes ${}^{99, 101, 103}{Pd}$ . A Compton polarimeter based on two Ge(Li) coaxial detectors was used. Collective bands ( $I = {\frac{11}{2}}^{-}, {\frac{15}{2}}^{-}, {\frac{19}{2}}^{-}, \dots$ ) built on ${\frac{11}{2}}^{-}$ states were observed in ${}^{101}{Pd}$ and ${}^{103}{Pd}$ . Many negative parity states were also observed in ${}^{99}{Pd}$ , but they do not appear to be part of a similar collective band. These polarization measurements also confirm many angular momentum assignments which previously had been made using systematic arguments.

NUCLEAR REACTIONS ${}^{90, 92, 94}{Zr} ({}^{12}C, 3 n)$ , $E = 48 - 56$ MeV; measured linear polarization of $γ$ rays; parities and multipole mixing ratios in ${}^{99, 101, 103}{Pd}$ transitions deduced.

$π^{+} + nucleus \to K^{+} + hypernucleus$ in the impulse approximation

S. Calzavara and L. H. Schick

Phys. Rev. C 12, 507 (1975) - Published 1 August, 1975

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The impulse approximation and some crude nuclear and hypernuclear wave functions are used to calculate cross sections for some reactions of the type $π^{+} + nucleus \to K^{+} + hypernucleus$ for incident $π^{+}$ laboratory energies in the range 0.55-1.0 GeV. Target nuclei considered were ${}^{4}{He}$ , ${}^{7}{Li}$ , and ${}^{119}{Sn}$ . Cross sections (or cross sections per nucleon) were calculated for production of the ground states and some possible excited states of the resultant hypernuclei. Although some results are marginal, on the whole the calculated cross sections appear to be too small for this to be a useful production method for hypernuclei at the pion energies available at present meson factories.

NUCLEAR REACTIONS Production of hypernuclei, $π^{+}$ on ${}^{4}{He}$ , ${}^{7}{Li}$ , ${}^{119}{Sn}$ , $T_{π} = 0.55 - 1.0$ GeV.

Pion photoproduction at threshold on ${}^{6}{Li}$ and low-energy theorems

Matías Moreno, Jean Pestieau, and Jesús Urías

Phys. Rev. C 12, 514 (1975) - Published 1 August, 1975

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The Low, Kroll-Ruderman, and Fubini-Furlan-Rossetti theorems are derived in the case of pion photoproduction on ${}^{6}{Li}$ . Particular care has been taken to be consistent with electromagnetic current conservation and Low's theorem in the extrapolation from soft to real pions. This is new compared to previous treatments of soft pion theorems in nuclear processes where one photon is present. Difficulties due to the spin-1 nature of ${}^{6}{Li}$ have been put forward.

NUCLEAR REACTIONS Low, Kroll-Ruderman, Fubini-Furlan-Rossetti theorems for ${}^{6}{Li} (γ, π^{+}) {}^{6}{He}$ .

No-resonance condition for a ${}^{1}S_{0}$ separable $Λ N$ potential with suppression effects

L. H. Schick

Phys. Rev. C 12, 523 (1975) - Published 1 August, 1975

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Two-channel $Λ N$ potentials each of whose matrix elements is a single nonlocal separable are discussed. A simpler condition than obtained previously is derived for the $Λ$ - channel shape such that the $Λ N$ scattering length and effective range agree with the values obtained from a meson-theoretic potential both with the $Σ$ channel unsuppressed and fully suppressed and which at the same time guarantees the absence of an unwanted $Λ N$ resonance below the $Σ$ -channel threshold due to a bound state in the uncoupled $Σ$ channel. A specific nonlocal separable shape is exhibited which obeys this condition for a range of values of its parameters when the most recent ${}^{1}S_{0}$ meson-theoretic potential scattering lengths and effective ranges of Brown, Downs, and Iddings are used as input.

NUCLEAR REACTIONS $YN$ potential, $Λ N$ scattering length and effective range, two-channel separable potential, $Λ N \to Σ N$ suppression, $Λ N$ resonance.

Li, Be, and B production in the 3-GeV proton bombardment of Ni

G. M. Raisbeck, P. Boerstling, R. Klapisch, and T. D. Thomas

Phys. Rev. C 12, 527 (1975) - Published 1 August, 1975

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Measurements have been made of the energy spectra and angular distributions of Li, Be, and B nuclei emitted from a Ni target bombarded with 3-GeV protons, using a counter telescope technique. By integrating the spectra and normalizing to the radiochemically determined cross section of ${}^{7}{Be}$ , total isotopic cross sections have been determined, and these are discussed in terms of the cosmic ray production of Li, Be, and B. The experimental cross sections are compared with a recent semiempirical formula; within the uncertainties the agreement between experiment and prediction is satisfactory.

NUCLEAR REACTIONS Ni with 3-GeV protons; measured energy spectra, angular distributions, yields for Li, Be, and B isotopes.

Production and investigation of tungsten $α$ emitters including the new isotopes, ${}^{165}W$ and ${}^{166}W$

K. S. Toth, W. -D. Schmidt-Ott, C. R. Bingham, and M. A. Ijaz

Phys. Rev. C 12, 533 (1975) - Published 1 August, 1975

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Neutron-deficient tungsten isotopes were produced by bombarding an enriched ${}^{156}{Dy}$ target with ${}^{16}O$ ions accelerated in the Oak Ridge isochronous cyclotron. A gas-jet-capillary system was used to transport product nuclei to an area where their $α$ -decay properties could be investigated. The data of Eastham and Grant concerning ${}^{162, 163, 164}W$ were confirmed. In addition, two new weak $α$ groups were observed. On the basis of excitation functions, ${}^{14}N$ + ${}^{156}{Dy}$ cross bombardments, and $α$ -decay energy systematics they were assigned to the new isotopes ${}^{165}W$ and ${}^{166}W$ . Their decay properties are as follows: (1) ${}^{165}W$ , $E_{α} = 4.909 \pm 0.005$ MeV, $T_{\frac{1}{2}} = 5.1 \pm 0.5$ sec, and (2) ${}^{166}W$ , $E_{α} = 4.739 \pm 0.005$ MeV, $T_{\frac{1}{2}} = 16 \pm 3$ sec.

RADIOACTIVITY ${}^{162, 163, 164, 165, 166}W$ ; measured $E_{α}$ , $T_{\frac{1}{2}}$ ; discovered new isotopes ${}^{165, 166}W$ .

Levels in ${}^{237}{Pu}$ populated by ${}^{237}{Am}$ (electron capture) and ${}^{241}{Cm} (α)$ decays

I. Ahmad, F. T. Porter, M. S. Freedman, R. K. Sjoblom, J. Lerner, R. F. Barnes, J. Milsted, and P. R. Fields

Phys. Rev. C 12, 541 (1975) - Published 1 August, 1975

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The electron capture decay scheme of ${}^{237}{Am}$ (73 min) has been investigated by measuring the $γ$ -ray and conversion-electron spectra of mass-separated ${}^{237}{Am}$ samples. The $γ$ -ray spectra were measured with a Ge(Li) spectrometer and the conversion-electron spectra were measured with a cooled Si(Li) detector and a magnetic $β$ -ray spectrometer. Thirty-five $γ$ rays were identified and the multipolarities of most of the transitions were deduced. The half-life of ${}^{237}{Am}$ was determined by following the decay of the 280.2 keV photopeak and was found to be 73.0 ± 1.0 min. The $α$ -particle energy and $α$ branching were measured to be 6.042 ± 0.005 MeV and [(2.5 ± 0.3) × $10^{- 2}$ ]%, respectively. On the basis of the present investigation the following single-particle states have been identified in ${}^{237}{Pu}$ : $\frac{7}{2} - [743], 0$ ½+[631], 145.5; $\frac{5}{2} + [622], 280.2$ ; $\frac{3}{2} + [631], 370.4$ ; $\frac{5}{2} + [633], 407.8$ ; $\frac{7}{2} + [624], 473.5$ ; $\frac{5}{2} - [752], 655.3$ ; and $\frac{7}{2} + [613], 908.8$ keV. The ground state of ${}^{237}{Am}$ has been deduced to be the $\frac{5}{2} - [523]$ Nilsson orbital. The $log ft$ values for electron capture transitions to the observed states were derived. The $α$ -particle spectrum of a mass-separated ${}^{241}{Cm}$ sample was measured with the Argonne double focusing magnetic spectrometer. Eleven $α$ groups identified in this spectrum populate the members of the ground state, ½+[631], and $\frac{3}{2} + [631]$ bands. The $α$ -decay hindrance factors are consistent with the Nilsson-state assignments deduced from ${}^{237}{Am}$ electron capture decay.

RADIOACTIVITY ${}^{237}{Am}$ [from ${}^{237}{Np} (α, 4 n)$ and ${}^{237}{Np} ({}^{3}{He}, 3 n)$ )]; measured $T_{\frac{1}{2}}$ , $E_{α}$ , $E_{γ}$ , $I_{γ}$ , $E_{ce}$ , $I_{ce}$ , $γ γ$ - coin, $α$ branching, ${}^{241}{Cm}$ [from ${}^{239}{Pu} (α, 2 n)$ ]; measured $E_{α}$ , $I_{α}$ ; deduced hindrance factors. ${}^{237}{Pu}$ deduced levels $log ft$ , (EC) $γ$ multipolarity, $I$ , $π$ , eight single-particle states. Mass-separated ${}^{237}{Am}$ and ${}^{241}{Cm}$ . Toroidal $β$ spectrometer at 0.15% FWHM.

Structure of ${}^{142}{Sm}$ from the decay of ${}^{142}{Eu}$

G. G. Kennedy, S. C. Gujrathi, and S. K. Mark

Phys. Rev. C 12, 553 (1975) - Published 1 August, 1975

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${}^{142}{Eu}$ has been observed to have two isomers with half-lives 1.22 ± 0.22 min ( ${}^{142}{Eu}^{m}$ ) and 2.4 ± 0.2 sec ( ${}^{142}{Eu}^{g}$ ), both of which decay by $β^{+}$ emission to states in ${}^{142}{Sm}$ , resulting in 32 and 8 $γ$ transitions, respectively. On the basis of $β^{+}$ and $γ$ ray singles and coincidence as well as conversion electron measurements, a level scheme comprising 20 excited states with deduced $J^{π}$ assignments has been constructed. Among the levels, a $5^{-}$ and a $7^{-}$ state at 2347.9 and 2372.0 keV, respectively, have been identified as two-quasiparticle neutron states. The half-life of the 2372.0 keV level has been measured to be 170 ± 2 ns using the $β^{+} - γ$ delayed coincidence technique. The $β^{+}$ end-point energy measurements yielded decay energies $Q_{EC} = 8.0 \pm 0.3 MeV and 8.15 \pm 0.10 MeV$ for ${}^{142}{Eu}^{g}$ and ${}^{142}{Eu}^{m}$ , respectively.

RADIOACTIVITY ${}^{142}{Eu}^{m, g}$ from ${}^{144}{Sm} (p, 3 n)$ ; measured $T_{\frac{1}{2}}$ , $E_{γ}$ , $I_{γ}$ , $I_{ce}$ , $E_{β^{+}}$ , $γ - γ$ coin, $γ - γ$ , $β - γ$ delay, deduced $Q_{EC}$ . ${}^{142}{Sm}$ deduced levels, $J$ , $π$ , $T_{\frac{1}{2}}$ , $log ft$ , ICC, $γ$ multipolarity. Enriched targets, Ge(Li), Si(Li), plastic, NaI(Tl) detectors.

Half-lives of some $T = \frac{1}{2}$ mirror decays

G. Azuelos and J. E. Kitching

Phys. Rev. C 12, 563 (1975) - Published 1 August, 1975

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Precision measurements of the half-lives of the decay of some $T = \frac{1}{2}$ mirror nuclei have been determined. The results are ${}^{11}C$ (1222.9 ± 1.2 sec), ${}^{19}{Ne}$ (17.219 ± 0.017 sec), ${}^{21}{Na}$ (22.47 ± 0.03 sec), ${}^{23}{Mg}$ (11.327 ± 0.014 sec), ${}^{25}{Al}$ (7.174 ± 0.007 sec), ${}^{27}{Si}$ (4.109 ± 0.004 sec), and ${}^{29}P$ (4.083 ± 0.012 sec). In addition, the half-life of ${}^{26}{Al}^{m}$ which proceeds by a pure Fermi decay, has been determined to be 6.346 ± 0.005 sec.

RADIOACTIVITY ${}^{11}C$ , ${}^{19}{Ne}$ , ${}^{21}{Na}$ , ${}^{23}{Mg}$ , ${}^{25}{Al}$ , ${}^{26}{Al}^{m}$ , ${}^{27}{Si}$ , ${}^{29}P$ ; measured $T_{\frac{1}{2}}$ ; calculated $ft$ .

$β$ decay of ${}^{43}{Sc}$

K. C. Young, Jr., S. L. Tabor, L. K. Fifield, and R. W. Zurmühle

Phys. Rev. C 12, 567 (1975) - Published 1 August, 1975

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The spectrum of $γ$ rays following the $β$ decay of ${}^{43}{Sc}$ has been measured with a 65 ${cm}^{3}$ Ge(Li) detector. $β$ -decay branches to the following states in ${}^{43}{Ca}$ were observed ( $log ft$ values in parentheses); ground state (5.03), 373 keV (4.97), and 1931 keV (5.66). The last $β$ -decay branch has not been previously reported. In contrast to earlier works, $β$ branches to the 593 ( $J^{π} = {\frac{3}{2}}^{-}$ ) and 990 keV ( $J^{π} = {\frac{3}{2}}^{+}$ ) levels were not observed and upper limits on these decay branches were obtained.

RADIOACTIVITY ${}^{43}{Sc}$ [from ${}^{40}{Ca} (α, p)$ ]; measured $E_{γ}$ , $I_{γ}$ ; deduced $log ft$ . ${}^{43}{Ca}$ deduced levels, $J$ , $π$ . Ge(Li) detector.

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