Recent Articles

Theory and experiment for the reaction ${}^{6}{Li} (e, d) e^{'}$ , ${}^{4}{He}$

D. M. Skopik, E. L. Tomusiak, E. T. Dressler, Y. M. Shin, and J. J. Murphy, II

Phys. Rev. C 14, 789 (1976) - Published 1 September, 1976

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Deuterons from the reaction ${}^{6}{Li} (e, d) e^{'}$ , ${}^{4}{He}$ were measured at eight laboratory angles over a deuteron energy interval of approximately 2-10 MeV. The incident electron energy was chosen so that only deuterons and $α$ particles were left in the final state. These data are compared to a one-resonance square-well electrodisintegration model. Extracted photodisintegration cross sections are also compared with a more sophisticated Woods-Saxon photodisintegration theory. In both comparisons the data and theory are in overall qualitative agreement.

NUCLEAR REACTIONS ${}^{6}{Li} (e, d) e^{'}$ , ${}^{4}{He}$ , measured $σ (E_{d}, θ_{d})$ , $E_{d} ≃ 2 - 10$ MeV, $θ = 30 - 150 °$ , extracted ${}^{6}{Li} (γ, d) {}^{4}{He}$ for $E_{x} > 10$ MeV.

Soft photon nucleon-nucleon bremsstrahlung in the potential model

F. Partovi

Phys. Rev. C 14, 795 (1976) - Published 1 September, 1976

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The soft photon theorem for bremsstrahlung has been derived nonrelativistically for two particles interacting via a nonlocal spin and isospin dependent potential. The result is in a simple form easily applicable to the special cases in which one or both particles have zero charge, spin, or isospin.

NUCLEAR REACTIONS $N (N, N γ)$ ; derived nucleon-nucleon bremsstrahlung amplitude in soft photon limit, potential model, including nonlocality spin and isospin.

Neutron spectrum at 0° from 83.7 MeV deuterons on beryllium

R. Madey, F. M. Waterman, and A. R. Baldwin

Phys. Rev. C 14, 801 (1976) - Published 1 September, 1976

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The neutron spectrum measured at 0° from 83.7 MeV deuteron bombardment of a thick beryllium target is bell-shaped with a peak at about 34 MeV and a full width at half maximum of about 22 MeV. Measurements down to 4 MeV show no indication of an evaporation peak. While the shape of the spectrum calculated on the basis of the Serber model for deuteron stripping is similar to the observed shape, the width of the calculated spectrum is broader than that observed. The broadening occurs primarily on the low-energy side of the spectrum. The same features are revealed in further calculations of the 0° spectrum from 53.8 MeV deuterons on a thick beryllium target.

NUCLEAR REACTIONS ${}^{9}{Be} (d, n)$ , $E = 83.7$ MeV; measured relative neutron yield $Y (0 °, E_{n})$ down to 4 MeV; calculated spectra at 83.7 and 53.8 MeV on basis of Serber model for deuteron stripping.

${}^{11}B (γ, π^{-}) {}^{11}C$ cross section near threshold

K. Min, P. Stoler, S. Trentalange, E. J. Winhold, P. F. Yergin, A. M. Bernstein, W. Turchinetz, and K. S. R. Sastry

Phys. Rev. C 14, 807 (1976) - Published 1 September, 1976

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Yields for the ${}^{11}B (γ, π^{-})$ reaction have been measured between its threshold at 142.0 MeV and 169 MeV by observing the residual ${}^{11}C$ activity. The reaction was initiated by thin-radiator bremsstrahlung. Measurements were made in 1 MeV steps up to 150 MeV, and in larger steps above this. The present results are consistent with previous data for this reaction obtained at higher energies. The cross section values near threshold deduced from the data are compared to recent preliminary theoretical values.

NUCLEAR REACTIONS ${}^{11}B (γ, π^{-})$ ; bremsstrahlung end-point energies to 169 MeV; measured yields by residual activity; deduced $σ (E_{γ})$ for $E_{γ} = E_{th}$ (142.0 MeV)-169 MeV.

( $α, {}^{8}{Be}$ ) reaction in the $1 p$ shell

G. J. Wozniak, D. P. Stahel, Joseph Cerny, and N. A. Jelley

Phys. Rev. C 14, 815 (1976) - Published 1 September, 1976

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A ${}^{8}{Be}$ identifier of high detection efficiency was utilized to investigate the ( $α, {}^{8}{Be}$ ) reaction on ${}^{16}O$ , ${}^{15}N$ , ${}^{14}N$ , ${}^{13}C$ , ${}^{12}C$ , ${}^{11}B$ , ${}^{10}B$ , and ${}^{9}{Be}$ targets at bombarding energies between 65 and 72.5 MeV. Differential cross sections were measured from $θ_{c . m .} = 20 ° - 70 °$ for solid targets and over a more restricted range for the nitrogen gas targets. Excitation functions were obtained over a larger energy range for the ${}^{12}C$ and ${}^{16}O$ targets. At these energies, the ( $α, {}^{8}{Be}$ ) reaction was found to proceed predominantly via a direct $α$ -cluster pickup mechanism and to populate strongly only those levels consistent with this mechanism. The data were analyzed in the framework of the exact finite-range distorted-wave Born approximation. Absolute and relative $α$ -particle spectroscopic factors were extracted for 22 states. Good agreement was found between these experimental values and the theoretical predictions of Kurath and of Rotter for the extent of α clustering in these light nuclei.

NUCLEAR REACTIONS ${}^{16}O$ , ${}^{15}N$ , ${}^{14}N$ , ${}^{13}C$ , ${}^{12}C$ , ${}^{11}B$ , ${}^{10}B$ , ${}^{9}{Be} (α, {}^{8}{Be})$ $E_{α} = 65 - 72.5$ MeV; measured $σ (E_{f}, θ)$ ; energy levels ${}^{12}C$ , ${}^{11}B$ , ${}^{10}B$ , ${}^{9}{Be}$ , ${}^{8}{Be}$ , ${}^{7}{Li}$ , ${}^{6}{Li}$ , ${}^{5}{He}$ ; resolution 450 keV; DWBA analysis, deduced $S_{α}$ for 22 states, comparisons with theoretical $S_{α}$ .

Measurement of the static quadrupole moments of the first $2^{+}$ states in ${}^{94}{Mo}$ , ${}^{96}{Mo}$ , ${}^{98}{Mo}$ , and ${}^{100}{Mo}$

P. Paradis, G. Lamoureux, R. Lecomte, and S. Monaro

Phys. Rev. C 14, 835 (1976) - Published 1 September, 1976

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The static quadrupole moments $Q_{2^{+}}$ and the $B (E 2; 0^{+} \to 2^{+})$ values of the first $2^{+}$ excited states in ${}^{94}{Mo}$ , ${}^{96}{Mo}$ , ${}^{98}{Mo}$ , and ${}^{100}{Mo}$ have been determined by Coulomb excitation experiments performed by resolving elastically and inelastically backward scattered ${}^{4}{He}$ and ${}^{16}O$ projectiles detected in four surface barrier detectors. The measurements yielded for $Q_{2^{+}}$ and $B (E 2; 0^{+} \to 2^{+}) : (- 0.13 \pm 0.08)$ e b or (+0.01 ± 0.08) e b and (0.196 ± 0.003) $e^{2}$ $b^{2}$ for ${}^{94}{Mo}$ ; (-0.20 ± 0.08) e b or (+0.04 ± 0.08) e b and (0.270 ± 0.004) $e^{2}$ $b^{2}$ for ${}^{96}{Mo}$ ; (-0.20 ± 0.09) e b or (+0.16 ± 0.09) e b and (0.266 ± 0.005) $e^{2}$ $b^{2}$ for ${}^{98}{Mo}$ ; (-0.42 ± 0.09) e b or (-0.10 ± 0.09) e b and (0.511 ± 0.009) $e^{2}$ $b^{2}$ for ${}^{100}{Mo}$ .

NUCLEAR REACTIONS ${}^{94, 96, 98, 100}{Mo} (α, α^{'})$ , $E = 8.0$ MeV; ${}^{94, 96, 98, 100}{Mo}$ ( ${}^{16}O$ , ${}^{16}{O'}$ ), $E = 36.0 or 36.5$ MeV; measured $σ {(E, E_{{}^{16}O^{'}})}_{\circ} {}^{94, 96, 98, 100}{Mo}$ deduced $Q_{2^{+}}$ , $B (E 2; 0^{+} \to 2^{+})$ . Enriched targets.

Unbound isobaric analog states in ${}^{53}{Mn}$ : The reactions ${}^{52}{Cr} ({}^{3}{He}, d) {}^{53}{Mn}$ and ${}^{52}{Cr} ({}^{3}{He}, d p) {}^{52}{Cr}$

S. Galès, S. Fortier, H. Laurent, J. M. Maison, and J. P. Schapira

Phys. Rev. C 14, 842 (1976) - Published 1 September, 1976

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The ${}^{52}{Cr} ({}^{3}{He}, d) {}^{53}{Mn}$ reaction investigated at 25 MeV incident energy with a split pole spectrometer was used to populate highly excited analog states in ${}^{53}{Mn}$ . Fifty-two levels between 6.9 and 12.0 MeV excitation energy were observed in ${}^{53}{Mn}$ . The main components of the $T_{>} 2 p_{\frac{3}{2}}$ , $2 p_{\frac{1}{2}}$ , $1 f_{\frac{5}{2}}$ , and $1 g_{\frac{9}{2}}$ single-particle strengths were identified. Angular distributions of transitions to 38 unbound-levels in ${}^{53}{Mn}$ have been extracted and analyzed with distorted-wave Born approximation and Gamov functions (as form factors for the transferred proton) to yield the absolute spectroscopic strength. An appreciable amount of the missing $2 p_{\frac{3}{2}}$ , $2 p_{\frac{1}{2}}$ , and $1 f_{\frac{5}{2}}$ proton $T_{<}$ strengths is observed in ${}^{53}{Mn}$ between 7.0 and 8.5 MeV whereas a small fraction of the $1 g_{\frac{9}{2}}$ and $2 d_{\frac{5}{2}}$ single-particle orbitals appears between 7.0 and 12 MeV excitation energy. The ${}^{52}{Cr} ({}^{3}{He}, d p) {}^{52}{Cr}$ reaction was performed at 24 MeV incident energy using a triplet of magnetic quadrupole lenses. The angular correlations of the emitted protons were measured in coincidence using method II of Litherland and Ferguson with zero degree detection of deuteron groups. Spins, population parameters, and branching ratios of proton partial widths to the ground and excited states of the target were determined for 14 unbound levels in ${}^{53}{Mn}$ from the analysis of the angular correlation data. These two experiments provide a rather complete description of the spectroscopic properties of the analog of the levels of ${}^{53}{Cr}$ up to 5.0 MeV excitation energy. A comparison is made with the previous ( ${}^{3}{He}, d$ ), ( $p, γ$ ), ( $p, p$ ), and ( $d, p$ ) results on the same target. Components of the ${}^{53}{Cr}$ parent states which consist of a neutron coupled to an excited state of the ${}^{52}{Cr}$ nucleus are also determined.

NUCLEAR REACTIONS ${}^{52}{Cr} ({}^{3}{He}, d)$ , $E = 25$ MeV; measured $σ (E_{d}, θ)$ , ${}^{52}{Cr} ({}^{3}{He}, d p)$ , $E = 24$ MeV; measured $σ (E_{d}, E_{p}, θ_{p})$ . ${}^{53}{Mn}$ deduced IAS, $L$ , $J$ , $π$ , $S$ , $Γ_{p}$ , proton branching. ${}^{53}{Cr}$ , ${}^{53}{Mn}$ analog pairs deduced Coulomb displacement energies. DWBA analysis using Gamov functions as form factors. Natural targets.

Mean lifetimes of the ${}^{44}{Sc}$ 1648, 1652, 1681, and 1768 keV levels

J. P. Coffin, F. Jundt, A. Gallmann, and E. K. Warburton

Phys. Rev. C 14, 861 (1976) - Published 1 September, 1976

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The lifetimes of four ${}^{44}{Sc}$ levels in the range of excitation energy 1.6-1.8 MeV have been measured by the Doppler shift attenuation method as follows [ $E_{x}$ (in keV); $τ$ (in fs)]: (1648.28 ± 0.5; 180 ± 28), (1651.63 ± 0.5; 155 ± 35), (1680.6 ± 0.5; 140 ± 33), (1767.6 ± 0.5; 80 ± 17). The $γ$ decays of the 1648- and 1652-keV levels had not been previously reported. More definitive branching ratios must be obtained for these levels before the nuclear structure information inherent in these measurements can be utilized.

NUCLEAR REACTIONS ${}^{41}K (α, n)$ $E = 5 - 11$ MeV; measured $n γ$ , $γ γ$ coincidences, and $E_{γ}$ ; deduced levels in ${}^{44}{Sc}$ ; measured $γ$ -ray Doppler shifts; deduced $T_{\frac{1}{2}}$ enriched target, Ge(Li) detectors.

Excitation of three isospin modes of the giant magnetic dipole resonance in mass 24 isobars

R. J. Peterson, F. E. Cecil, R. A. Ristinen, E. R. Flynn, Nelson Stein, and J. D. Sherman

Phys. Rev. C 14, 868 (1976) - Published 1 September, 1976

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All three isospin modes of two $T = 1, 1^{+}$ states in mass 24 have been studied by ( ${}^{3}{He}, t$ ), ( ${}^{3}{He}$ , ${}^{3}{He'}$ ), and ( $t, {}^{3}{He}$ ) reactions on ${}^{24}{Mg}$ . The relative strengths of the two $1^{+}$ states in each reaction agree with the relative strengths of the electromagnetic transitions, but the shapes and magnitudes of the charge-exchange data are not as predicted by a one-step interaction with a central force. It is necessary to perform a two-step coupled-channel Born-approximation calculation via intermediate ${}^{4}{He}$ channels using mixed wave functions to account for the results.

NUCLEAR REACTIONS ${}^{24}{Mg} ({}^{3}{He}, t)$ , ( $t, {}^{3}{He}$ ), ( ${}^{3}{He}$ , ${}^{3}{He'}$ ) to $1^{+}$ states. Members of isospin multiplet. Giant $M 1$ states. DWBA, CCBA analysis.

Quasielastic ( $p, n$ ) reactions induced by polarized protons

J. Gosset, B. Mayer, and J. L. Escudié

Phys. Rev. C 14, 878 (1976) - Published 1 September, 1976

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The differential analyzing power has been measured in the quasielastic ( $p, n$ ) reaction on ${}^{49}{Ti}$ , ${}^{56}{Fe}$ , ${}^{64}{Ni}$ , ${}^{70}{Zn}$ , ${}^{90}{Zr}$ , ${}^{96}{Zr}$ , ${}^{117}{Sn}$ , ${}^{165}{Ho}$ , and ${}^{208}{Pb}$ at 22.8 MeV. Fits to the experimental data in a macroscopic Lane-model analysis were improved by adding a spin-orbit term $V_{so}^{(1)}$ in the isospin-dependent part of the optical potential. The sign of $V_{so}^{(1)}$ agrees with that given by a simple model and its value does not depend very much on the target nucleus. However, the average value of $V_{so}^{(1)}$ depends on the geometry used for the spin-orbit optical potential, an ambiguity which corresponds to a nearly constant product of the depth and of the diffuseness. A microscopic distorted-wave Born-approximation analysis was made, but due to several ambiguities in the calculation, it has not been possible to determine the isovector spin-orbit part $v_{LS τ}$ of the nucleon-nucleon effective interaction.

NUCLEAR REACTIONS Quasielastic ( $\vec{p}, n$ ) reactions on ${}^{49}{Ti}$ , ${}^{56}{Fe}$ , ${}^{64}{Ni}$ , ${}^{70}{Zn}$ , ${}^{90}{Zr}$ , ${}^{96}{Zr}$ , ${}^{117}{Sn}$ , ${}^{165}{Ho}$ , and ${}^{208}{Pb}$ ; $E = 22.8$ MeV; measured differential analyzing power $A (θ)$ macroscopic Lane-model analysis with an isospin-dependent spin-orbit term in the optical potential; microscopic DWBA analysis.

Neutron pickup by alpha particles to unbound states

D. R. Brown, I. Halpern, J. R. Calarco, P. A. Russo, D. L. Hendrie, and H. Homeyer

Phys. Rev. C 14, 896 (1976) - Published 1 September, 1976

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Two conspicuous peaks are observed in the two-dimensional coincidence spectra of $α$ particles and neutrons emitted in bombardments of ${}^{12}C$ , Rh, ${}^{208}{Pb}$ , and U with 90 MeV $α$ particles. Through their energy-angle correlation these peaks are identified as arising from the breakup products of ${}^{5}{He}$ (g.s.) formed in the ( $α, {}^{5}{He} (g . s .)$ ) reaction. A somewhat less prominent peaking of events is identified as the signature for the breakup of ${}^{6}{H e *}$ (1.8 MeV) formed by two-neutron pickup. A distorted-wave Born-approximation calculation was carried out for the ( $α, {}^{5}{He} (g . s .)$ ) reaction on ${}^{208}{Pb}$ and was found to fit the measurements. The large differential cross section for the ( $α, {}^{5}{He} (g . s .)$ ) reaction confirms an earlier interpretation of the somewhat square structure observed in the spectra of inelastically scattered $α$ particles.

NUCLEAR REACTIONS ${}^{208}{Pb}$ , Rh, ${}^{12}C$ , ${}^{nat}U (α, {}^{5}{He})$ ( $α$ , ${}^{6}{He}$ (1.8 MeV)), $E = 42, 90$ MeV, measured two-dim $α - n$ coin. Spectra, deduced $σ (θ)$ for ${}^{208}{Pb} (α, {}^{5}{He})$ , compared DWBA.

Spin and parity assignments in ${}^{38}K$ via the ( $\vec{d}, α$ ) reaction near 0°

D. T. Petty, P. G. Ikossi, J. A. Kuehner, and J. Szücs

Phys. Rev. C 14, 908 (1976) - Published 1 September, 1976

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The tensor analyzing power, $T_{20}$ , is measured at $θ = 3 °$ in the ${}^{40}{Ca} (\vec{d}, α) {}^{38}K$ reaction at beam energies of 7.5, 7.75, and 8.0 MeV. Assignments of a natural or unnatural parity are made for states in ${}^{38}K$ from 1698 to 3978 keV and in several cases, spin and/or parity assignments are deduced. In particular assignments of $3^{-}$ , ${(2, 4)}^{-}$ , $2^{-}$ , ( $2^{-}$ , $3^{+}$ ), $2^{-}$ , $1^{+}$ , and $1^{+}$ are made to the 2613, 2647, 2870, 3317, 3815, 3857, and 3978 keV states, respectively.

NUCLEAR REACTIONS ${}^{40}{Ca} (\vec{d}, α)$ , $E = 7.5, 7.75, 8.0$ MeV; measured $T_{20} (0 °)$ , deduced $J$ , $π$ .

States in ${}^{243}{Pu}$ from the ( $n, γ$ ), ( $d, p$ ), and ( $d, t$ ) reactions

R. F. Casten, W. R. Kane, J. R. Erskine, A. M. Friedman, and D. S. Gale

Phys. Rev. C 14, 912 (1976) - Published 1 September, 1976

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The levels of ${}^{243}{Pu}$ have been studied with the ${}^{242}{Pu} (n, γ) {}^{243}{Pu}$ , ${}^{242}{Pu} (d, p) {}^{243}{Pu}$ , and ${}^{244}{Pu} (d, t) {}^{243}{Pu}$ reactions. Nearly all levels detected below 1100 keV have been assigned to rotational bands built upon Nilsson orbitals by considering the expected rotational spacings, the ( $d, p$ ) and ( $d, t$ ) cross sections which are characteristic of the specific orbital, the spin-parity information deduced from the ( $n, γ$ ) data, and the systematics of nearby nuclei. In all, 12 rotational bands were identified. In addition a likely octupole excitation was located at 704 keV. Of particular interest is the fact that the ${1 / 2}^{-}$ [501] orbital is not significantly fragmented in ${}^{243}{Pu}$ . Nilsson model and Coriolis calculations are performed and the predictions for $γ$ -ray transition rates are compared to the empirical results. In general good agreement is found, but with a few noted exceptions.

NUCLEAR REACTIONS ${}^{242}{Pu} (n, γ)$ , $E = 2.96$ eV; measured $E_{γ}$ , $I_{γ}$ , $γ - γ$ coin. ${}^{243}{Pu}$ deduced levels, $J$ , $π$ , Ge(Li) detector. ${}^{242}{Pu} (d, p)$ , ${}^{244}{Pu} (d, t)$ , $E = 12$ MeV; measured $Q_{0}$ , $E_{x}$ , and $σ (θ)$ . ${}^{243}{Pu}$ deduced levels, $l$ . Enriched targets. ${}^{243}{Pu}$ deduced levels, $J$ , $π$ , Nilsson assignments, rotational bands from combined experiments. Calculated $γ$ -ray transition probabilities with Nilsson model and Coriolis interaction.

Isospin and strong coupling effects in neutron scattering from even- $A$ Se isotopes

J. Lachkar, M. T. McEllistrem, G. Haouat, Y. Patin, J. Sigaud, and F. Coçu

Phys. Rev. C 14, 933 (1976) - Published 1 September, 1976

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Differential cross sections for elastic scattering from the even- $A$ isotopes of Se have been measured at 6, 8, and 10 MeV. Inelastic scattering differential cross sections have been obtained at 6- and 8-MeV incident energies. The results have been analyzed in a coupled channel model to determine the isospin coefficients in the real and imaginary parts of the scattering potential and the deformation parameters $β_{2}$ appropriate to neutron scattering in these vibrational nuclei. Both the coupling to the first $2^{+}$ level and the imaginary scattering potential vary strongly between ${}^{76}{Se}$ and ${}^{82}{Se}$ , and in such a way that their effects cancel each other for inelastic scattering. It is shown that with an adequate data set the strong coupling and isospin dependencies of neutron scattering can be separated. The normalization uncertainty of these measurements is about 7%, and the statistical precision ranges from 1 to 10%.

NUCLEAR REACTIONS ${}^{76}{Se}$ , ${}^{82}{Se} (n, n)$ and ( $n, n^{'}$ ), $E_{n} = 6 - 8 and 10$ MeV, ${}^{78}{Se}$ , ${}^{80}{Se} (n, n)$ , and ( $n, n^{'}$ ), $E_{n} = 8$ MeV. Measured ( $E_{n}, θ$ ). Enriched targets. Coupled channel analysis.

Positive-parity levels in ${}^{41}{Ca}$ populated in the ${}^{40}{Ca} (\vec{d}, p) {}^{41}{Ca} (J^{+})$ reaction

R. N. Boyd, D. Elmore, H. Clement, W. P. Alford, J. A. Kuehner, and G. D. Jones

Phys. Rev. C 14, 946 (1976) - Published 1 September, 1976

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Differential cross sections and vector analyzing powers for the ${}^{40}{Ca} (\vec{d}, p)$ reaction are presented as a test of the particle-core coupling model for high-spin positive parity levels at 2.88, 3.20, 3.37, and 3.83 MeV in ${}^{41}{Ca}$ . The data representations by the coupled-channels Born approximation support the model. In contrast, the distorted-wave Born approximation fails completely to represent the analyzing power data for some levels.

NUCLEAR REACTIONS ${}^{40}{Ca} (\vec{d}, p)$ , $E = 11.0$ MeV; measured $σ (θ)$ , $A (θ)$ . ${}^{41}{Ca}$ positive-parity levels deduced structure. CCBA analysis, resolution 15 keV, $θ = 10 ° to 130 °$ for $σ (θ)$ , 10° to 90° for $A (θ)$ , $Δ θ = 10 °$ .

Electron scattering from vibrational nuclei

J. W. Lightbody, Jr., S. Penner, S. P. Fivozinsky, P. L. Hallowell, and Hall Crannell

Phys. Rev. C 14, 952 (1976) - Published 1 September, 1976

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We present electron scattering form factors for the ground states and several low energy quadrupole excitations of the nuclei ${}^{52}{Cr}$ , ${}^{110}{Pd}$ , ${}^{114}{Cd}$ , and ${}^{116}{Sn}$ . For ${}^{116}{Sn}$ we also present the form factor for the lowest octupole excitation. From these data we derive ground state charge distribution parameters as well as $B (EL)$ values. We attempt to interpret the observed $2^{+}$ states as the one- and two-phonon states of an anharmonic vibrational model. Predictions are made for the electromagnetic decay branching ratios and excited state electric quadrupole moments.

NUCLEAR REACTIONS $e + {}^{52}{Cr}$ , ${}^{110}{Pd}$ , ${}^{114}{Cd}$ , ${}^{116}{Sn}$ ; $θ = 127.5 °$ , $E = 40, 50, 60, 75, 92, 110$ MeV; ground state charge distribution parameters; anharmonic vibrator model fits to quadrupole excitation data.

Spin-state determinations and spacings of neutron resonances for ${}^{187}{Os}$ and ${}^{189}{Os}$

A. Stolovy, A. I. Namenson, and B. L. Berman

Phys. Rev. C 14, 965 (1976) - Published 1 September, 1976

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The spin states of 25 resonances for ( ${}^{187}{Os} + n$ ) and 40 resonances for ( ${}^{189}{Os} + n$ ) have been determined with probabilities of correctness greater than 80%. Spin assignments were made on the basis of the ratios of low-energy $γ$ -ray intensities associated with neutron capture in the resonances. For both nuclei, the spin distributions are consistent with a ( $2 J + 1$ ) level-density distribution. The level spacings favor the theory of Dyson and Mehta, but an uncorrelated Wigner distribution cannot be ruled out definitely. These results provide important input parameters for the astrophysical determination of the age of the universe by the ${}^{187}{Re}$ → ${}^{187}{Os}$ nuclear dating technique.

NUCLEAR REACTIONS ${}^{187, 189}{Os} (n, γ)$ , $E = 5 - 350$ eV, enriched targets; measured $E_{n}$ , $E_{γ}$ , $I_{γ}$ ; deduced $J$ , $Δ_{3}$ , $〈 D 〉$ .

Possible evidence for exchange effects in the ${}^{16}O ({}^{6}{Li}, α) {}^{18}F$ reaction at $E_{{}^{6}{Li}} = 34$ MeV

G. E. Moore and K. W. Kemper

Phys. Rev. C 14, 977 (1976) - Published 1 September, 1976

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Fifty-four-point angular distributions in the angular range 2.5° to 170° have been measured for the ${}^{16}O ({}^{6}{Li}, α) {}^{18}F$ reaction to the $1^{+}$ (0.0 MeV), $3^{+}$ (0.937 MeV), and $0^{-}$ + $5^{+}$ (1.1 MeV) states in ${}^{18}F$ at a bombarding energy of 34 MeV. In addition, forward angle data have been measured for the $2^{-}$ (2.101 MeV), $1^{+}$ (3.725 MeV), $3^{-}$ (3.791 MeV), and $2^{+}$ (3.836 MeV) states. The angular distributions for all of the above states are forward peaked and have little structure at back angles. The general structure of the first 60° of the angular distributions can be reproduced by zero-range two-particle transfer distorted-wave Born-approximation calculations; however, the calculations are generally 3° and as much as 10° out of phase with the data past the first maximum. A zero-range distorted-wave Born-approximation normalization factor of 100 is obtained assuming the $5^{+}$ state to be a pure ${(d_{\frac{5}{2}})}^{2}$ configuration. Finite-range distorted-wave Born-approximation calculations which include the $2 S$ and $1 D$ components of ${}^{6}{Li}$ do not improve the fits to the data and are similar to zero-range calculations at forward angles. The $1 D$ component was shown to have little effect on the calculated angular distributions. The absolute magnitudes of the cross sections are predicted to within a factor of 2 when the ${}^{18}F$ shell model wave functions of Kuo and Brown are used in the finite-range distorted-wave Born-approximation calculations. Two-particle and cluster form factors used in the finite-range calculations gave equivalent fits to the data. The magnitude of the cross section at angles greater than 90° and the phase of the forward angle data could not be reproduced by any of the calculations. The failure of the distorted-wave Born-approximation calculations at back angles suggests that a more complete description of the reaction mechanism which includes the exchange of an $α$ particle in ${}^{16}O$ with the ${}^{6}{Li}$ projectile is necessary.

NUCLEAR REACTIONS ${}^{16}O ({}^{6}{Li}, α) {}^{18}F$ , $E = 34$ MeV; measured $σ (θ) θ = 2.5 ° - 170 °$ lab, $Δ θ = 2.5 °$ ; compared data to zero-range and finite-range DWBA calculations using shell model wave functions. Extracted ( ${}^{6}{Li}, α$ ) zero-range normalization factor.

Coulomb-nuclear interference effects in inelastic scattering of ${}^{16}O$ from ${}^{24}{Mg}$

J. X. Saladin, I. Y. Lee, R. C. Haight, and D. Vitoux

Phys. Rev. C 14, 992 (1976) - Published 1 September, 1976

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Decay schemes for high-spin states in ${}^{35, 36, 37}{Cl}$ and ${}^{37}{Ar}$ from heavy-ion fusion-evaporation reactions

E. K. Warburton, J. W. Olness, A. R. Poletti, and J. J. Kolata

Phys. Rev. C 14, 996 (1976) - Published 1 September, 1976

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The $γ$ -ray decays of high-spin states in ${}^{35, 36, 37}{Cl}$ and ${}^{37}{Ar}$ were studied via heavy-ion-induced reactions involving ${}^{14}N$ and ${}^{18}O$ bombardment of targets of ${}^{24, 26}{Mg}$ and ${}^{27}{Al}$ . Decay schemes and spin-parity assignments were deduced from $γ γ$ -coincidence measurements, $γ$ -ray angular distribution and linear polarization measurements, and recoil-distance lifetime measurements. The observed levels are compared to predictions of the weak-coupling model. It is concluded that all the observed high-spin states can be assigned to configurations based on one- or two-nucleon excitations from the ( $2 s, 1 d$ ) shell into the ( $1 f, 1 p$ ) shell, and that not all the energetically available yrast levels of these configurations have, as yet, been found.

NUCLEAR REACTIONS (HI, $xn$ , $yp$ , $z α$ ) studies for ${}^{35, 36, 37}{Cl}$ and ${}^{37}{Ar}$ , with ${}^{14}N$ , ${}^{18}O$ projectiles, ${}^{24, 26}{Mg}$ and ${}^{27}{Al}$ targets, $E = 20 - 60$ MeV; measured $γ γ$ coin.; deduced levels; measured $σ (E_{γ}, θ)$ and $P_{γ}$ ; deduced $J^{π}$ for high-spin levels; measured recoil distance; deduced $τ$ . Natural and isotopically enriched targets, Ge(Li) detectors. Compared results to weak-coupling model predictions.

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Theory and experiment for the reaction ${}^{6}{Li} (e, d) e^{'}$ , ${}^{4}{He}$

Soft photon nucleon-nucleon bremsstrahlung in the potential model

Neutron spectrum at 0° from 83.7 MeV deuterons on beryllium

${}^{11}B (γ, π^{-}) {}^{11}C$ cross section near threshold

( $α, {}^{8}{Be}$ ) reaction in the $1 p$ shell

Measurement of the static quadrupole moments of the first $2^{+}$ states in ${}^{94}{Mo}$ , ${}^{96}{Mo}$ , ${}^{98}{Mo}$ , and ${}^{100}{Mo}$

Unbound isobaric analog states in ${}^{53}{Mn}$ : The reactions ${}^{52}{Cr} ({}^{3}{He}, d) {}^{53}{Mn}$ and ${}^{52}{Cr} ({}^{3}{He}, d p) {}^{52}{Cr}$

Mean lifetimes of the ${}^{44}{Sc}$ 1648, 1652, 1681, and 1768 keV levels

Excitation of three isospin modes of the giant magnetic dipole resonance in mass 24 isobars

Quasielastic ( $p, n$ ) reactions induced by polarized protons

Neutron pickup by alpha particles to unbound states

Spin and parity assignments in ${}^{38}K$ via the ( $\vec{d}, α$ ) reaction near 0°

States in ${}^{243}{Pu}$ from the ( $n, γ$ ), ( $d, p$ ), and ( $d, t$ ) reactions

Isospin and strong coupling effects in neutron scattering from even- $A$ Se isotopes

Positive-parity levels in ${}^{41}{Ca}$ populated in the ${}^{40}{Ca} (\vec{d}, p) {}^{41}{Ca} (J^{+})$ reaction

Electron scattering from vibrational nuclei

Spin-state determinations and spacings of neutron resonances for ${}^{187}{Os}$ and ${}^{189}{Os}$

Possible evidence for exchange effects in the ${}^{16}O ({}^{6}{Li}, α) {}^{18}F$ reaction at $E_{{}^{6}{Li}} = 34$ MeV

Coulomb-nuclear interference effects in inelastic scattering of ${}^{16}O$ from ${}^{24}{Mg}$

Decay schemes for high-spin states in ${}^{35, 36, 37}{Cl}$ and ${}^{37}{Ar}$ from heavy-ion fusion-evaporation reactions

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