Recent Articles

Level structure of ${}^{173}{Yb}$ via the ( $d, p$ ) and ( $d, t$ ) reactions

R. W. Tarara, J. D. Goss, and C. P. Browne

Phys. Rev. C 16, 2167 (1977) - Published 1 December, 1977

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We have studied the level structure of ${}^{173}{Yb}$ via the ${}^{172}{Yb} (d, p) {}^{173}{Yb}$ and ${}^{174}{Yb} (d, t) {}^{173}{Yb}$ reactions. We measured the excitation energies of 96 states up to 2.63 MeV, including all but two of the adopted levels. 55 of the states were not previously reported. We took angular distributions on each reaction and analyzed them with distorted-wave Born-approximation theory. Our $l$ -value determinations support all previous assignments with the exception of the tentative ${9 / 2}^{-}$ assignment of the 1606-keV state which favors an $l = 2$ fit to the data. We can assign the 1867-keV state as $l = 3, and 16$ other states can be given probable $l$ values or limited to two or three possible $l' s$ . We can make several tentative placements of levels within the proposed band structure of ${}^{173}{Yb}$ through the use of the standard band formula, our preferred $l$ -value fits, and our excitation energy determinations.

NUCLEAR REACTIONS ${}^{172}{Yb} (d, p)$ , ${}^{174}{Yb} (d, t)$ , ${}^{173}{Yb} (d, d^{'})$ , $E (d) = 14$ MeV; measured excitation energies, $σ (p, θ)$ , $σ (t, θ)$ , $θ = 16 - 120 °$ ; ${}^{173}{Yb}$ deduced $l$ , $J$ , $π$ , $S$ ; enriched targets, DWBA analysis, magnetic spectrograph.

Energy dependence of the ${}^{119}{Sn} (p, n) {}^{119}{Sn}$ (IAS) reaction

D. H. Fitzgerald, G. W. Greenlees, J. S. Lilley, C. H. Poppe, S. M. Grimes, and C. Wong

Phys. Rev. C 16, 2181 (1977) - Published 1 December, 1977

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Angular distributions for the ${}^{119}{Sn} (p, n) {}^{119}{Sb}$ (isobaric analog state) charge-exchange reaction have been measured at several energies between 16 and 20 MeV using both a neutron-proton coincidence method and a conventional pulsed beam time-of-flight method. The results furnish a value for the relative proton decay width of the analog of the ${}^{119}{Sn}$ ground state: $Γ_{p} | Γ = 0.320 \pm 0.015$ . The data exhibit the well-known "resonancelike" behavior a few MeV above threshold. Nevertheless, excellent fits to both the magnitude and shape of $σ (θ)$ are obtained with a Lane-model-consistent optical potential, provided that the strength of the neutron absorption potential decreases smoothly in a realistic way with decreasing neutron energy. This modified neutron potential also gives improved fits to low-energy neutron elastic scattering and reaction cross section data.

NUCLEAR REACTIONS ${}^{119}{Sn} (p, n) {}^{119}{Sb}$ (IAS), $E_{p} = 16, 17, 18, 19, 20$ MeV; measured $σ (E_{p}, θ)$ ; deduced $Γ_{p} | Γ$ , isospin form factor, energy dependence of neutron imaginary potential.

( $d, p$ ) reactions on ${}^{124}{Sn}$ , ${}^{130}{Te}$ , ${}^{138}{Ba}$ , ${}^{140}{Ce}$ , ${}^{142}{Nd}$ , and ${}^{208}{Pb}$ below and near the Coulomb barrier

A. Strömich, B. Steinmetz, R. Bangert, B. Gonsior, M. Roth, and P. von Brentano

Phys. Rev. C 16, 2193 (1977) - Published 1 December, 1977

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The reactions ${}^{124}{Sn} (d, p) {}^{125}{Sn}$ , ${}^{130}{Te} (d, p) {}^{131}{Te}$ , ${}^{138}{Ba} (d, p) {}^{139}{Ba}$ , ${}^{140}{Ce} (d, p) {}^{141}{Ce}$ , ${}^{142}{Nd} (d, p) {}^{143}{Nd}$ , and ${}^{208}{Pb} (d, p) {}^{209}{Pb}$ have been investigated by measuring the differential cross sections of the ( $d, p$ ) reactions and of the elastic scattering of deuterons at various incident energies below and near the Coulomb barrier. Using scattering potentials which describe the elastic scattering of the particles in the entrance and exit channels, reduced normalizations of 40 final states have been determined which are nearly independent of the uncertainties due to the ambiguities of optical potentials. The experimental errors are 8% on the average. In the energy region studied the expected constancy of derived spectroscopic factors is demonstrated.

NUCLEAR REACTIONS ${}^{124}{Sn}$ , ${}^{130}{Te}$ , ${}^{138}{Ba}$ , ${}^{140}{Ce}$ , ${}^{142}{Nd}$ , ${}^{208}{Pb} (d, p)$ , ( $d, d$ ), $5.0 MeV \leq E_{d} \leq 11.0 MeV$ , measured $\frac{d σ}{d Ω (E_{d}, θ)}$ , enriched targets, deduced scattering potentials, reduced normalizations of 40 final states with experimental errors of 8% on the average, spectroscopic factors.

$E 2$ and $E 4$ reduced matrix elements of ${}^{154, 156, 158, 160}{Gd}$ and ${}^{176, 178, 180}{Hf}$

R. M. Ronningen, J. H. Hamilton, L. Varnell, J. Lange, A. V. Ramayya, G. Garcia-Bermudez, W. Lourens, L. L. Riedinger, F. K. McGowan, P. H. Stelson, R. L. Robinson, and J. L. C. Ford, Jr.

Phys. Rev. C 16, 2208 (1977) - Published 1 December, 1977

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Coulomb excitation by ${}^{4}{He}$ ions was studied to deduce the electric quadrupole and hexadecapole reduced transition matrix elements of deformed gadolinium and hafnium nuclei. Our values of $〈 0^{+} ∥ M (E 2) ∥ 2^{+} 〉$ for ${}^{154, 156, 158, 160}{Gd}$ are 1.962(20), 2.136(7), 2.230(12), and 2.269(14) eb. For ${}^{176, 178, 180}{Hf}$ they are 2.281, 2.204, and 2.176 eb. The values of $〈 0^{+} ∥ M (E 4) ∥ 4^{+} 〉$ for ${}^{156, 158, 160}{Gd}$ are 0.42 ± 0.08, ${0.34}^{+ 0.20}_{- 0.22}$ , and ${0.35}^{+ 0.09}_{- 0.07}$ e $b^{2}$ . For ${}^{176, 178, 180}{Hf}$ they are 0.26 ± 0.12, ${0.23}^{+ 0.11}_{- 0.20}$ , and ${0.21}^{+ 0.11}_{- 0.16}$ e $b^{2}$ , if positive values are taken, and -0.76 ± 0.15, -0.67 ± 0.20, and -0.65 ± 0.16 e $b^{2}$ if they are negative. We compare our measurements with other experimental values and with theoretical predictions of quadrupole and hexadecapole moments.

NUCLEAR REACTIONS ${}^{154, 156, 158, 160}{Gd} (α, α^{'})$ , ${}^{176, 178, 180}{Hf} (α, α^{'})$ $E_{α} = 11.5 - 14$ MeV; measured Coulomb excitation cross sections at $θ_{lab} = 150 °$ ; deduced $〈 0^{+} ∥ M (E 2) ∥ 2^{+} 〉$ , $〈 0^{+} ∥ M (E 4) ∥ 4^{+} 〉$ using rotational model; extracted model-dependent charge deformation parameters $β_{2}^{c}$ , $β_{4}^{c}$ .

Coulomb excitation measurements of reduced $E 2$ and $E 4$ transition matrix elements in ${}^{156, 158}{Dy}$ , ${}^{162, 164}{Er}$ , and ${}^{168}{Yb}$

R. M. Ronningen, R. B. Piercey, J. H. Hamilton, C. F. Maguire, A. V. Ramayya, H. Kawakami, B. van Nooijen, R. S. Grantham, W. K. Dagenhart, and L. L. Riedinger

Phys. Rev. C 16, 2218 (1977) - Published 1 December, 1977

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The reduced $E 2$ and $E 4$ transition matrix elements were measured for ${}^{156, 158}{Dy}$ , ${}^{162, 164}{Er}$ , and ${}^{168}{Yb}$ via Coulomb excitation with $α$ particles at energies below those where nuclear effects are expected to contribute significantly. Charge deformation parameters $β_{2}^{c}$ and $β_{4}^{c}$ were extracted from these matrix elements by assuming the charge distribution to have a deformed Fermi distribution form with quadrupole and hexadecapole components. Values of $〈 0^{+} ∥ (E 2) ∥ 2^{+} 〉$ of 1.929, 2.161, 2.238, 2.341, and 2.402 eb were found for ${}^{156, 158}{Dy}$ , ${}^{162, 164}{Er}$ , and ${}^{168}{Yb}$ , respectively, with ≲1% uncertainty. The values of $〈 0^{+} ∥ M (E 4) ∥ 4^{+} 〉$ for these same respective nuclei are ${0.21}_{- 0.20}^{+ 0.16}$ , ${0.16}_{- 0.15}^{+ 0.10}$ , ${0.16}_{- 0.26}^{+ 0.14}$ , ${0.12}_{- 0.13}^{+ 0.12}$ , and ${0.19}_{- 0.19}^{+ 0.14}$ ${e b}^{2}$ .

NUCLEAR REACTIONS ${}^{156, 159}{Dy} (α, α^{'})$ , ${}^{162, 164}{Er} (α, α^{'})$ , ${}^{168}{Yb} (α, α^{'})$ , $E_{α} = 12 - 13$ MeV; measured Coulomb excitation cross sections relative to elastic cross sections at $θ_{lab} = 150 °$ ; deduced $〈 0^{+} ∥ M (E 2) ∥ 2^{+} 〉$ , $〈 0^{+} ∥ M (E 4) ∥ 4^{+} 〉$ , using rotational model; extracted charges deformation parameters $β_{2}^{c}$ , $β_{4}^{c}$ from rotational model and Fermi charge distribution. Enriched targets.

Strong collective excitations in low energy neutron scattering from transitional nuclei

D. F. Coope, S. N. Tripathi, M. C. Schell, J. L. Weil, and M. T. McEllistrem

Phys. Rev. C 16, 2223 (1977) - Published 1 December, 1977

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Elastic and inelastic scattering cross sections for 2.47 MeV neutrons bombarding ${}^{148, 150, 152}{Sm}$ nuclei were measured. The effects of the stable nuclear deformation on the scattering are unexpectedly pronounced. The inelastic scattering cross sections to the $2^{+}$ , $4^{+}$ , and $6^{+}$ rotational levels of ${}^{152}{Sm}$ are anomalously large, and there is evidence for excitation of the $8^{+}$ level. The corresponding effect on elastic scattering shows up as large cross-section reductions for ${}^{152}{Sm}$ compared with ${}^{148}{Sm}$ at all angles beyond 60°. The same sort of coupled elastic-inelastic effects are evinced by the ${}^{150}{Sm}$ cross sections, but are less marked. We show that these deformation effects are not explained using the usual coupled-channel optical model. The distribution of inelastic scattering strength to many levels of several shape transitional nuclei shows marked enhancements above statistical model expectations for the collective levels at the expense of cross sections to higher excited levels. The total nonelastic cross sections for all of these nuclei are about equal, indicating that deformation effects principally redistribute the scattering strength to emphasize collective levels strongly coupled to the ground state.

NUCLEAR REACTIONS ${}^{148, 150, 152}{Sm} (n, n)$ , ( $n, n^{'}$ ), ( $n, n^{'} γ$ ), $E_{n} = 2.47$ MeV; measured $σ (θ)$ . Coupled-channel model and statistical model analysis.

Statistical model radiation widths for $75 < A < 130$ and the enhancement of $P$ -wave neutron capture for $A \approx 90$

C. H. Johnson

Phys. Rev. C 16, 2238 (1977) - Published 1 December, 1977

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Statistical model calculations of radiation widths are made on the basis of the Axel-Brink hypothesis with two free parameters for the normalization and $A$ dependence of the low-energy tail of the giant electric dipole resonance. The two parameters are adjusted to fit known radiation widths with a standard deviation of about ±25% for $s$ -wave neutron resonance levels in nuclei with $75 < A < 130$ . The resulting $E 1$ strength functions are consistent with known values over a large mass region for transitions to low-lying states. The $M 1$ transitions are included. The level densities or nuclear temperatures for the analysis are deduced by fitting the backshifted Fermi-gas model to the total number of states near the ground state and to the $s$ -wave spacings at neutron binding. The low density of levels for $A \approx 90$ gives rise to statistical enhancement of $p$ -wave relative to $s$ -wave neutron radiative capture. The sum of calculated radiation widths for $p$ -wave resonances plus calculated radiation widths for $p$ -wave valency capture agree well with published experimental values.

NUCLEAR REACTIONS Calculated $〈 Γ_{γ} 〉$ , $75 < A < 130$ .

Mechanisms for Li and Be production in the ${}^{14}N$ + ${}^{12}C$ reaction

R. G. Stokstad, M. N. Namboodiri, E. T. Chulick, J. B. Natowitz, and D. L. Hanson

Phys. Rev. C 16, 2249 (1977) - Published 1 December, 1977

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Measurements of the yields of ${}^{6, 7}{Li}$ and ${}^{7, 9}{Be}$ have been made for the ${}^{14}N$ + ${}^{12}C$ reaction at $E_{{}^{14}N} = 86.9 and 157.0$ MeV. Statistical model calculations are compared with the data in order to determine the reaction mechanism. It is concluded that more than half of the total Li and Be yield at these bombarding energies arises from processes other than compound nucleus formation and the subsequent evaporation of a ${}^{6, 7}{Li}$ or ${}^{7, 9}{Be}$ nucleus. The most likely production mechanism at high bombarding energies appears to be the decay of a projectile-like fragment excited in a peripheral collision.

NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{14}N$ , ${}^{6, 7}{Li}$ ), ${}^{12}C$ ( ${}^{14}N$ , ${}^{7, 9}{Be}$ ), $E = 86.9 and 157.0$ MeV; measured $σ (E, θ)$ ; compared with statistical model calculations.

High-spin states in ${}^{64}{Zn}$

J. C. Wells, Jr., L. G. Fugate, R. O. Sayer, R. L. Robinson, H. J. Kim, W. T. Milner, G. J. Smith, and R. M. Ronningen

Phys. Rev. C 16, 2259 (1977) - Published 1 December, 1977

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Levels in ${}^{64}{Zn}$ have been investigated via the ${}^{51}V ({}^{16}O, p 2 n)$ reaction with $E_{{}^{16}O} = 36 - 46$ MeV, and via the ${}^{59}{Co} ({}^{7}{Li}, 2 n)$ reaction with $E_{{}^{7}{Li}} = 18$ MeV. Measurements were made of $γ$ -ray singles and $γ - γ$ coincidence spectra, of $γ$ -ray angular distributions, and of Doppler broadening of $γ$ -ray lines. Level energies, decay modes, spins and parities, $γ$ -ray branching ratios, $γ$ -ray radiative admixtures, and lifetimes were extracted. Lifetimes of levels were also determined by the Doppler-shift recoil-distance technique. There is a strongly excited band with the highest member observed being a $6^{+}$ state at 3994 keV. There is some evidence for a second even-parity band and for an odd-parity band.

NUCLEAR REACTIONS ${}^{51}V ({}^{16}O, p 2 n)$ $E = 36 - 46$ MeV; ${}^{59}{Co} ({}^{7}{Li}, 2 n)$ $E = 18$ MeV; measured $E_{γ}$ , $I_{γ}$ , $γ (θ)$ , $Δ E_{γ} (τ)$ . ${}^{64}{Zn}$ deduced levels, $J$ , $π$ , $δ$ , $γ$ branching, lifetimes.

High-spin states in ${}^{70}{Ge}$

R. L. Robinson, H. J. Kim, R. O. Sayer, J. C. Wells, Jr., R. M. Ronningen, and J. H. Hamilton

Phys. Rev. C 16, 2268 (1977) - Published 1 December, 1977

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The high-spin states of ${}^{70}{Ge}$ have been studied through observation of $γ$ rays from the reactions ${}^{60}{Ni} ({}^{12}C, 2 p)$ and ${}^{65}{Cu} ({}^{7}{Li}, 2 n)$ . Measurements were made of the $γ$ -ray singles and $γ - γ$ coincidence spectra, of the $γ$ -ray angular distributions, of the Doppler broadening for $γ$ -ray lines, and of the $γ - γ$ angular correlations. Level energies, spins and parities, and $γ$ -ray radiation admixtures were extracted. There is a strongly excited yrast band with the highest member observed being an $8^{+}$ state at 4433 keV. There is some evidence for a second even-parity band and for several odd-parity states with irregular level spacing.

NUCLEAR REACTIONS ${}^{60}{Ni} ({}^{12}C, 2 p)$ $E = 30 - 39$ MeV; ${}^{65}{Cu} ({}^{7}{Li}, 2 n)$ $E = 16 - 19$ MeV; measured $E_{γ}$ , $I_{γ}$ , $γ (θ)$ , $γ γ (θ)$ , Doppler broadening. ${}^{70}{Ge}$ deduced levels, $J$ , $π$ , $δ$ , $γ$ branching, $T_{\frac{1}{2}}$ .

Quasimolecular states in the ${}^{12}C$ - ${}^{12}C$ system

Jae Y. Park, Walter Greiner, and Werner Scheid

Phys. Rev. C 16, 2276 (1977) - Published 1 December, 1977

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Quasimolecular resonance structures in the ${}^{12}C$ - ${}^{12}C$ system are studied in the framework of the coupled channel formalism in the energy range $E_{c . m .} = 5 - 14$ MeV. The influence of the coupling of the first excited $2^{+}$ state in ${}^{12}C$ on the resonance structures is investigated by choosing various types of coupling potentials. The intermediate structures in the reflection and transition coefficients and cross sections can be interpreted with the double resonance mechanism.

NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{12}C$ , ${}^{12}C$ ), quasimolecular states, coupling potentials, coupled channel calculations for $σ (θ)$ .

Excitation of the highly-excited rotational band in ${}^{24}{Mg}$ by ${}^{10}B$ + ${}^{14}N$

N. Marquardt, W. Hoppe, and D. Siegel

Phys. Rev. C 16, 2291 (1977) - Published 1 December, 1977

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Evidence is presented for populating the $12^{+}$ and $14^{+}$ members of the excited ${}^{12}C$ + ${}^{12}C$ rotational band in ${}^{24}{Mg}$ by the ${}^{10}B$ + ${}^{14}N$ entrance channel. Excitation functions of the ${}^{10}B ({}^{14}N, α) {}^{20}{Ne}$ reaction close to 0° and 180° near the Coulomb barrier exhibit pronounced resonances and forward-backward cross-section asymmetries at the energies of these two ${}^{12}C$ + ${}^{12}C$ resonances.

NUCLEAR REACTIONS ${}^{10}B ({}^{14}N, α)$ , $E = 9 - 24$ MeV; measured $σ (E)$ close to 0° and 180°; deduced energies and widths of intermediate structures in ${}^{24}{Mg}$ .

Photofission of ${}^{232}{Th}$ with 9, 15, and 38 MeV peak bremsstrahlung

J. C. Hogan, A. E. Richardson, J. L. Meason, and H. L. Wright

Phys. Rev. C 16, 2296 (1977) - Published 1 December, 1977

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The mass-yield distribution of fission products following photofission of ${}^{232}{Th}$ using peak bremsstrahlung energies of 9, 15, and 38 MeV were measured by $γ$ spectrometry for 25 mass chains in the light and heavy mass wings. Fission yields for mass chains 85, 87, 88, 138, and 146 were measured for the first time for the photofission of ${}^{232}{Th}$ in this work. Several fractional chain yields were measured and various postulates of charge distribution were tested to correlate the experimental data. The Nethaway modified empirical Coryell method showed the best correlation with the observed charge distributions. Evidence for fine structure was observed from the 9 and 15 MeV irradiations in both the heavy and light mass wings with peaks occurring at $A = 134 and 93$ , respectively. The inner portions of the mass wings both exhibited increasing splay as the irradiation energy was increased, indicating that symmetric fission was enhanced with increased energy.

NUCLEAR REACTIONS, FISSION ${}^{232}{Th} (γ, f)$ , $E_{(peak bremsstrahlung)} = 9, 15, and 38$ MeV; measured mass-yield distribution, 25 mass chains, heavy, light mass wings by $γ$ spectrometry; measured several fractional yields, tested several charge distribution postulates, Ge (Li) detectors, 3.34 keV at 1.33 MeV, 2.3 keV at 1.33 MeV.

$A$ -dependent shift of the peak in the $π$ -nucleus total cross section

J. E. Sedlak and W. A. Friedman

Phys. Rev. C 16, 2306 (1977) - Published 1 December, 1977

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We relate the $A$ -dependent shift of the peak in the $π$ -nucleus total cross section to geometric and refractive effects. By comparing calculations with and without refractive corrections we show that wave-bending features acting on peripheral partial waves and varying systematically with energy and $A$ are primarily responsible for the shift.

NUCLEAR REACTIONS Scattering theory, $π$ -nucleus total cross section, $E = 100 - 200$ MeV.

Deexcitation gamma rays from the interaction of 70-MeV pions with $s - d$ shell nuclei

M. Zaider, D. Ashery, S. Cochavi, S. Gilad, M. A. Moinester, Y. Shamai, and A. I. Yavin

Phys. Rev. C 16, 2313 (1977) - Published 1 December, 1977

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The interaction of 70-MeV positive and negative pions with $s - d$ shell nuclei was studied via measurements of the deexcitation $γ$ rays from residual nuclei produced in the reactions. Cross sections for producing specific levels in the residual nuclei were measured. The results are compared with Monte Carlo calculations of intranuclear cascades, followed by evaporation processes. In order to take into account the special features of the prompt $γ$ -ray technique, the probability for leaving the residual nuclei at different regions of excitation, together with measured $γ$ -ray branching ratios, are incorporated into the calculated cross sections. Good agreement is found between measured and calculated cross sections for reactions involving the removal of four or more nucleons. For such reactions, the calculations are dominated by pion absorption processes. The cross sections for the removal of an $α$ -equivalent cluster from T = 0 nuclei have about the same strength as those corresponding to the removal of a triton cluster from the neighboring $T = \frac{1}{2}$ nuclei. This suggests that the final nucleus, rather than the removed particle, is mainly responsible for the observed strength. The cross sections for single-nucleon-removal reactions do not agree with the calculations.

NUCLEAR REACTIONS ${}^{23}{Na}$ , Mg, ${}^{27}{Al}$ , ${}^{28}{Si}$ , ${}^{31}P$ , ${}^{32}S$ , ${}^{39}K$ , ${}^{40}{Ca} (π^{\pm}, χ γ)$ , $E_{π} = 70$ MeV, Ge(Li) detector, measured cross sections for producing specific levs in residual nuclei, calculated $σ$ .

Field theoretic treatment of $π$ -nuclear scattering

Gerald A. Miller

Phys. Rev. C 16, 2325 (1977) - Published 1 December, 1977

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The dynamical assumption that single mesons are emitted or absorbed by nucleons is applied to $π$ -nucleus scattering and leads to a $π$ -nucleus Low equation. With the neglect of multinucleon currents and true meson absorption, the $π$ -nucleus Low equation is shown to be equivalent to a linear equation of the same form as in standard theories except for a striking propagator modification arising from the energy dependence of the driving term. The use of a corresponding linear equation for $π$ -nucleon scattering enables us to derive a field-theoretic multiple-scattering series. It is found that the propagator modification eliminates the Kisslinger singularity, reduces the Lorentz-Lorenz effect and local field corrections. The effect of true meson absorption on $π$ -nucleus elastic scattering is also examined and found to be somewhat important at low (∼50 MeV) energies but negligible (due to strong first-order optical absorption) for energies greater than 100 MeV.

NUCLEAR REACTIONS Scattering theory, $π$ -nucleon scattering, $π - {}^{16}O$ scattering, $E = 50 - 275$ MeV.

Scattering of pions by deuterons at low and medium energies

Erasmo M. Ferreira, L. Pinguelli Rosa, and Zieli D. Thomé

Phys. Rev. C 16, 2353 (1977) - Published 1 December, 1977

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We apply the multiple scattering method to calculate the differential cross sections for elastic $π d$ scattering in the low and medium energy regions, showing the importance of the proper treatment of the kinematics in the two body collision. Our results are compared with all existing experimental data in these energy regions. We show that the large angle elastic scattering at medium energies is highly sensitive to details of the deuteron structure and of the calculation procedure, and provides an excellent ground to study the properties of the meson-deuteron and of the off-shell meson-nucleon interactions.

NUCLEAR REACTIONS Pion deuteron elastic scattering. Multiple scattering calculation; Fermi motion, kinematical ambiguities, and off-energy-shell effects. Evaluation of $\frac{d σ}{d Ω}$ , low and intermediate energies.

Pion cross section measurements on aligned ${}^{165}{Ho}$ in the (3,3) resonance region

T. R. Fisher, J. A. Becker, B. A. Watson, H. Marshak, G. R. Burleson, M. D. Cooper, D. C. Hagerman, I. Halpern, M. J. Jakobson, R. H. Jeppeson, K. F. Johnson, L. D. Knutson, R. E. Marrs, H. O. Meyer, and R. P. Redwine

Phys. Rev. C 16, 2367 (1977) - Published 1 December, 1977

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The removal cross section $σ (Ω)$ for the interaction of $π^{+}$ and $π^{-}$ with aligned ${}^{165}{Ho}$ has been measured at $E_{π} = 115, 165, and 240$ MeV employing a single crystal holmium target with a nuclear alignment $B_{2} = - 0.44$ . The range of $Ω$ was from 0.05 to 0.55 sr. The data on $σ (Ω)$ and $Δ σ (Ω)$ , the difference between the aligned and unaligned cross sections, are compared with the predictions of a coupled-channels optical model calculation employing parameters from recent muonic x-ray data.

Low-lying energy levels of ${}^{145}{Pm}$

Z. Roller-Ivanović, A. Ljubičić, V. Paar, and B. A. Logan

Phys. Rev. C 16, 2376 (1977) - Published 1 December, 1977

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The decay scheme of ${}^{145}{Sm}$ has been investigated. In addition to the ground-state transition, the 492 keV second excited state of ${}^{145}{Pm}$ has been observed to deexcite with a (1.6 ± 0.1)% cascade transition through the 61 keV first excited level. This branching ratio is discussed on a theoretical basis, in terms of a particle-vibrator coupling model. No evidence was found for a previously reported 121 keV level in ${}^{145}{Pm}$ .

RADIOACTIVITY ${}^{145}{Sm}$ ; measured $E_{γ}$ , $I_{γ}$ ; deduced low energy levels of ${}^{145}{Pm}$ . Ge(Li) detector. 2.5 keV at 1332 keV.

Test of time reversal invariance in ${}^{57}{Fe}$

N. K. Cheung, H. E. Henrikson, and F. Boehm

Phys. Rev. C 16, 2381 (1977) - Published 1 December, 1977

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An experiment has been performed to test time reversal invariance by observing the angular distribution of the linear polarization of the mixed $E 2$ and $M 1$ 122 keV $γ$ rays in ${}^{57}{Fe}$ emitted from oriented ${}^{57}{Co}$ nuclei. Nuclear orientation was achieved with a high magnetic field (the 288 kG hyperfine field of ${}^{57}{Co}$ in an iron lattice) and a low temperature (16.5 to 18 mK obtained with a ${}^{3}{He}$ - ${}^{4}{He}$ dilution refrigerator). If time reversal invariance is violated, a term in the angular distribution of the form $(\vec{J} \cdot \vec{k} \times \vec{E}) (\vec{J} \cdot \vec{k}) (\vec{J} \cdot \vec{E}) sin η$ would be present, where the vectors $\vec{k}$ and $\vec{E}$ describe the propagation and linear polarization of the $γ$ ray, respectively, and $\vec{J}$ is the nuclear orientation vector. The quantity $η$ is the phase angle between the $E 2$ and $M 1$ matrix elements of the $γ$ transition. In our experiment the linear polarization was measured with a Compton polarimeter using an aluminum scatterer and NaI(Tl) detectors. From the observed asymmetry of $A = (- 0.35 \pm 0.78) \times 10^{- 5}$ , a value of $sin η = (- 3.1 \pm 6.5) \times 10^{- 4}$ was obtained. This result is consistent with time reversal invariance. Possible small contributions to the phase angle from atomic and nuclear final state effects are discussed.

RADIOACTIVITY ${}^{57}{Fe}$ ; measured lin. pol. of 122 keV $γ$ from pol. nuclei. Deduced rel. phase of $E 2$ , $M 1$ .

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Level structure of ${}^{173}{Yb}$ via the ( $d, p$ ) and ( $d, t$ ) reactions

Energy dependence of the ${}^{119}{Sn} (p, n) {}^{119}{Sn}$ (IAS) reaction

( $d, p$ ) reactions on ${}^{124}{Sn}$ , ${}^{130}{Te}$ , ${}^{138}{Ba}$ , ${}^{140}{Ce}$ , ${}^{142}{Nd}$ , and ${}^{208}{Pb}$ below and near the Coulomb barrier

$E 2$ and $E 4$ reduced matrix elements of ${}^{154, 156, 158, 160}{Gd}$ and ${}^{176, 178, 180}{Hf}$

Coulomb excitation measurements of reduced $E 2$ and $E 4$ transition matrix elements in ${}^{156, 158}{Dy}$ , ${}^{162, 164}{Er}$ , and ${}^{168}{Yb}$

Strong collective excitations in low energy neutron scattering from transitional nuclei

Statistical model radiation widths for $75 < A < 130$ and the enhancement of $P$ -wave neutron capture for $A \approx 90$

Mechanisms for Li and Be production in the ${}^{14}N$ + ${}^{12}C$ reaction

High-spin states in ${}^{64}{Zn}$

High-spin states in ${}^{70}{Ge}$

Quasimolecular states in the ${}^{12}C$ - ${}^{12}C$ system

Excitation of the highly-excited rotational band in ${}^{24}{Mg}$ by ${}^{10}B$ + ${}^{14}N$

Photofission of ${}^{232}{Th}$ with 9, 15, and 38 MeV peak bremsstrahlung

$A$ -dependent shift of the peak in the $π$ -nucleus total cross section

Deexcitation gamma rays from the interaction of 70-MeV pions with $s - d$ shell nuclei

Field theoretic treatment of $π$ -nuclear scattering

Scattering of pions by deuterons at low and medium energies

Pion cross section measurements on aligned ${}^{165}{Ho}$ in the (3,3) resonance region

Low-lying energy levels of ${}^{145}{Pm}$

Test of time reversal invariance in ${}^{57}{Fe}$

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