Recent Articles

Structure, directional-correlation, and lifetime measurements in ${}^{95}{Tc}$ via ${}^{95}{Mo} (p, n γ)$ reaction spectrometry

D. G. Sarantites and A. C. Xenoulis

Phys. Rev. C 10, 2348 (1974) - Published 1 December, 1974

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The level structure and the decay properties of levels in ${}^{95}{Tc}$ up to 2324 keV of excitation have been investigated via measurements of excitation functions of singles $γ$ rays and via $n γ$ - and $γ γ$ -coincidence experiments following the ${}^{95}{Mo} (p, n γ)$ reaction with proton energies between 3.1 and 6.5 MeV. From these experiments and from high resolution singles energy and directional-correlation measurements an extended decay scheme has been obtained which included 38 levels in ${}^{95}{Tc}$ and incorporated 106 $γ$ rays. New levels at 882.10 (13/ $2^{+}$ ), 957.12 (11/ $2^{+}$ ), 1213.10 (9/ $2^{+}$ ), 1214.53 (7/ $2^{-}$ ), 1275.86 (3/ $2^{-}$ ), 1281.46 (7/ $2^{+}$ ), 1307.18 (11/ $2^{+}$ ), 1631.97 (9/ $2^{+}$ , 11/ $2^{+}$ ), 1694.50 (3/2 — 7/2), 1920.00 (1/2 — 5/2), 1920.98 (9/ $2^{\pm}$ ), 1958.94 (9/ $2^{\pm}$ , 7/ $2^{+}$ ), 2032.31 (7/ $2^{+}$ , 9/ $2^{\pm}$ ), 2210.5, and 2219.7 keV with the assigned $J^{π}$ values in parentheses were postulated. Possible levels at 1033.85 (1/ $2^{\pm}$ ), 1837.5, 2164.1, 2236.8, 2240.6, and 2318.2 keV are also proposed. The singles directional correlations for many transitions provided (i) reliable branching ratios, (ii) $J^{π}$ assignments, and (iii) multipole mixing ratios $δ (\frac{E 2}{M 1})$ from analysis of the correlations via the compound statistical theory for nuclear reactions. Lifetimes for 22 states in ${}^{95}{Tc}$ and lower limits for 7 additional states were obtained by the Doppler-shift-attenuation method via the ${}^{95}{Mo} (p, n γ)$ reaction at 4.38 and 4.88 MeV. The lifetimes were extracted from singles spectra taken in the presence of standards at seven or nine angles between 0° and 90° to the beam direction, by employin a careful centroid shift analysis of the data. For a good number of transitions in ${}^{95}{Tc}$ values or limits for $B (E 1)$ , $B (E 2)$ , and $B (M 1)$ were obtained. The present results would support a description in terms of three quasiparticle configurations with coupling to the quadrupole vibrations.

NUCLEAR REACTIONS ${}^{95}{Mo} (p, n γ) {}^{95}{Tc}$ , $E_{p} = 3.1 - 6.5$ MeV, enriched targets. Measured $E_{γ}$ , $I_{γ}$ , $I_{γ} (θ)$ , $σ (E_{p})$ , $Δ E_{γ} (τ)$ , $γ - γ$ coinc., $n - γ$ coinc., deduced ${}^{95}{Tc}$ levels, thresholds, branching ratios, $τ$ , $δ (\frac{E 2}{M 1})$ , $B (E 2)$ , $B (M 1)$ , and $B (E 1)$ values; Ge(Li) detectors, Ge(Li)-NaI(Tl) anti-Compton spectrometer, NE-213 scintillation detector.

Level density and spin cutoff parameters from continuum ( $p, n$ ) and ( $α, n$ ) spectra

S. M. Grimes, J. D. Anderson, J. W. McClure, B. A. Pohl, and C. Wong

Phys. Rev. C 10, 2373 (1974) - Published 1 December, 1974

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Neutron spectra produced by ( $p, n$ ) reactions on ${}^{48}{Ti}$ , ${}^{49}{Ti}$ , ${}^{55}{Mn}$ , ${}^{58}{Fe}$ , and ${}^{63}{Cu}$ and ( $α, n$ ) reactions on ${}^{45}{Sc}$ , ${}^{49}{Ti}$ , ${}^{51}V$ , ${}^{52}{Cr}$ , ${}^{58}{Fe}$ , ${}^{59}{Co}$ , and ${}^{60}{Ni}$ have been measured at four bombarding energies. The component of the spectra corresponding to equilibrium (evaporation) processes was identified from the angular and bombarding energy dependence of the continuum cross sections. Level density parameters $a$ were deduced from the shape of the equilibrium emission spectra and spin cutoff parameters $σ$ were obtained from the anistropy of the ( $α, n$ ) angular distributions. Theoretical values for $a$ and $σ$ were obtained from a thermodynamic calculation with realistic single particle levels; these agreed well with the measured values. In particular, the mass number $A$ dependence of $σ$ was reproduced by the calculation and results from the variation with $A$ of angular momentum values of single particle levels near the Fermi level.

NUCLEAR REACTIONS ${}^{48}{Ti}$ , ${}^{49}{Ti}$ , ${}^{55}{Mn}$ , ${}^{58}{Fe}$ , ${}^{63}{Cu} (p, n)$ , $E = 8 - 15$ MeV; ${}^{45}{Sc}$ , ${}^{49}{Ti}$ , ${}^{51}V$ , ${}^{52}{Cr}$ , ${}^{58}{Fe}$ , ${}^{59}{Co}$ , ${}^{60}{Ni} (α, n)$ , $E = 12 - 20$ MeV; measured $σ (E_{n}, θ)$ ${}^{48}V$ , ${}^{49}V$ , ${}^{52}{Cr}$ , ${}^{54}{Mn}$ , ${}^{55}{Fe}$ , ${}^{58}{Co}$ , ${}^{61}{Ni}$ , ${}^{62}{Cu}$ , ${}^{63}{Zn}$ deduced level density parameters. ${}^{48}V$ , ${}^{52}{Cr}$ , ${}^{54}{Mn}$ , ${}^{55}{Fe}$ , ${}^{61}{Ni}$ , ${}^{62}{Cu}$ , ${}^{63}{Zn}$ deduced spin cutoff parameters. Isotopically separated and natural targets.

Extension of the isobar model for intranuclear cascades to 1 GeV

G. D. Harp

Phys. Rev. C 10, 2387 (1974) - Published 1 December, 1974

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An intranuclear cascade model is proposed for studying pion and nucleon induced reactions in the region of single pion production. The model explicitly considers the production and subsequent interactions of (3,3) isobars. The predictions of the model are compared with experimental data from proton induced reactions such as pion production yields, pion and proton energy and angular distributions, and spallation yields. The model gives a fair to excellent representation of all these data.

Inelastic scattering of thermal neutrons by nuclear isomers

Bernard Hamermesh

Phys. Rev. C 10, 2397 (1974) - Published 1 December, 1974

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An attempt to measure the radiationless decay of an isomer has been made by studying the reaction ${}^{123}{Te}^{m} (n, n^{'}) {}^{123}{Te}$ . The ${}^{123}{Te}^{m}$ (104 day) was placed in a beam of thermal neutrons. The transfer of the excitation energy of the isomer to the passing slow neutron produces highly monochromatic neutrons at 89 keV. An upper limit for the cross section was determined as 20 mb.

NUCLEAR REACTIONS ${}^{123}{Te}^{m} (n, n^{'}) {}^{123}{Te}$ ; determined upper limit for $σ$ .

${}^{92, 98}{Mo} (d, α) {}^{90, 96}{Nb}$ reactions and particle-hole multiplets

J. R. Comfort, H. T. Fortune, G. C. Morrison, and J. V. Maher

Phys. Rev. C 10, 2399 (1974) - Published 1 December, 1974

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The ${}^{92, 98}{Mo} (d, α) {}^{90, 96}{Nb}$ reactions have been studied at a bombarding energy of 17 MeV. Attention is given to the states previously observed in ( ${}^{3}{He}, t$ ) reactions that are thought to arise from simple particle-hole multiplets. Distorted-wave (DW) calculations were carried out with spectroscopic amplitudes calculated from assumed simple configurations. The DW calculations are found to be sensitive to variations in a number of parameters. It is found that the normalization constants needed to fit the observed cross sections vary widely for members of a single multiplet. In addition, the average normalization constants needed for states of the ${(g_{\frac{9}{2}})}^{2}$ multiplet in ${}^{90}{Nb}$ and the ( $g_{\frac{9}{2}} d_{\frac{5}{2}}$ ) multiplet in ${}^{96}{Nb}$ differ by a factor of 4.

NUCLEAR REACTIONS ${}^{92, 98}{Mo} (d, α) {}^{90, 96}{Nb}$ , $E = 17$ MeV; measured $σ (E_{α}, θ)$ , $θ = 11 - 90 °$ , $Δ θ = 4 - 10 °$ ; enriched targets; resolution 25-30 keV. Deduced $J^{π}$ , $L$ multiplet assignments. DWBA analysis.

Linear momentum transfer in reactions between 140-MeV ${}^{4}{He}$ ions and heavy nuclei

V. E. Viola, Jr., C. T. Roche, W. G. Meyer, and R. G. Clark

Phys. Rev. C 10, 2416 (1974) - Published 1 December, 1974

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The fission of ${}^{238}U$ , ${}^{209}{Bi}$ , and ${}^{197}{Au}$ induced by 140-MeV ${}^{4}{He}$ ions has been studied in order to investigate the target-projectile reaction mechanism. The fission-fragment angular correlation technique was used to measure the linear momentum transfer in these reactions. It is found that an upper limit of (49.3≥4.4)% of the fission in ${}^{238}U$ results from the complete fusion of target and projectile. The incomplete fusion component of the ${}^{238}U$ fission cross section includes a large fraction of high linear momentum transfer events, presumably produced in reactions where preequilibrium decay and/or deep knockout reactions are highly probable. The fission of ${}^{197}{Au}$ and ${}^{209}{Bi}$ is found to proceed almost completely via a complete fusion mechanism at this energy. The complete fusion cross section for ${}^{238}U$ reactions with 140-MeV ${}^{4}{He}$ ions is compared with that predicted from semiclassical collision models derived for heavy ion reactions.

NUCLEAR REACTIONS, FISSION ${}^{238}U (α, f)$ , ${}^{209}{Bi} (α, f)$ , ${}^{197}{Au} (α, f)$ , $E = 140$ MeV; measured $σ_{f}$ , fragment-fragment angular correlation; deduced linear momentum transfer distribution, $l_{crit}$ .

17.2-MeV proton inelastic scattering from low-lying unnatural-parity states in ${}^{88}{Sr}$

F. E. Cecil, R. P. Chestnut, and R. L. McGrath

Phys. Rev. C 10, 2425 (1974) - Published 1 December, 1974

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The differential cross sections to the $1^{+}$ (3.487-MeV) and $3^{+}$ (3.635-MeV) levels in ${}^{88}{Sr}$ have been measured between laboratory angles of 20° and 110° in the inelastic scattering of 17.2-MeV protons. The measured cross sections are reasonably well predicted by distorted-wave Born-approximation calculations assuming realistic interactions and shell model wave functions spanning a large basis space. It is found that the calculated cross sections are dominated by the components in the wave functions involving the valence nucleons and that the core polarization is relatively unimportant.

NUCLEAR REACTIONS ${}^{88}{Sr} (p, p^{'})$ , $E = 17.2$ MeV; measured $σ (E_{p^{'}}, θ)$ ; enriched target, microscopic DWBA analysis, $θ = 20 ° - 110 °$ .

Study of the lowest-lying $4^{-}$ states in ${}^{90}{Zr}$ and ${}^{92}{Zr}$

R. P. chestnut, F. E. Cecil, and R. L. McGrath

Phys. Rev. C 10, 2434 (1974) - Published 1 December, 1974

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Using particle $γ$ -coincident techniques, an upper limit of about 8 μb/sr is placed on the forward angle cross section for the excitation in ( $p, p^{'}$ ) at $E_{p} = 17.2$ MeV of the $4^{-}$ state in ${}^{90}{Zr}$ at 2.738 MeV. This upper limit is consistent with distorted-wave Born-approximation calculations using realistic interactions and reasonable wave functions. A $4^{-}$ state in ${}^{92}{Zr}$ is identified at 2.740 ± 0.010 MeV through the reaction ${}^{93}{Nb} (d, {}^{3}{He}) {}^{92}{Zr}$ at $E_{d} = 17.2$ MeV.

NUCLEAR REACTIONS ${}^{90}{Zr} (p, p^{'} γ)$ , ${}^{93}{Nb} (d, {}^{3}{He})$ , $E_{p} = 17.2$ MeV, $E_{d} = 17.2$ MeV; measured $σ (E_{p^{'}}, θ)$ , $σ (E_{{}^{3}{He}}, θ)$ ; calculated $σ (E_{p^{'}}, θ)$ microscopic DWBA; ${}^{92}{Zr}$ level measured, deduced $J^{π}$ .

Unusual back-angle scattering and the significance of coupled channels in the ${}^{60}{Ni} (α, α^{'})$ reactin at $E_{α} = 40$ MeV

M. B. Lewis, C. B. Fulmer, D. C. Hensley, C. C. Foster, N. M. O'Fallon, S. A. Gronemeyer, and W. W. Eidson

Phys. Rev. C 10, 2441 (1974) - Published 1 December, 1974

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Cross sections were measured for elastic and inelastic scattering of 40.1-MeV $α$ particles from ${}^{60}{Ni}$ over the range $θ = 153 - 189 °$ . The 180° cross section for inelastic scattering from the $2^{+}$ excited state at 2.16 MeV was found to be more than an order of magnitude larger than that for the first excited $2^{+}$ state at 1.33 MeV and nearly an order of magnitude larger than that for the elastic scattering. The phase of the angular distribution for the 2.16-MeV level is opposite to that of the 1.33-MeV level, but is the same as the elastic scattering. The data are compared with predictions of compound nucleus and coupled-channel reaction theory. While the compound nucleus reaction mechanism does not account qualitatively for these data, the coupled-channel approach is much more successful and indicates that the absorption term in the optical model potential is determined in a very sensitive way by the backangle elastic and inelastic scattering.

NUCLEAR REACTIONS ${}^{60}{Ni} (α, α^{'})$ , $E = 40.1$ MeV; measured absolute $σ (θ)$ , $θ = 153 - 189 °$ , coupled-channel analysis.

Charged particle $Q$ values for reactions on C, Cr, Fe, Co, and Ni

P. L. Jolivette, J. D. Goss, G. L. Marolt, A. A. Rollefson, and C. P. Browne

Phys. Rev. C 10, 2449 (1974) - Published 1 December, 1974

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$Q$ values were measured for 27 reactions on targets of ${}^{12}C$ , ${}^{54}{Cr}$ , ${}^{54, 56}{Fe}$ , ${}^{59}{Co}$ , and ${}^{58, 60, 62, 64}{Ni}$ with resulting uncertainties of 0.7 to 3.2 keV. Care was taken to define sources of error. A $χ^{2}$ test on an interconnected set of 19 measurements indicates internal consistency and a comparison of eight ( $d, p$ ) $Q$ values with ( $n, γ$ ) numbers shows excellent agreement. A mass evaluation was performed on a truncated region centered on Co. The results indicate that the 1971 values for the masses of ${}^{55}{Cr}$ and ${}^{55}{Co}$ are in error. The uncertainties of the masses of ${}^{53}{Fe}$ and ${}^{61}{Co}$ are greatly reduced. The question of the ${}^{57}{Fe}$ mass raised in The 1971 Atomic Mass Evaluation is not entirely resolved and consequently the absolute values of some masses in this region are still uncertain to about 5 keV although the $Q$ values are improved.

NUCLEAR REACTIONS ${}^{54, 56}{Fe}$ , ${}^{59}{Co}$ , ${}^{58, 60, 62, 64}{Ni} (p, a)$ ; ${}^{12}C$ , ${}^{54}{Cr}$ , ${}^{54, 56}{Fe}$ , ${}^{59}{Co}$ , ${}^{58, 60, 62}{Ni} (d, p)$ ; ${}^{54, 56}{Fe}$ , ${}^{59}{Co}$ , ${}^{60, 62}{Ni} (d, t)$ ; ${}^{59}{Co}$ , ${}^{60, 62}{Ni} (d, a)$ ; ${}^{54}{Fe} ({}^{3}{He}, d)$ ; ${}^{54}{Fe} ({}^{3}{He}, a)$ ; ${}^{54}{Fe}$ , ${}^{59}{Co} (a, p)$ measured $Q$ values. ${}^{12}C (d, d)$ , ( $p, p$ ) measured $E_{x}$ . Mass adjustment.

Electric monopole admixtures in interband transitions of ${}^{154}{Gd}$

Y. Gono and T. T. Sugihara

Phys. Rev. C 10, 2460 (1974) - Published 1 December, 1974

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The in-beam conversion-electron spectrum for the reaction ${}^{154}{Sm} (α, 4 n) {}^{154}{Gd}$ has been obtained at 45 MeV. Strong $E 0$ components are observed for interband transitions between states in the $β$ and ground bands up to at least spin 10 and probably also spin 12. The ratio of transition probabilities, $E 0$ to $E 2$ , is found to be essentially constant for $I_{β}$ in the range 2 to 10. No evidence for a dramatic change which might be associated with the backbending phenomenon is seen.

NUCLEAR REACTIONS ${}^{154}{Sm} (α, 4 n)$ , $E = 45$ MeV, enriched target; measured in-beam $I_{ce}$ , $I_{γ}$ . ${}^{154}{Gd}$ deduced ICC, $\frac{B (E 0)}{B (E 2)}$ .

Recoil properties of Ta isotopes produced in the interaction of high-energy protons with Bi and U

S. K. Chang, M. C. Cheney, and Nathan Sugarman

Phys. Rev. C 10, 2467 (1974) - Published 1 December, 1974

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Thick-target thick-catcher recoil properties were determined for neutron-deficient Ta isotopes produced in the interaction of 0.45- and 11.5-GeV protons with Bi and U. The production mechanism was shown to be a binary mass division process at 0.45 GeV. At 11.5 GeV, either a high-excitation-energy ("deep") spallation process or a fission process from light nuclei is a possible mechanism. The half-life of ${}^{179}{Ta}$ , measured on two samples over a period of two years, was determined to be 588 ± 10 days.

NUCLEAR REACTIONS ${}^{209}{Bi}$ and ${}^{238}U$ ( $p, f, and spallation$ ) ${}^{172 - 179}{Ta}$ , $E = 0.45, 11.5$ GeV. Measured thick-target recoil properties of Ta isotopes; reaction mechanisms proposed. Measured $T_{\frac{1}{2}} ({}^{179}{Ta}) = 588 \pm 10$ days.

Comparisons of predictions from two intranuclear-cascade models with measured secondary proton spectra at several angles from 62 - and 39 - MeV protons on various elements

H. W. Bertini, G. D. Harp, and F. E. Bertrand

Phys. Rev. C 10, 2472 (1974) - Published 1 December, 1974

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Detailed comparisons of correlated energy-angle proton spectra corresponding to continuum state transtions have been made between experimental data and two versions—Brookhaven National Laboratory (BNL) and Oak Ridge National Laboratory (ORNL)—of the intranuclear-cascade model for 62- and 39-MeV protons incident on carbon, iron, and bismuth. These energies were selected because detailed experimental data are available and because the energy limit of validity of the intranuclear-cascade approach could be examined. The calculated spectra are in good agreement (≤ 30%) with the shapes and magnitudes of the measured integral spectra for the 62-MeV reactions. However, the comparisons of the spectra at angles ≤ 20° and > 90° are poor. There is a much greater discrepancy in the correlated energy-angle data from reactions at 39 MeV. The BNL version, which contains the greater physical detail, tends to reduce the discrepancies in the spectral shape at small and large angles between the experimental data and the simpler intranuclear-cascade version (ORNL). Examples of these discrepancies are: a high estimated quasifree peak at small angles and a small scattering intensity at back angles. However, the BNL version reduces the particle yield for heavy targets so that the comparisons of the predicted absolute cross sections with the experimental data are often poor. The effects of reflection and refraction, which are included in the BNL version only, appear to be in the right direction to compensate for the discrepancies of the ORNL version, but some modification in the manner that this phenomenon is incorporated may be required to avoid the discrepancies in absolute cross sections.

NUCLEAR REACTIONS ${}^{12}C (p, p^{'} X)$ , ${}^{54}{Fe} (p, p^{'} X)$ , ${}^{209}{Bi} (p, p^{'} X)$ calculated $σ (E; E_{p^{'}}, θ)$ , $σ (E)$ ; $E = 39, 62$ MeV. Intranuclear-cascade models.

${}^{180}{Hf}$ energy levels deduced from thermal and average resonance neutron-capture $γ$ -ray spectra

D. L. Bushnell, D. J. Buss, and Robert K. Smither

Phys. Rev. C 10, 2483 (1974) - Published 1 December, 1974

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An energy level diagram for ${}^{180}{Hf}$ is developed on the basis of neutron-capture $γ$ -ray spectroscopy. Both thermal neutron capture and average resonance neutron-capture studies were made with isotopically enriched and natural Hf samples. The energies and intensities of the high-energy 7.4-4.7 MeV primary $γ$ transitions and the intermediate-energy 2.1-0.5 MeV $γ$ transitions were made with the in-pile ( $n, γ$ ) source facility at the Argonne research reactor using Ge(Li) $γ$ -ray detectors. The low-energy 1300-1330 keV $γ$ transitions were measured with the Argonne 7.7 m bent-crystal $γ$ -ray spectrometer which also uses an in-pile ( $n, γ$ ) source at the Argonne reactor. The final level scheme contains 41 levels with excitation energies up to 2.7 MeV. Twenty-six new levels are reported. Parity assignments are made for all but three of these levels. Unique spin assignments are made for 21 levels and the spin of 15 additional levels was limited to two choices. The possible existence of excited state rotational bands was explored. Two $K = 0$ excited state bands and a $K = 2$ excited state band were identified.

NUCLEAR REACTIONS ${}^{179}{Hf} (n, γ)$ , measured $γ$ specrum, $E_{γ}$ , $I_{γ}$ , 0.5-2.1 MeV, 4.7-7.4 MeV, Ge(Li) detector, thermal neutrons; measured $γ$ spectrum, $E_{γ}$ , $I_{γ}$ , 4.7-7.4 MeV, average resonance neutrons, Ge(Li) detector; measured $γ$ spectrum, $E_{γ}$ , $I_{γ}$ , 0.03-1.3 MeV, bent-crystal spectrometer, thermal neutrons. Developed level scheme ${}^{180}{Hf}$ , $J^{π}$ , $γ$ -ray branching ratios.

Proton- $γ$ angular correlations in the reaction ${}^{52}{Cr} (d, p γ) {}^{53}{Cr}$

W. Eyrich, S. Schneider, A. Hofmann, U. Scheib, and F. Vogler

Phys. Rev. C 10, 2512 (1974) - Published 1 December, 1974

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The reaction ${}^{52}{Cr} (d, p γ) {}^{53}{Cr}$ has been studied at a deuteron energy of 10 MeV up to an excitation energy in ${}^{53}{Cr}$ of about 5 MeV. The protons have been detected by use of a multidetector arrangement consisting of 8-11 silicon surface-barrier detectors.Particle- $γ$ coincidence measurements have been performed with a Ge(Li) detectro in and out of the reaction plane. Absolute double differential cross sections have been measured for particle angles between 20 and 160° for several transitions with $l$ transfers of 1, 2, 3, and 4. From differential and double differential cross sections the experimental particle- $γ$ angular correlation functions as a function of the particle angle have been extracted. The differential cross sections and the angular correlation functions have been analyzed with distorted-wave Born approximation. It turned out that deuteron potentials giving four half wave lengths of the wave function inside the potential well yield the best agreement with both the differential cross sections and the angular correlation functions. The influence of the spin orbit potential on the angular correlation was found to be less important.

NUCLEAR REACTIONS ${}^{52}{Cr} (d, p γ)$ , $E = 10$ MeV; measured differential and double differential cross sections. DWBA analyses of $l = 1, 3, and 4$ transitions; enriched target.

$Q_{β}$ values of neutron-rich Cs isotopes

K. Wünsch, H. Wollnik, and G. Siegert

Phys. Rev. C 10, 2523 (1974) - Published 1 December, 1974

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An on-line separator equipped with a thermal ion source was used to determine decay energies of mass-separated neutron-rich Cs fission products. From the $β$ spectrum end-point energies from singles experiments as well as from $β - γ$ coincidence experiments, the $Q_{β}$ values of ${}^{141, 142, 143, 144, 145}{Cs}$ were determined to be 4.95 ± 0.15 MeV, 6.77 ± 0.2 MeV, 5.65 ± 0.2 MeV, 8.1 ± 0.3 MeV, and 6.1 ± 0.5 MeV, respectively.

RADIOACTIVITY ${}^{141 - 145}{Cs}$ [from ${}^{235}U (n, f)$ ]; measured $β$ spectrum; deduced $Q_{β}$ ; mass-separated Cs activities.

Levels of ${}^{93}{Rb}$ , ${}^{93}{Sr}$ , and ${}^{93}Y$ fed in the decays of ${}^{93}{Kr}$ , ${}^{93}{Rb}$ , and ${}^{93}{Sr}$

E. Achterberg, F. C. Iglesias, A. E. Jech, J. A. Moragues, D. Otero, M. L. Pérez, A. N. Proto, J. J. Rossi, and W. Scheuer

Phys. Rev. C 10, 2526 (1974) - Published 1 December, 1974

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The $γ$ rays and conversion electrons following the $β^{-}$ decay of ${}^{93}{Kr}$ , ${}^{93}{Rb}$ , and ${}^{93}{Sr}$ have been measured by applying on-line mass-separation techniques to ${}^{235}U$ fission products. Level schemes for the three daughter nuclei are proposed based on the study of $γ$ -singles, $γ γ$ -coincidence, and internal-conversion electron spectra. Internal-conversion coefficients were determined for 10 transitions and the deduced multipolarities as well as $log ft$ values were combined with known reaction results to assign spins and parities. The half-life for the 758.63-KeV isomeric level in ${}^{93}Y$ was measured to be 85 ± 15 msec.

RADIOACTIVITY ${}^{93}{Kr}$ , ${}^{93}{Rb}$ , ${}^{93}{Sr}$ ; measured $E_{γ}$ , $I_{γ}$ , $γ γ$ coin, ICC; deduced $log ft$ , $Λ$ . ${}^{93}Y^{m}$ ; measured $T_{\frac{1}{2}}$ . ${}^{93}{Rb}$ , ${}^{93}{Sr}$ , ${}^{93}Y$ ; deduced levels, $J$ , $π$ . On-line measurement, mass-separated ${}^{235}U$ fission products.

$\frac{E 0}{E 2}$ transition strengths and interpretations of $0^{+}$ , $2^{+}$ states in ${}^{178}{Hf}$

J. H. Hamilton, K. Kumar, L. Varnell, A. V. Ramayya, P. E. Little, and Noah R. Johnson

Phys. Rev. C 10, 2540 (1974) - Published 1 December, 1974

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Six measured $X (\frac{E 0}{E 2})$ values of ${}^{178}{Hf}$ are reported and compared with nuclear models. Three of these values are considerably larger than the $β$ -vibrational model estimates. Experiments are suggested to test the possibility that large $X$ values indicate mostly proton excitations.

RADIOACTIVITY ${}^{178}W$ [from ${}^{181}{Ta} (p, 4 n)$ ; measured $E_{γ}$ , $I_{γ}$ , $I_{ce}$ , $γ γ (θ)$ ; deduced cc, $ρ$ , $X (\frac{E 0}{E 2})$ , enriched target.

Hauser-Feshbach calculation of the ${}^{252}{Cf}$ spontaneous-fission neutron spectrum

J. C. Browne and F. S. Dietrich

Phys. Rev. C 10, 2545 (1974) - Published 1 December, 1974

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The neutron spectrum from ${}^{252}{Cf}$ spontaneous fission has been calculated using the Hauser-Feshbach formalism. Details of the excitation energy and spin distributions have been included for 40 fission fragments chosen in a manner to average over the mass distribution and over pairing-energy effects. No arbitrary parameters were introduced into the calculation to produce a fit to the data. The results of the calculation are in good agreement with experimental data.

RADIOACTIVITY, FISSION ${}^{252}{Cf} (sf)$ ; calculated neutron spectrum; Hauser-Feshbach calculation.

$α$ -decay branching ratios for ${}^{151}{Tb}$ , ${}^{150 - 153}{Dy}$ , and ${}^{152 - 155}{Er}$

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

Phys. Rev. C 10, 2550 (1974) - Published 1 December, 1974

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The isotopes ${}^{152 - 155}{Er}$ and ${}^{151}{Tb}$ , ${}^{150 - 153}{Dy}$ were produced by bombarding ${}^{147}{Sm}$ and ${}^{144}{Nd}$ , respectively, with ${}^{12}C$ ions accelerated in the Oak Ridge isochronous cyclotron. With the use of a gas-jet-capillary transport system $α$ -particle, x-ray, and $γ$ -ray spectra were measured simultaneously and $α$ -decay branching ratios deduced for the above mentioned nuclides. The ratios were determined primarily by measuring the number of $K α_{1}$ x rays emitted and then applying appropriate correction factors to obtain the total number of electron capture and positron decays. In addition, for ${}^{150, 152, 153}{Dy}$ it was possible to deduce alternate, and thus independent, $α$ -decay branching ratios from $γ$ -ray spectral measurements. Within error limits the two sets of values were found to be in agreement. Because of the essentially equal half-lives of ${}^{151}{Tb}$ and ${}^{152}{Tb}$ the α branch for ${}^{151}{Tb}$ could not be determined from the $K α_{1}$ ray intensity; instead it was deduced solely on the basis of its known decay to levels in ${}^{151}{Gd}$ . Branches for ${}^{149}{Tb}$ , ${}^{149}{Tb}^{m}$ , and ${}^{150}{Tb}$ , as well as for the fine structure $α$ decays observed in the case of ${}^{153}{Dy}$ and ${}^{149, 151}{Tb}$ , were taken from a survey of published values. These data were combined with our own results and $α$ -decay reduced widths were calculated using the formalism developed by Rasmussen. As is customary, reduced widths for ground-state transitions between even-even nuclei were assumed to represent unhindered decay and then compared with values for the remaining $α$ decays. As we had found earlier for the neighboring odd- $Z$ holmium nuclides these latter reduced widths ranged from values close to those of even-even nuclei down to much smaller ones. This result is examined from the standpoint of what is known about spin assignments for states connected by specific $α$ -decay transitions.

RADIOACTIVITY ${}^{151}{Tb}$ , ${}^{150, 151, 152, 153}{Dy}$ , ${}^{152, 153, 154, 155}{Er}$ ; $I_{α}$ , $I$ ( $K α_{1}$ x ray), $I_{γ}$ , $E_{γ}$ ; measured $α$ -decay branching ratios; deduced $α$ -decay rates. ${}^{150, 152}{Tb}$ deduced levels, $J$ , $π$ .

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Structure, directional-correlation, and lifetime measurements in ${}^{95}{Tc}$ via ${}^{95}{Mo} (p, n γ)$ reaction spectrometry

Level density and spin cutoff parameters from continuum ( $p, n$ ) and ( $α, n$ ) spectra

Extension of the isobar model for intranuclear cascades to 1 GeV

Inelastic scattering of thermal neutrons by nuclear isomers

${}^{92, 98}{Mo} (d, α) {}^{90, 96}{Nb}$ reactions and particle-hole multiplets

Linear momentum transfer in reactions between 140-MeV ${}^{4}{He}$ ions and heavy nuclei

17.2-MeV proton inelastic scattering from low-lying unnatural-parity states in ${}^{88}{Sr}$

Study of the lowest-lying $4^{-}$ states in ${}^{90}{Zr}$ and ${}^{92}{Zr}$

Unusual back-angle scattering and the significance of coupled channels in the ${}^{60}{Ni} (α, α^{'})$ reactin at $E_{α} = 40$ MeV

Charged particle $Q$ values for reactions on C, Cr, Fe, Co, and Ni

Electric monopole admixtures in interband transitions of ${}^{154}{Gd}$

Recoil properties of Ta isotopes produced in the interaction of high-energy protons with Bi and U

Comparisons of predictions from two intranuclear-cascade models with measured secondary proton spectra at several angles from 62 - and 39 - MeV protons on various elements

${}^{180}{Hf}$ energy levels deduced from thermal and average resonance neutron-capture $γ$ -ray spectra

Proton- $γ$ angular correlations in the reaction ${}^{52}{Cr} (d, p γ) {}^{53}{Cr}$

$Q_{β}$ values of neutron-rich Cs isotopes

Levels of ${}^{93}{Rb}$ , ${}^{93}{Sr}$ , and ${}^{93}Y$ fed in the decays of ${}^{93}{Kr}$ , ${}^{93}{Rb}$ , and ${}^{93}{Sr}$

$\frac{E 0}{E 2}$ transition strengths and interpretations of $0^{+}$ , $2^{+}$ states in ${}^{178}{Hf}$

Hauser-Feshbach calculation of the ${}^{252}{Cf}$ spontaneous-fission neutron spectrum

$α$ -decay branching ratios for ${}^{151}{Tb}$ , ${}^{150 - 153}{Dy}$ , and ${}^{152 - 155}{Er}$

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