Recent Articles

Skyrme-force time-dependent Hartree-Fock calculations with axial symmetry

K. T. R. Davies and S. E. Koonin

Phys. Rev. C 23, 2042 (1981) - Published 1 May, 1981

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We discuss axially symmetric time-dependent Hartree-Fock calculations using a finite-range modification of the Skyrme energy functional. The finite-difference forms of the coordinate-space time-dependent Hartree-Fock equations, the method of time evolution, and other numerical aspects are presented. Detailed results for ${}^{84}{Kr}$ -induced deep-inelastic collisions with ${}^{208}{Pb}$ at $E_{lab} = 494$ MeV and with ${}^{209}{Bi}$ at $E_{lab} = 600 MeV and 714 MeV$ are compared with experiment.

NUCLEAR REACTIONS ${}^{84}{Kr}$ + ${}^{208}{Pb}$ at $E_{lab} = 494$ MeV and ${}^{84}{Kr}$ + ${}^{209}{Bi}$ at $E_{lab} = 600 and 714$ MeV, in the time-dependent Hartree-Fock approximation. Strongly damped collisions. Details of Skyrme force calculations with axial symmetry.

Fusion excitation functions for ${}^{16}O$ + ${}^{27}{Al}$ and ${}^{16}O$ + ${}^{24}{Mg}$ collisions

K. R. S. Devi, A. K. Dhar, and M. R. Strayer

Phys. Rev. C 23, 2062 (1981) - Published 1 May, 1981

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Fusion excitation functions have been calculated for the ${}^{16}O$ + ${}^{27}{Al}$ and ${}^{16}O$ + ${}^{24}{Mg}$ collisions using the time-dependent Hartree-Fock theory. The theoretical results are in good agreement with experiment and predict the existence of a lower angular momentum limit to fusion for $E_{lab} \geq 100$ MeV.

NUCLEAR REACTIONS ${}^{16}O$ + ${}^{24}{Mg}$ and ${}^{16}O$ + ${}^{27}{Al}$ fusion excitation functions in the time-dependent Hartree-Fock approximation.

Possible triaxial structures in ${}^{24}{Mg}$ from ${}^{16}O$ + ${}^{24}{Mg}$ elastic and inelastic scattering

J. S. Eck, J. Nurzynski, T. R. Ophel, P. D. Clark, D. F. Hebbard, and D. C. Weisser

Phys. Rev. C 23, 2068 (1981) - Published 1 May, 1981

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The energy level scheme for the low-lying collective levels of ${}^{24}{Mg}$ are reasonably described by an asymmetric rotor with $β_{2} = 0.52$ and $γ = 22 °$ . To further investigate possible triaxial structures in ${}^{24}{Mg}$ , we have measured elastic and inelastic scattering angular distributions for excitation of the lowest three excited states in ${}^{24}{Mg}$ at an ${}^{16}O$ bombarding energy of 67 MeV in the angular range $θ_{c . m .} = 10 - 65 °$ . The measured cross sections have been analyzed using coupled channels calculations assuming that ${}^{24}{Mg}$ behaves as (1) a symmetric rotor and (2) a triaxial rotor. Because of the fact that the $2_{2}^{+}$ and $4_{1}^{+}$ states in ${}^{24}{Mg}$ are unresolved, difficulty occurs in distinguishing between the two models. Considering ${}^{24}{Mg}$ to be a triaxial rotor, however, does yield a simple description of the bound states and scattering to the low-lying collective levels.

NUCLEAR REACTIONS ${}^{24}{Mg}$ ( ${}^{16}O$ , ${}^{16}O$ ) ${}^{24}{Mg}^{*}$ elastic and inelastic scattering $Q = 0.00, - 1.37, - 4.12, and - 4.23$ MeV at $E ({}^{16}O) = 67$ MeV. Measured $σ_{el} (θ)$ and $σ_{inel} (θ)$ for $θ_{c . m .} = 10 - 65 °$ , calculated $σ_{el} (θ)$ and $σ_{inel} (θ)$ using coupled channels and symmetric and triaxial rotor models.

Lifetime of the 1.04 MeV state in ${}^{18}F$ , measured through the inverse reaction ${}^{3}{He} ({}^{16}O, p) {}^{18}F$

J. Keinonen, H. -B. Mak, T. K. Alexander, G. C. Ball, W. G. Davies, J. S. Forster, and I. V. Mitchell

Phys. Rev. C 23, 2073 (1981) - Published 1 May, 1981

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The mean lifetime of the 1.04 MeV ( $J^{π} = 0^{+}, T = 1$ ) state in ${}^{18}F$ has been measured to be 2.7±0.7 fs using the inverse reaction ${}^{3}{He} ({}^{16}O, p) {}^{18}F$ and the Doppler-shift attenuation method. Targets of ${}^{3}{He}$ implanted into Al, Zr, Nb, and Au foils were employed in the measurements. The centroid shifts and Doppler-broadened line shapes observed at 0° were used in obtaining the lifetime value. The lifetime of the 1.04 MeV state is compared with theoretical predictions.

NUCLEAR REACTIONS ${}^{3}{He} ({}^{16}O, p) {}^{18}F$ , $E = 15.9$ MeV; measured Doppler-shift attenuation, $p γ$ coin. ${}^{18}F$ 1.04 MeV level deduced $τ$ .

High spin states in ${}^{156}{Yb}$ ( $N = 86$ )

C. J. Lister, D. Horn, C. Baktash, E. der Mateosian, O. C. Kistner, and A. W. Sunyar

Phys. Rev. C 23, 2078 (1981) - Published 1 May, 1981

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Yrast states in ${}^{156}{Yb}$ have been identified to spin and parity $J^{π} = 25^{-}$ at 7405 keV using the ${}^{144}{Sm} ({}^{16}O, 4 n) {}^{156}{Yb}$ ( $E = 70 - 120$ MeV) and ${}^{113}{In} ({}^{46}{Ti}, p 2 n) {}^{156}{Yb}$ ( $E = 190 - 210$ MeV) reactions together with standard $γ$ -ray spectroscopic techniques. Evidence was found for additional transitions extending to $J - 30$ at 9464 keV. One isomeric state was observed with $J^{π} = 11^{-}$ at $E_{x} = 3028$ keV, having $T_{\frac{1}{2}} = 6.0 \pm 0.5$ ns. The structure of this nucleus is compared with that of other $N = 86$ isotones. It appears that most of the features can be described in terms of relatively simple shell model configurations in a nearly spherical ( $| β | ≲ 0.1$ ) potential.

NUCLEAR REACTIONS ${}^{144}{Sm} ({}^{16}O, 4 n) {}^{156}{Yb}$ $E = 70 - 120$ MeV; ${}^{113}{In} ({}^{46}{Ti}, p 2 n) {}^{156}{Yb}$ $E = 190 - 210$ MeV. Measured $E_{γ}$ , $I_{γ}$ , linear polarizations, $γ - γ$ , $γ$ -x-ray, $γ$ -charged particle coincidences, pulsed beam lifetimes. Deduced level energies, branching ratios, spin and parity assignments, multipole mixing ratios, electromagnetic transition strengths. Ge(Li) detectors. Enriched targets. Comparison with systematic trends.

Band structure in ${}^{80}{Kr}$

D. L. Sastry, A. Ahmed, A. V. Ramayya, R. B. Piercey, H. Kawakami, R. Soundranayagam, J. H. Hamilton, C. F. Maguire, A. P. de Lima, S. Ramavataram, R. L. Robinson, H. J. Kim, and J. C. Wells

Phys. Rev. C 23, 2086 (1981) - Published 1 May, 1981

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The levels of ${}^{80}{Kr}$ have been investigated using in-beam $γ$ -spectroscopy techniques via the ${}^{70}{Zn} ({}^{12}C, 2 n) {}^{80}{Kr}$ reaction with 38.4 MeV ${}^{12}C$ ions. The energies, relative intensities, and angular distributions of the $γ$ rays were measured. The proposed level scheme shows four bands: three of even parity and one of odd parity. Two-quasiparticle-plus-rotor calculations for ${}^{80}{Kr}$ suggest that the even-parity band built on the ( $8^{+}$ ) state at 3701.6 keV has primarily a proton ${(g_{\frac{9}{2}})}^{2}$ configuration and the odd-parity band built on the $5^{-}$ state at 2861.0 keV has an essentially pure two-quasiproton $(f_{\frac{5}{2}}, g_{\frac{9}{2}}) 5^{-}$ configuration. The observed backbending in the yrast band is attributed to the crossing of the ground band and the excited positive-parity band.

NUCLEAR REACTIONS ${}^{70}{Zn} ({}^{12}C, 2 n)$ , $E = 33.0 - 38.4$ MeV; measured $E_{γ}$ , $I_{γ}$ , $γ (θ)$ DCO; deduced ${}^{80}{Kr}$ levels, $J$ , $π$ , and $γ$ branching; performed two-quasiparticle-plus-rotor model calculations.

Nonequilibrium aspects in relativistic nuclear collisions

J. Cugnon

Phys. Rev. C 23, 2094 (1981) - Published 1 May, 1981

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The possibility of splitting the inclusive cross section for relativistic nuclear collisions into a direct and a thermal component is examined. It is pointed out that the definition of a direct term is model dependent. Besides this difficulty, it is explained why two particle correlation measurements can give ambiguous information on the size of the direct component. The decomposition of the inclusive cross section in the context of Monte Carlo calculations, according to the number $n$ of collisions undergone by the ejected nucleons, is considered. Numerical results for Ne + Ne and Ca + Ca at $\frac{E}{A} = 800$ MeV show that the cross sections cannot be split into two parts that could be regarded as a direct and a thermal part, but rather indicate a continuously rising departure from equilibrium as $n$ decreases. Dominance of some values of $n$ in some regions of the momentum space is exhibited. The $Δ$ -particle spectra show a completely different pattern and look similar for all values of $n$ .

NUCLEAR REACTIONS Relativistic nucleus-nucleus collisions. Direct and thermal contributions. Nonequilibrium intermediate processes. ${}^{20}{Ne}$ + ${}^{20}{Ne}$ , ${}^{40}{Ca}$ + ${}^{40}{Ca}$ . $\frac{E}{A} = 800$ MeV.

Comparison of ${}^{252}{Cf}$ spontaneous fission with ${}^{250}{Cf} (t, p f)$

J. Weber, H. C. Britt, and J. B. Wilhelmy

Phys. Rev. C 23, 2100 (1981) - Published 1 May, 1981

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A comparison is presented of the total kinetic energy and yield distributions for ${}^{252}{Cf}$ spontaneous fission and ${}^{252}{Cf}$ excited to 5-9 MeV via a ${}^{250}{Cf} (t, p f)$ reaction. Systematic differences are observed between trends in these data and similar results for lighter actinides.

NUCLEAR REACTIONS, FISSION Measured total kinetic energy and yield distributions as a function of excitation energy for ${}^{252}{Cf}$ .

Kinetic energy and fragment mass distributions for ${}^{240}{Pu}$ (s.f.), ${}^{239}{Pu} (n_{th}, f)$ , and ${}^{240}{Pu} (γ, f)$

H. Thierens, A. De Clercq, E. Jacobs, D. De Frenne, P. D'hondt, P. De Gelder, and A. J. Deruytter

Phys. Rev. C 23, 2104 (1981) - Published 1 May, 1981

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Energy correlation measurements were performed for ${}^{240}{Pu}$ (s.f.), ${}^{239}{Pu} (n_{th}, f)$ , and the photofission of ${}^{240}{Pu}$ with 12-, 15-, 20-, and 30-MeV bremsstrahlung. The photofission cross section for ${}^{240}{Pu}$ was determined up to 30 MeV, which permitted the calculation of the average excitation energy $〈 E_{exc} 〉$ of the compound nucleus. The average total kinetic energy $〈 E_{k} 〉$ of the fragments for ${}^{240}{Pu}$ (s.f.) was found to be 1.2±0.5 MeV higher than for ${}^{239}{Pu} (n_{th}, f)$ . A decrease of $〈 E_{k} 〉$ , with $〈 E_{exc} 〉$ , $\frac{d 〈 E_{k} 〉}{d 〈 E_{exc} 〉} = - 0.37 \pm 0.08$ , is observed in the photofission of ${}^{240}{Pu}$ . Fragment shell effects are present in the kinetic energy and mass distributions for ${}^{240}{Pu}$ (s.f.). Changes in the measured distributions with increasing excitation energy of the compound nucleus ${}^{240}{Pu}$ are discussed in the framework of the scission point model of Wilkins et al.

RADIOACTIVITY Fission ${}^{240}{Pu}$ (s.f.). NUCLEAR REACTIONS Fission ${}^{239}{Pu} (n_{th}, f)$ , ${}^{240}{Pu} (γ, f)$ , $E_{γ_{max}} = 12, 15, 20, 30$ MeV; measured: photofission yields, fragment energies $E_{1}$ , $E_{2}$ ; deduced: $σ (γ, f)$ , $\frac{N (μ, E_{k})}{〈 E_{exc} (E_{e}) 〉}$ .

Spin dependence in intermediate energy $p$ -nucleus scattering

R. D. Amado, J. A. McNeil, and D. A. Sparrow

Phys. Rev. C 23, 2114 (1981) - Published 1 May, 1981

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We obtain closed form approximations for the spin dependent eikonal $p$ -nucleus scattering amplitudes. The polarization $P$ and spin rotation function $Q$ can be written in terms of the unpolarized elastic scattering cross section and two complex parameters related to the nucleon-nucleon spin orbit strength and range. These forms agree well with the available data and illuminate the dynamical content of $P$ and $Q$ .

NUCLEAR REACTIONS Closed form eikonal amplitude for spin dependent $p$ -nucleus scattering. Data-to-data forms relating spin observables to elastic scattering.

Polarization in intermediate energy inelastic scattering

J. A. McNeil and D. A. Sparrow

Phys. Rev. C 23, 2124 (1981) - Published 1 May, 1981

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The simple relationship between the elastic polarization and elastic cross section derived previously is generalized to include inelastic processes. The resulting data-to-data relations express the inelastic polarization in terms of the corresponding unpolarized scattering distribution and two spin "lengths" related to the relative strength and range of the spin orbit to central fundamental amplitudes. The success of these relations in describing inelastic analyzing powers indicates that little new nuclear structure information can easily be obtained from such experiments.

NUCLEAR REACTIONS Intermediate energy inelastic polarization, data-to-data relationship between polarization and unpolarized angular distribution.

Calculation of spallation yields: Application to the spallation of lanthanum induced by 600 MeV protons

G. Rudstam and E. Hagebø

Phys. Rev. C 23, 2129 (1981) - Published 1 May, 1981

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The cascade-evaporation model of spallation reactions has been used for a theoretical calculation of the yields of cesium isotopes produced in the irradiation of a thick lanthanum target with 600 MeV protons. The results are compared to experimental data. The experimental isotopic yield distribution is well reproduced except for the very neutron-deficient part where the theoretical model underestimates the yields.

NUCLEAR REACTIONS Spallation ${}^{139}{La} (p, spall)$ , $E = 600$ MeV; calculated formation yields of Cs isotopes.

Pion-nucleus optical potential in the isobar-doorway model

A. N. Saharia, R. M. Woloshyn, and L. S. Kisslinger

Phys. Rev. C 23, 2140 (1981) - Published 1 May, 1981

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The isobar-doorway model is used to parametrize the pion-nucleus optical potential so as to take into account the interaction of the $Δ$ with other nucleons as well as coupling to inelastic and reaction channels. The parameters of the model are determined by fitting elastic scattering angular distributions. It is found that the nonlocality associated with the isobar propagation is important in the resonance energy region. This may indicate that the use of impulse approximation in obtaining the pion optical potential may be doubtful even if we introduce a complex shift in the energy at which the pion-nucleon scattering amplitude is evaluated to get a first-order optical potential.

NUCLEAR REACTIONS Pion-nucleus optical potential, parametrization of many-body modifications to the isobar propagator, $σ (θ)$ and $σ$ for ${}^{16}O$ , ${}^{12}C$ , and ${}^{4}{He}$ in the energy range 110-250 MeV.

Absence of $J^{π}$ , $T = 0^{+}, 1$ level excitations in residual nuclei from ( $π^{\pm}, 2 N$ ) reactions

C. E. Stronach, B. J. Lieb, H. O. Funsten, W. J. Kossler, H. S. Plendl, and V. G. Lind

Phys. Rev. C 23, 2150 (1981) - Published 1 May, 1981

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Gamma-ray spectra taken in prompt coincidence with incident 180-MeV $π^{+}$ , 220-MeV $π^{-}$ , and 0-MeV $π^{-}$ on the self-conjugate targets ${}^{12}C$ and ${}^{32}S$ show that the cross sections/yields are equal to or near zero for production of the $J^{π}$ , $T = 0^{+}, 1$ levels of the odd $Z$ , odd $N$ nuclei resulting from $np$ removal. The 0-MeV $π^{-}$ results can be explained by selection rules governing one-step quasifree interactions, but the $Δ (1232)$ region results cannot. This suggests that there may be additional restrictions upon the pion absorption mechanism.

NUCLEAR REACTIONS ${}^{12}C (π^{\pm}, X γ) {}^{10}B$ , ${}^{32}S (π^{\pm}, X γ) {}^{30}P$ ; $E_{π^{-}} = 0 MeV, 220 MeV$ ; $E_{π^{+}} = 180$ MeV; detected $γ$ rays, Ge(Li); measured $E_{γ}$ , 90° $σ$ and $Y$ (%) for $np$ removal; deduced reaction mechanism.

Self-consistent $π N t$ matrix

J. W. Van Orden, M. K. Banerjee, D. M. Schneider, and S. J. Wallace

Phys. Rev. C 23, 2157 (1981) - Published 1 May, 1981

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The $π N$ interaction in the nuclear medium is shown to be substantially altered by local field effects, including dressing of internal pion lines by the optical potential. The local field effect arises due to scattering of pions in the intermediate states of the $π N t$ matrix from other nucleons in the medium. We develop an organization of pion scattering theory based on Goldstone diagrams which includes all possible contributions but emphasizes the dressing of propagators in $π N t$ -matrix intermediate states involving one pion and one nucleon only. Pion absorption and rescattering are treated on an equal footing. Self-consistency is introduced through the demand that the optical potential which dresses internal propagators be the same as the optical potential which is implied by the $t$ matrix so corrected. For calculational purposes, the general theory is simplified to the case of the $π N t$ matrix in a Fermi gas. The input data consist of the free $π N t$ matrix, an off-shell form factor, the $π N$ coupling constant, a binding energy, and a Fermi momentum $k_{F}$ . Nucleon recoil effects are retained, as they have previously been found to be important. Numerical results are presented for the quantity $W (k, ω)$ which is related to the Klein-Gordon optical potential for nuclear matter. The results show substantial modification of the $π N$ resonance by the nuclear medium. In particular, the resonance is broadened and the treatment of pion absorption provides sensible results for the imaginary part of the self-energy near threshold. Our calculations show the self-consistency is not crucial to the results, as dressing of propagators by the first-order optical potential is adequate. Nucleon recoil is significant. The results show that local field effects are important in $π$ -nucleus interactions.

NUCLEAR REACTIONS General $π$ -nucleus scattering theory, self-consistent $π N t$ matrix, absorption, nucleon recoil, Pauli effects, propagator dressing, optical potential.

True absorption and scattering of pions on nuclei

D. Ashery, I. Navon, G. Azuelos, H. K. Walter, H. J. Pfeiffer, and F. W. Schlepütz

Phys. Rev. C 23, 2173 (1981) - Published 1 May, 1981

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The cross section for true absorption of pions in nuclei was obtained from experiments at 85, 125, 165, 205, 245, and 315 MeV for positive pions and at 125 and 165 MeV for negative pions. The results are compared with theoretical calculations. The inclusive pion scattering angular distribution was also measured, and the results indicate that quasifree scattering plays an important role for backward scattering. The total pion-nucleus cross section is decomposed into its major channels: elastic scattering, inclusive inelastic scattering, true absorption, and single charge exchange, as a function of pion energy and charge. For light nuclei, the true absorption cross section has a strong energy dependence, reflecting the shape of the (3,3) resonance. The $A$ dependence of the true absorption cross section is much stronger than that of the inclusive inelastic scattering.

NUCLEAR REACTIONS Li, C, Al, Fe, Nb, Bi ( $π^{\pm}, π^{'}$ ); measured $σ (θ_{π^{'}})$ , $E_{π^{+}} = 85, 125, 165, 205, 245, and 315$ MeV, $E_{π^{-}} = 125, 165$ MeV; deduced $σ_{inelastic}$ , $σ_{absorption}$ ; decomposition of $σ_{tot}$ .

Two-step processes in intermediate energy hadron-nucleus scattering

R. D. Amado, J. A. McNeil, and D. A. Sparrow

Phys. Rev. C 23, 2186 (1981) - Published 1 May, 1981

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We obtain closed form approximate expressions for two-step hadron nucleus excitations. These are cast in the form of data-to-data relations of elastic and inelastic scattering, which in turn allow prediction of one- versus two-step dominance given prior knowledge of the electromagnetic rates. The data-to-data relations also lead to a simple envelope test for determining what number of steps is dominant in a given region of momentum transfer. Besides giving these qualitative results, the data-to-data forms give an excellent quantitative description of the data.

NUCLEAR REACTIONS Closed form eikonal amplitude for two-step excitation processes. Data-to-data relations of elastic and inelastic scattering. Phase rules and envelope tests.

$s$ -wave repulsion in the pion-nucleus optical potential and the subthreshold pion-nucleon $T$ matrix

R. S. Bhalerao and C. M. Shakin

Phys. Rev. C 23, 2198 (1981) - Published 1 May, 1981

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A covariant theory of the pion-nucleus interaction has been used to calculate off-shell matrix elements of the first-order pion-nucleus optical potential in momentum space. The matrix elements $〈 k | v_{l} (W) | k 〉$ are calculated for ${}^{16}O$ and ${}^{40}{Ca}$ , as a function of $k$ , the momentum in the $π$ -nucleus center-of-mass system, for $W = m_{π} + M_{N}$ . (As in our previous studies we have carried out a full integration over the Fermi motion of the target nucleons. Off-shell effects related to nuclear binding are treated carefully.) As this calculation is sensitively dependent upon the subthreshold $π N T$ matrix, two different models for the $T$ matrix are studied. One is the well known separable model of Londergan, McVoy, and Moniz. The second model includes terms describing the direct and crossed Born terms and therefore has the appropriate $s$ - and $u$ -channel nucleon poles. (In the calculations using this model both the pion and the nucleon are allowed to go off the mass shell.) The remaining part of the amplitude in the second model is represented by a separable form. For small $k$ , the matrix elements of the optical potential calculated with these two models are significantly larger than those obtained when use is made of the fixed-scatterer approximation. Phenomenological optical potentials which describe low-energy pion-nucleus scattering data or pionic-atom data exhibit $s$ -wave repulsion which is about 2-8 times that obtained from calculations made in the fixed-scatterer approximation. (The uncertainty in this enhancement factor reflects the uncertainty in the free-space values of the $π N$ scattering lengths). We conclude that the explanation of a significant fraction of the $s$ -wave repulsion in the low energy pion-nucleus interaction may lie in a careful treatment of off-shell effects using a good model for the subthreshold $π N T$ matrix.

NUCLEAR REACTIONS Pion-nucleus interactions, off-shell effects in the pion-nucleus interaction at low energy; pionic atoms.

Anomalous nuclear enhancement in large transverse momentum hadron production

Masashi Wakamatsu

Phys. Rev. C 23, 2203 (1981) - Published 1 May, 1981

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The anomalous nuclear enhancement of inclusive spectra at large transverse momentum in high energy protonnucleus collisions is investigated in the framework of the nuclear parton model, especially by taking account of the interaction between the partons of the incident proton and the "collective" partons of the multiquark clusters within the nucleus. The absolute normalization of the parton distribution functions for the multiquark clusters is treated carefully, guided by the quark number and momentum sum rules.

NUCLEAR REACTIONS $Be (p, π^{\pm}) X$ , $Ti (p, π^{\pm}) X$ , $W (p, π^{\pm}) X$ , $E_{P}^{lab} = 400$ GeV. Nuclear parton models; hard scattering models; large $p_{T}$ reactions; pion productions; multiquark clusters.

Beta decay of ${}^{21}O$

D. E. Alburger, C. J. Lister, J. W. Olness, and D. J. Millener

Phys. Rev. C 23, 2217 (1981) - Published 1 May, 1981

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The radioisotope ${}^{21}O$ was produced in the ${}^{9}{Be} ({}^{18}O, 2 p α) {}^{21}O$ reaction using 80-110-MeV ${}^{18}O$ ions. Activities emerging from a Be target foil were stopped in a He gas cell and transferred to a counting area where $γ$ and $β$ rays were measured using Ge(Li) and plastic detectors. Thirteen $γ$ rays were observed in singles, $γ - γ$ , or $β - γ$ coincidence measurements following the $β$ decay of ${}^{21}O$ to known excited states of ${}^{21}F$ at 1730, 3460, 3518, (3639), 4572, and 4584 keV. Detailed information on the properties of the ${}^{21}F$ energy levels was obtained. By stopping the gas flow and measuring the decay of $γ$ rays, the half-life of ${}^{21}O$ was found to be 3.42 ± 0.10 sec. $β$ end-point energies measured by $β - γ$ coincidences lead to a mass excess of 8105 ± 175 keV for ${}^{21}O$ in agreement with more accurate reaction $Q$ values. Detailed shell-model calculations were carried out and reproduce the main features of the ${}^{21}O$ decay scheme.

RADIOACTIVITY ${}^{21}O$ : measured $E_{γ}$ , $I_{γ}$ , $E_{β}$ , $I_{β}$ , $γ - γ$ , and $β - γ$ coin., $T_{\frac{1}{2}}$ ; gas transfer, Ge(Li) and plastic detectors; deduced ${}^{21}O$ decay, scheme, $log ft$ values; compared with theory.

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Skyrme-force time-dependent Hartree-Fock calculations with axial symmetry

Fusion excitation functions for ${}^{16}O$ + ${}^{27}{Al}$ and ${}^{16}O$ + ${}^{24}{Mg}$ collisions

Possible triaxial structures in ${}^{24}{Mg}$ from ${}^{16}O$ + ${}^{24}{Mg}$ elastic and inelastic scattering

Lifetime of the 1.04 MeV state in ${}^{18}F$ , measured through the inverse reaction ${}^{3}{He} ({}^{16}O, p) {}^{18}F$

High spin states in ${}^{156}{Yb}$ ( $N = 86$ )

Band structure in ${}^{80}{Kr}$

Nonequilibrium aspects in relativistic nuclear collisions

Comparison of ${}^{252}{Cf}$ spontaneous fission with ${}^{250}{Cf} (t, p f)$

Kinetic energy and fragment mass distributions for ${}^{240}{Pu}$ (s.f.), ${}^{239}{Pu} (n_{th}, f)$ , and ${}^{240}{Pu} (γ, f)$

Spin dependence in intermediate energy $p$ -nucleus scattering

Polarization in intermediate energy inelastic scattering

Calculation of spallation yields: Application to the spallation of lanthanum induced by 600 MeV protons

Pion-nucleus optical potential in the isobar-doorway model

Absence of $J^{π}$ , $T = 0^{+}, 1$ level excitations in residual nuclei from ( $π^{\pm}, 2 N$ ) reactions

Self-consistent $π N t$ matrix

True absorption and scattering of pions on nuclei

Two-step processes in intermediate energy hadron-nucleus scattering

$s$ -wave repulsion in the pion-nucleus optical potential and the subthreshold pion-nucleon $T$ matrix

Anomalous nuclear enhancement in large transverse momentum hadron production

Beta decay of ${}^{21}O$

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