Decay of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Np}$ ($T_{\frac{1}{2}}=13.9\mathrm{}\pm 0.2$ min) was studied by $\gamma$-ray spectroscopy. The Np sources, prepared by the ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ ($\alpha$,$p$) and ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$($n$,$p3n$) reactions, were chemically separated and purified. Eleven $\gamma$ rays, mostly new, were observed between 42.0 and 929.7 keV, and their intensities per disintegration were determined. A decay scheme for ${}_{}{}^{241}{}_{}{}^{}\mathrm{Np}$ is proposed which helps to elucidate the level structure of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$. Comparison with nuclear reaction data is used to identify a $\frac{5}{2^{-}}$ octupole vibrational state and to characterize some of the other levels.

RADIOACTIVITY 13.9-min ${}_{}{}^{241}{}_{}{}^{}\mathrm{Np}$ from ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$($\alpha$,$p$) and ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$($n$,$p3n$); radiochemistry, Ge(Li) and $4\pi \beta$ detectors. Measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$; radiochemistry, Ge(Li) and $4\pi \beta$ detectors. Measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$; deduced $I_{{\beta }^{-}}$, $log\mathrm{ft}$, $I^{\pi }$, decay scheme.

Mass separated radioactive sources of ${}_{}{}^{192}{}_{}{}^{}\mathrm{Tl}$ and ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pb}$ were produced using an isotope separator connected on-line to a cyclotron. Gamma-ray multiscale spectra and electron singles spectra were acquired and $\gamma -\gamma$ and (x-ray)-$\gamma$ coincidence measurements made. Half-lives of the $2^{-}$ and $7^{+}$ thallium isomers were determined to be 9.4±0.2 and 10.8±0.3 min, respectively. The $7^{+}$ isomer decays primarily to a group of negative-parity states built upon a $5^{-}$ state at 1843.9 keV in ${}_{}{}^{192}{}_{}{}^{}\mathrm{Hg}$. This structure has been interpreted as a two-neutron band involving $i_{\frac{13}{2}}$ and low-$j$ neutrons. The decay of the $2^{-}$ isomer populates the low-lying positive-parity states in ${}_{}{}^{192}{}_{}{}^{}\mathrm{Hg}$ in addition to a number of states in the region of 1-2.5 MeV; the properties of the six lowest positive-parity states are compatible with the triaxial-rotor predictions for $\gamma \sim 37°$, a value which also reproduces the structure of bands in adjacent odd-$A$ nuclei. The ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pb}$ decay to ${}_{}{}^{192}{}_{}{}^{}\mathrm{Tl}$ is found to have a half-life of 3.5 ± 0.1 min, rather than 2.2 min as reported by previous investigators. Most of the ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pb}$ decay proceeds to levels at 167.5 and 1195.4 keV, assigned ${\mathrm{I}}^{\pi }=1^{-} \mathrm{and} 1^{+}$, respectively. The systematic variation of the $1^{+}$ state in even-$A$ Tl and Au nuclei is discussed in light of the trend of the $h_{\frac{11}{2}}$ proton state in odd-$A$ Tl and Au isotopes.

RADIOACTIVITY ${}_{}{}^{192}{}_{}{}^{}\mathrm{Tl}$, ${}_{}{}^{192}{}_{}{}^{}\mathrm{Tl}_{}^m{}_{}{}^{}$, ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pb}$ [from Ta, $W({}_{}{}^{16}{}_{}{}^{}\mathrm{O},xn)$, $E=100, 133, 143$ MeV]; mass separated sources; measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $E_{\mathrm{ce}}$, $I_{\gamma }$, $I_{\mathrm{ce}}$, $\gamma -\gamma$ coin, ICC; ${}_{}{}^{192}{}_{}{}^{}\mathrm{Hg}$, ${}_{}{}^{192}{}_{}{}^{}\mathrm{Tl}$ deduced levels, $J$, $\pi$, multipolarities, $log\mathrm{ft}$.

Energy dependence of the $\frac{1}{2^{-}}\left(693\mathrm{} \mathrm{keV} \beta \right)\frac{3}{2^{+}}\left(342\mathrm{} \mathrm{keV} \gamma \right)\frac{1}{2^{+}}$ angular correlation was measured with a fast-slow scintillation spectrometer. The data was used in conjunction with the other available experimental observables to determine the beta matrix elements, employing Buhring's formalism as modified by Simms. The sizes of the matrix elements indicate a "cancellation effect." It was observed that the vector matrix element ratio ${\Lambda }_{\mathrm{CVC}}$ was consistent with the conserved vector current prediction based on the fact that the Coulomb Hamiltonian is diagonal. However, contributions from off-diagonal matrix elements of the Coulomb Hamiltonian could not be rules out. The structure of the involved levels is discussed on the basis of the single particle shell model and the one-quasiparticle-phonon coupling model.

RADIOACTIVITY ${}_{}{}^{111}{}_{}{}^{}\mathrm{Ag}$; measured $\beta \gamma \left(\theta \right)$, deduced nuclear matrix elements.

Best possible bounds on expectation values of the energy-averaged Bloch-Horowitz effective Hamiltonian are derived, assuming knowledge of only moments $m_0,\dots ,m_n$ of the intermediate-state Hamiltonian. These bounds are independent of the presence of intruder states. The simplest case that leads to nontrivial bounds is $n=2\mathrm{}$. Explicit formulas are given for the $n=2\mathrm{}$ upper and lower bounds for the Lorentzian averaging width $\Gamma$. There exists an intermediate range of $\Gamma$ values, within which the bounds depend weakly on $\Gamma$. For $n=2\mathrm{}$, the intermediate $\Gamma$ values are of the order of the width of the strength function of the intermediate-state excitation. For larger $n$, the intermediate $\Gamma$ values decrease, permitting finer resolution at the price of increased computation. A universal graph is given to aid in estimating the effect of Bloch-Horowitz self-consistency on the $n=2\mathrm{}$ bounds. For a low-lying state with moments typical of those suggested by statistical spectroscopic theory, the upper and lower bounds differ from their average by about 25% of the virtual excitation contribution. Finally, an iterative method for approximating the model-space wave function is described.

NUCLEAR STRUCTURE Energy averaged effective interactions, Lorentzian averaging. Moments, best possible bounds, inclusion region, moment cone, bounding polynomial, self-consistency.

Three three-nucleon model problems are proposed as test cases for numerical computation: the ground and excited states of a spin-isospin independent Yukawa potential (Delves potential) and the ground state of a spin-isospin independent potential composed of one attractive and one repulsive Yukawa function (Malfliet-Tjon V). Eigenvalues and eigenfunctions are calculated using a configuration space Faddeev approach, and variational upper and lower bounds are evaluated using these wave functions. Each calculation is performed both as a projected $s$-wave potential problem, and as a true local potential problem in which nucleon-nucleon partial waves through $l=6\mathrm{}$ are kept. For each case the eigenvalue appears to be converged to within 1 keV and it agrees well with the upper bound. A brief review of bounding techniques is presented.

NUCLEAR STRUCTURE Variational bounds, three-body problem.

Starting with the previous result that the equation of motion for some collective motion of the nuclear fluid can be approximated by the Lamé equation, we consider the nuclear giant resonances as elastic vibrations of a nucleus, the properties of elasticity being a peculiar manifestation of the quantum stress tensor. The nucleus is taken to be compresible and endowed with elastic moduli, surface tension, Coulombic charge, and two-body viscosity. Eigenenergies and widths for the isoscalar electric multipole states ($0^{+}$,$1^{-}$,$2^{+}$,$3^{-}$,$4^{+}$,...) and the isoscalar magnetic multipoles states ($1^{+}$,$2^{-}$,$3^{+}$,$4^{-}$,...) are obtained. The energies and widths of the $0^{+}$,$2^{+}$, and $3^{-}$ states agree well with those of the observed giant resonances. Such agreement lends support to the present macroscopic description of the collective excitation of a nucleus. Nuclear viscosity coefficients and the incompressibility of nuclear matter are extracted. In the present unified approach, the high-lying electric multipole "giant resonance" states and the low-lying "liquid-drop" states emerge as eigenstates of the same characteristic equation. Similarities and differences between these two types of states are assessed.

NUCLEAR STRUCTURE Giant resonances vibration of a compressible, elastic sphere with surface tension, charge, and viscosity. Electric multipole and magnetic multipole resonances. Nuclear viscosity coefficients and incompressibility extracted.

A procedure for constructing a collective Hamiltonian for a given nuclear collective motion is developed from the generator coordinate method. The procedure is based on the construction of a collective subspace of the many-body Hilbert space, and this is achieved by the diagonalization of the generator coordinate method overlap kernel. The Weyl transformation makes the connection between nonlocal phase space Hamiltonian kernels, obtained from the generator coordinate method, and operators in the collective space. The Gaussian overlap approximation and monopole vibrations in light spherical nuclei are studied in this formalism.

NUCLEAR STRUCTURE Generator coordinate method. Weyl transformation. Collective Hamiltonians. Application to the monopole giant resonance.

Experiments concerning gamma-ray emission after thermal-neutron capture by oriented nuclei have been reconsidered in order to show that information on the multipole character of the statistical gamma-ray spectra in ($n$,$\gamma$) reactions can be obtained. It is found that, for the ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}$ and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Sm}$ compound nuclei, these spectra have mainly dipole character. An upper limit of about 10% quadrupole is deduced.

NUCLEAR REACTIONS ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$($n$,$\gamma$), ${}_{}{}^{149}{}_{}{}^{}\mathrm{Sm}$($n$,$\gamma$), $E_n$ thermal; dipole nature of statistical $\gamma$ spectra.

Results from a study of the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ ($t$,$\alpha$) reaction with 17-MeV polarized tritons, as well as an analysis of earlier results, lead to an assignment of $J^{\pi }=4^{+}$ for ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$* (6.53).

NUCLEAR REACTIONS ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ ($t$,$\alpha$), $E(\mathrm{pol}.\mathrm{})=17\mathrm{}$ MeV, measured $\sigma \left(\theta \right)$, $A_y$ for $\alpha$ group to ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$*(6.53). Analysis by CCBA leads to $J^{\pi }$.

The unusual energy distribution of $\alpha$ particles emitted in the reaction ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$($n$,$\alpha$) ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$ at incident energies 12-18 MeV, is explained as being due to the shell structure of ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$ in the hypothesis that the mechanism responsible for $\alpha$ emission is the knockon by the incident neutron of $\alpha$ particles preformed in the target nucleus. The same interpretation is offered to describe the spectrum of $\alpha$ particles in the reaction ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$($p$,$\alpha$) ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$.

NUCLEAR REACTIONS ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$($n$,$\alpha$) ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$, $E=12-18\mathrm{}$ MeV; measured $\sigma (E_{\alpha },E_n)$ and $\sigma (E_{\alpha },\theta )$. Discussed influence of shell structure of ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$ on the measured spectrum.

A search has been made for $\gamma$ rays emitted following the electron-capture and/or ${\beta }^{-}$ decay of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}$. No excess of counts above background was observed in the vicinity of any of the expected $\gamma$-ray energies. From these results, lower limits on the partial half-lives of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}$ against electron-capture and ${\beta }^{-}$ decay have been determined to be ≥5.6×${10}^{13}$ and ≥5.6×${10}^{13}$ yr, respectively.

RADIOACTIVITY ${}_{}{}^{180}{}_{}{}^{}\mathrm{Ta}$: measured $I_{\gamma }$; deduced lower limits for $T_{\frac{1}{2}}$, $log\mathrm{ft}$. Enriched source, Ge(Li) detectors.

Half-lives of some levels in ${}_{}{}^{131}{}_{}{}^{}\mathrm{Xe}$ have been measured by the delayed coincidence method. Analysis of the data by the slope method gave the following values: 416±20 ps, 1.34±0.04 ns, 67.5±1.4 ps, and <75 ps for the 80.2-341.1-, 364.5-, and 404.8-keV levels, respectively.

RADIOACTIVITY ${}_{}{}^{131}{}_{}{}^{}\mathrm{I}$[from ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}(n,\gamma ){}_{}{}^{131}{}_{}{}^{}\mathrm{Te}\stackrel{{\beta }^{-}}{\to }$]; measured $\beta \gamma \mathrm{}\left(t\right)\mathrm{}$, $\gamma \gamma \mathrm{}\left(t\right)\mathrm{}$; deduced ${}_{}{}^{131}{}_{}{}^{}\mathrm{Xe}$ level $T_{\frac{1}{2}}$.

The ${}_{}{}^{198}{}_{}{}^{}\mathrm{Pt}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$→${}_{}{}^{211}{}_{}{}^{}\mathrm{Po}$+$\gamma$ heavy-ion radiative capture reaction was investigated at 60 and 57 MeV bombarding energies using a rabbit system to search for delayed $\alpha$ particles from the $T_{\frac{1}{2}}=25.5\mathrm{}$ s isomeric state in ${}_{}{}^{211}{}_{}{}^{}\mathrm{Po}$. A cross section $\sigma \lesssim 1$ nb is reported for the total radiative capture cross section averaged over the center of mass energy range $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}\sim 49-54$ MeV. This result is consistent with statistical model calculations.

NUCLEAR REACTIONS ${}_{}{}^{198}{}_{}{}^{}\mathrm{Pt}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, $E=57-60\mathrm{}$ MeV; measured upper limit for radiative capture cross section to $T_{\frac{1}{2}}=25.5\mathrm{}$ s isomeric state in ${}_{}{}^{211}{}_{}{}^{}\mathrm{Po}$; calculated cross sections. Enriched targets. Si surface barrier detector.

Branching ratios for the lepton-violating ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(${\mu }^{-}$,$e^{+}$)${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$(g.s.) reaction are calculated using a gauge model in which it is mediated by a Majorana neutrino. The predicted branching ratios to the ground state are fairly insensitive to the relevant nuclear structure information and are much smaller than previously calculated total rates.

NUCLEAR REACTIONS ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ (${\mu }^{-}$,$e^{+}$)${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$(g.s.); calculated branching ratio. Lepton conversion.

We construct a complex energy functional to be used in the calculation of the nucleus-nucleus optical potential. The functional is related to a Skyrme-like nucleon-nucleon interaction derived from a finite range complex interaction previously obtained from nuclear matter calculations appropriate to heavy ion collisions. Calculations for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ reproduce very well the results obtained from the finite range interaction.

NUCLEAR REACTIONS Heavy ion optical potential from a complex energy functional approach.

Realistic wave functions are used to calculate threshold ${\pi }^{+}$ photoproduction from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in the impulse approximation. The effects of the $D$-state components, the Coulomb interaction in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and the nuclear size on this cross section are investigated. In particular, it is argued that since realistic forces underbind and produce too large a radius, such model calculations should be expected to give (approximately 10%) too small a cross section. The resulting theoretical estimate is in reasonable agreement with experimental data.

NUCLEAR REACTIONS Three-body problem, photopion reactions, threshold effects.

The role played by the $1g_{\frac{9}{2}}$ orbital vis-á-vis the structure of the recently observed high-spin yrast cascade in ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ is examined. The anomalous high-spin sequence is correctly reproduced. A number of electromagnetic transitions are predicted.

NUCLEAR STRUCTURE High-spin yrast levels in ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$: calculated energies, electromagnetic properties. Shell-model calculations in the ($p_{\frac{3}{2}}$,$p_{\frac{1}{2}}$,$f_{\frac{5}{2}}$,$g_{\frac{9}{2}}$) space.

The effect of coupling of the two-phonon states on elastic and $2^{+}$ inelastic cross sections is calculated for 8 MeV neutrons incident on ${}_{}{}^{76,80,82}{}_{}{}^{}\mathrm{Se}$. Isospin optical parameters and deformation parameters are determined from comparison with data. The values of $\beta$ are larger than one would expect on the basis of measured values from ($p$,$p^{\prime }$) and Coulomb excitation.

NUCLEAR REACTIONS ${}_{}{}^{76,80,82}{}_{}{}^{}\mathrm{Se}$ ($n$,$n$) and ($n$,$n^{\prime }$); cross sections calculated with coupled channels; effects of two-phonon coupling.

The effect of center-of-mass correlations and a restriction of the set of intermediate nuclear states have been studied for pion scattering from the mass three system. Results indicate that, for the present, these effects can be ignored.

NUCLEAR REACTIONS ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\pi }^{\pm }$, ${\pi }^{\pm }$)${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\pi }^{-}$, ${\pi }^0$)${}_{}{}^3{}_{}{}^{}\mathrm{He}$, center-of-mass effects, nuclear correlations, intermediate states, nuclear structure information.

All the members of the $h_{\frac{11}{2}}$ rotational structure have been observed in ${}_{69}{}^{159}{}_{}{}^{}\mathrm{Tm}$ up to spin ${\frac{49}{2}}^{+}$. The alignments of these bands relative to the core nuclei ${}_{68}{}^{158}{}_{}{}^{}\mathrm{Er}_{90}^{}{}_{}{}^{}$ and ${}_{70}{}^{160}{}_{}{}^{}\mathrm{Yb}_{90}^{}{}_{}{}^{}$ are presented. These data provide additional evidence that the second backbend of the yrast structure of the core results from an ${\left(h_{\frac{11}{2}}\right)}^2$ proton alignment.

NUCLEAR REACTIONS ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$,$3n$)${}_{}{}^{159}{}_{}{}^{}\mathrm{Tm}$, $E=68\mathrm{}$ MeV; measured $\gamma -\gamma$ coin, $\gamma \left(\theta \right)$. ${}_{}{}^{159}{}_{}{}^{}\mathrm{Tm}$ deduced levels.