Experimental total beta-decay energies of neutron-rich silver and cadmium isotopes are presented. The sources have been produced as mass-separated fission products by means of the on-line—isotope-separator technique. Beta spectra have been recorded in coincidence with different gamma transitions, and $Q_{\beta }$ values for ${}_{}{}^{116-121}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{119}{}_{}{}^{}\mathrm{Cd}$, and ${}_{}{}^{121}{}_{}{}^{}\mathrm{Cd}$ have been deduced. The atomic mass excess is derived for these nuclei, and comparisons are made with mass formula predictions.

RADIOACTIVITY ${}_{}{}^{116-121}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{119,121}{}_{}{}^{}\mathrm{Cd}$. Measured coincident beta spectra, deduced total beta-decay energies, atomic mass excesses; comparison with mass formulas. Mass-separated fission products. Si(Li) detectors, Ge(Li) detectors.

In a reinvestigation of the $\beta$ decay of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$, formed in the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(t, p){}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$ reaction at $E_t=3.0\mathrm{}$ MeV, the unique first-forbidden $\beta$-ray transition to the 4445 keV, $J^{\pi }={\frac{5}{2}}^{-}$ state of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ has been found with a branching intensity of 0.054±0.004% and $log{f}_{1}t=10.93\mathrm{}\pm 0.03$. The previously unobserved 692-keV $\gamma$-ray branch in the 7978→7286→0 cascade following the $\beta$ feeding of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ 7978-keV state has also been measured as 0.85% and limits were placed on other $\gamma$ branches from the 7978-keV level. Revised values are given for various other $\beta$- and $\gamma$-ray branching ratios. Shell model calculations are made using the full $1\hslash \omega$ basis for the positive-parity states and $0\hslash \omega +2\mathrm{}\hslash \omega$ for the negative-parity states. The calculated electromagnetic decays of positive-parity states in ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ are compared with experiment. The first-forbidden $\beta$-decay matrix elements involved in the decay of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$ to the lowest four states of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ are calculated and the resultant decay rates are compared with experiment. The question of meson exchange corrections to the ${\mathrm{½}}^{+}$ → ${\mathrm{½}}^{-}$ $\beta$ decay is considered.

RADIOACTIVITY ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$ [from ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(t, p)$]: measured $E_{\gamma }$, $I_{\gamma }$, $\gamma -\gamma$ coincidence; Ge(Li) and NaI(T1) detectors: deduced $\beta$- and $\gamma$-ray branches, $log\mathrm{ft}$ values; compared with theory.

A study of the $\beta -\nu$ angular correlation in the first-forbidden decay of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$ to the ${\mathrm{½}}^{-}$ 2125-keV level of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ was performed. The 2125-keV ground-state transition was detected in coincidence with the betas and at 180° to them. The $\beta -\nu$ asymmetry was deduced from the $\gamma$-ray Doppler shift. The result obtained as a function of $\beta$ energy indicates that the $\beta$ transition is dominated by rank 0 matrix elements and is thus of interest as a test of meson-exchange effects in nuclei. A comparison is made to the large-basis, spurious-free, shell-model predictions of Millener.

RADIOACTIVITY ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$ from ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(t, p)$: $\beta -\gamma$ coin.; plastic and Ge(Li) detectors, measured $\gamma$-ray Doppler shift: deduced $\beta -\nu$ asymmetry and rank 0 and 1 contributions to decay to ${\mathrm{½}}^{-}$ state, compared to theory.

The $\gamma$ radiation following the decay of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ to ${}_{}{}^{144}{}_{}{}^{}\mathrm{La}$ was measured with a variety of detectors in experiments where $\gamma$-ray singles, time dependent $\gamma$-ray spectra, $\gamma \gamma t$ coincidence, and $\gamma \gamma t$ angular correlation data were collected. The ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ activity was produced by on-line mass separation from the products of the ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n, f)$ reaction. The half-life of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ was determined to be 11.5±0.2 s. A level scheme for odd-odd ${}_{}{}^{144}{}_{}{}^{}\mathrm{La}$ was deduced from coincidence information in which 91 $\gamma$ rays were placed among 26 levels. Internal conversion and angular correlation measurements yielded spin-parity assignments for several levels. Several features of the level scheme are discussed including the $\beta$ decay to low-lying levels and the possible core-coupled structure of the $1^{+}$ levels.

RADIOACTIVITY ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ [from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n_{\mathrm{th}}, f)$], measured $t_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, ${\alpha }_K$, $\gamma \gamma$ coincidence, $\gamma \gamma \left(\theta \right)$ angular correlation; HPGe, Ge(Li), and LEPS detectors; ${}_{}{}^{144}{}_{}{}^{}\mathrm{La}$ deduced levels, $J^{\pi }$, $I_{\beta }$, $\delta$, and $log\mathrm{ft}$. Mass-separated ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ activity.

The decay of mass-separated ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$ produced in thermal neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ was studied by x-ray and $\gamma$-ray spectroscopy. The level scheme deduced for the $N=85\mathrm{}$ isotone ${}_{}{}^{141}{}_{}{}^{}\mathrm{Ba}$ differs substantially from previous level schemes. A new ${\frac{7}{2}}^{-}$ level at 55.0 keV was established as the second-excited state, completing the triplet of low-lying ${\frac{3}{2}}^{-}$, ${\frac{5}{2}}^{-}$, and ${\frac{7}{2}}^{-}$ states expected for this "quasi-$f_{\frac{7}{2}}$" nucleus. For transitions among these levels, values of $\left|\delta \right|\left(\frac{E2\mathrm{}}{M1\mathrm{}}\right)$ were deduced. Comparisons are made with level structures of other $N=85\mathrm{}$ isotones. Systematic trends in energies of states characteristic of quasi-$f_{\frac{7}{2}}$ nuclei are discussed.

RADIOACTIVITY ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$ [from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}(n, f)$]; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma$ coin., HpGe and Ge(Li) detectors; ${}_{}{}^{141}{}_{}{}^{}\mathrm{Ba}$ deduced levels, $J$, $\pi$, $log\mathrm{ft}$, $\left|\delta \right|\left(\frac{E2\mathrm{}}{M1\mathrm{}}\right)$. Mass-separated ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$ activity.

Large mesonic exchange current corrections are obtained in the calculation of the rate of muon capture by the deuteron with outgoing neutrinos of very small momentum. Detailed results are given for $m_{\nu }=0\mathrm{}$. No difference sufficiently large to be observed with present techniques is predicted for $m_{\nu }\le 2.5$ MeV/${\mathit{c}}^2$.

RADIOACTIVITY Muon capture ${}_{}{}^2{}_{}{}^{}\mathrm{H}+{\mu }^{-}\to n+n+{\nu }_{\mu }$, mesonic exchange contribution, small neutrino momentum.

A two-parameter pseudospin Hamiltonian is introduced which contains both the Meshkov-Glick-Lipkin and the Abecasis-Fässler-Plastino Hamiltonians as special cases. The ground state critical properties of the two-parameter Hamiltonian are determined: It exhibits both first and second order phase transitions. The ground state critical properties of any one-parameter pseudospin Hamiltonian contained in the two-parameter model can immediately be determined by inspecting the interaction parameter space of the two-parameter model. The critical set in this space is identified with that of the cusp catastrophe.

NUCLEAR STRUCTURE Pseudospin Hamiltonian, critical properties, first and second order phase transitions.

Empirical data from single-particle transfer reactions on the stable members of $T=\frac{1}{2}$ mirror pairs in the $2s-1d$ shell are analyzed using sum rules to obtain information about the expectation values of neutron and proton angular momenta, and spins of states in neighboring nuclei. The analysis provides estimates of the renormalization required for the various data sets, and of the errors in relative spectroscopic strengths. The angular momentum expectation values are compared with values calculated from measured magnetic moments and $\beta$-decay $\mathrm{ft}$ values, and used in an attempt to deduce information concerning exchange-current corrections to nucleon $g$ factors and the $\beta$-decay axial vector coupling constant. For mirror pairs with only one measured magnetic moment, the particle transfer data are used to predict the unknown moment. Occupation numbers for the $d_{\frac{5}{2}}$, $s_{\frac{1}{2}}$, and $d_{\frac{3}{2}}$ subshells are deduced from the renormalized data sets.

NUCLEAR STRUCTURE $T=\frac{1}{2}$ mirror nuclei, $2s-1d$ shell, sum rule analysis, single particle transfer data. Calculated proton, neutron $J$; $\mu$, $\mathrm{ft}$ value; exchange current corrections. Calculated proton, neutron $J$; $J^{\pi }$; occupation numbers; unmeasured $\mu$.

A possible excitation scheme of particle-hole states in $N\ne Z$ nuclei is worked out within the isospin formalism. Particle-hole states with a definite isospin are decomposed into 1p-1h (particle-hole), 2p-2h, and 3p-3h states. This decomposition enables us to relate transition strengths from the ground state to the excited states and those in the adjacent nuclei. The same thing is done for $\Delta$ isobar-hole states. Using these results, we obtain the relations among the quenching strengths of magnetic transitions in $N\ne Z$ nuclei. In particular, we apply these relations to the $M1\mathrm{}$ states around ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and compare the results with experimental data obtained by ($p, n$), ($p, p^{\prime }$), and ($e, e^{\prime }$) experiments on ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$.

NUCLEAR STRUCTURE Isospins, $\Delta$ isobar polarization.

The potential energy $V$ is taken as the unperturbed Hamiltonian and the kinetic energy $K$ is used as the perturbation. As $K$ is a semipositive definite operator, one may use standard Padé approximants to reconstruct the Brillouin-Wigner functional. It is shown that, while the bare projector ${\mathrm{}(E-V)\mathrm{}}^{-1\mathrm{}}$ is plagued in the complex $E$ plane by the cut which results for the continuous spectrum of $V$, one may nonetheless solve the Brillouin-Wigner equation in a limit from the complex plane to the real axis. The theory is illustrated by a numerical example.

NUCLEAR STRUCTURE Brillouin-Wigner perturbation theory, strong coupling, Padé approximants.

Within the framework of the Blankenbeckler-Sugar equations the effects of one-loop corrections to the driving force are studied in the two-nucleon system. In particular, contributions from the direct and crossed box two-pion exchange diagrams are calculated. An analysis is made at the one-loop level for both pseudoscalar and pseudovector pion-nucleon coupling using a geometric unitarization. In a model with one boson exchanges it is shown that the agreement between the Bethe-Salpeter and the quasipotential results does not improve in all partial waves when the one-loop contributions are included. Various qualitative fits to the experimental data are presented for such a model.

NUCLEAR REACTIONS $\mathrm{NN}$ system, quasipotential equations compared with the Bethe-Salpeter equations. Method to calculate one-loop contributions. Comparison of pseudovector and pseudoscalar pion-nucleon coupling at the one-loop level.

A ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ shell-model formalism, including two- and three-body forces, is used to calculate ground and first excited state properties. Inclusion of the three-body force improves the calculated ground state rms radius, ground state form factor, and position of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ first excited state.

NUCLEAR STRUCTURE Calculated the influence of three-body forces on the position of the ground state rms radius, ground state form factor, and position of the first excited state in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. Three-body forces lead to significant improvements in the aforementioned properties.

Energy spectra of $\alpha$-particles were measured at 0° for the systems ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}$ in the range $E_{\mathrm{lab}}\left({}_{}{}^{28}{}_{}{}^{}\mathrm{Si}\right)=75-102\mathrm{}$ MeV in 0.750 MeV steps. Transitions to discrete states in ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ up to ∼20 MeV excitation energy via the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{28}{}_{}{}^{}\mathrm{Si}, \alpha ){}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ reaction are observed. The excitation functions measured for some of these transitions show structures ∼1 MeV wide. No strong (${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, $\alpha$) transitions to discrete states are observed for the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ system.

NUCLEAR REACTIONS ${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}({}_{}{}^{28}{}_{}{}^{}\mathrm{Si}, \alpha )$, $E=75-102\mathrm{}$ MeV, measured $\sigma \mathrm{}\left(E\right)\mathrm{}$, ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ deduced levels.

The elastic scattering cross section for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ has been measured in the range ${\theta }_{\mathrm{lab}}=1.5-9\mathrm{}°$. Evidence for a nuclear rainbow effect is reported. A value of the reaction cross section is deduced from the optical model analysis.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ elastic scattering, $E_{\mathrm{lab}}=1016\mathrm{}$ MeV, optical model analysis, deduced nuclear rainbow angle, reaction cross section.

The half-life of the ${\frac{3}{2}}^{+}$, 724.3-keV level in ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$, populated in the decay of ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$, has been determined to be 3.2±0.8 nsec. The observed lifetime and $\gamma$-ray branching supports the interpretation that the rotational band structure in the odd-mass Ag isotopes arises from the $g_{\frac{7}{2}}$ shell-model state.

RADIOACTIVITY ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$; measured $\gamma -\gamma$, $\beta -\gamma$ delayed coin., $T_{\frac{1}{2}}$ of 724.3-keV level; enriched targets; Ge(Li), Ge(HP), and NE-111 plastic-scintillation detectors.

Spectra of 37.2 and 60.6 MeV electrons scattered at 180° constitute evidence for very low observable $M1\mathrm{}$ transition strength and significant $M2\mathrm{}$ transition strength in the 9 MeV excitation energy region of ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$. This is consistent with recent high resolution results of other workers at more forward angles.

NUCLEAR REACTIONS ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(e, e^{\prime })$, $E_0=37.2, 60.6$ 60.6 MeV; measured $\frac{d\sigma }{d\Omega }$ at $\theta =180\mathrm{}°$.

Differential cross sections for elastic scattering of 13.9 MeV ${\pi }^{+}$ from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ have been measured for $30°<{\theta }_{\mathrm{lab}}<150\mathrm{}°$. The data agree well with coordinate space optical potential calculations.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({\pi }^{+}, {\pi }^{+}){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. $E_{{\pi }_{\mathrm{lab}}}=13.9\mathrm{}$ MeV $30°<{\theta }_{\mathrm{lab}}<150\mathrm{}°$, comparison with coordinate space optical potential calculations.

The levels up to 1135 keV in ${}_{}{}^{109}{}_{}{}^{}\mathrm{Cd}$ were excited via ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}(p, n\gamma )$ reaction. For the first time, the lifetimes of energy levels at 673, 721, 821, 891, 997, 1106, and 1135 keV have been measured using Doppler shift attenuation technique.

NUCLEAR REACTION ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}(p, n\gamma )$, $E_p=3.4\mathrm{} \mathrm{and} 3.9$ MeV; measured lifetime; DSA technique.

Differential cross sections at ${\theta }_{\pi }=90\mathrm{}°$ (lab) for ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\gamma , {\pi }^{+}){}_{}{}^9{}_{}{}^{}\mathrm{Li}(\mathrm{g}.\mathrm{s}.\mathrm{})$ at $T_{\pi }=17, 29, \mathrm{and} 42$ MeV were measured. Results are compared to other data and to Helm model calculations.

NUCLEAR REACTIONS ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\gamma , {\pi }^{+}){}_{}{}^9{}_{}{}^{}\mathrm{Li}(\mathrm{g}.\mathrm{s}.\mathrm{})$, $E_{\gamma }=175, 187, \mathrm{and} 200$ MeV; measured $\sigma ({\theta }_{\pi }=90\mathrm{}°)$, DWIA Helm model calculations.

A new activity, $T_{\frac{1}{2}}=20\mathrm{}\pm 2$ sec, was observed in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ bombardments of ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$. Only one $\gamma$ ray, 476.0±0.1 keV, was found to be associated with this nuclide. We identify the new isotope as ${}_{}{}^{150}{}_{}{}^{}\mathrm{Er}$ and propose that it decays mainly to one level in ${}_{}{}^{150}{}_{}{}^{}\mathrm{Ho}$ at an excitation energy of ∼476 keV by an allowed $\beta$ transition which connects states with the following configurations: $0^{+}(\pi h_{\frac{11}{2}}, \pi h_{\frac{11}{2}})\to 1^{+}(\pi h_{\frac{11}{2}}, \nu h_{\frac{9}{2}})$. As part of the investigation, the decay properties of the high- and low-spin ${}_{}{}^{150}{}_{}{}^{}\mathrm{Ho}$ isomers were reexamined.

RADIOACTIVITY ${}_{}{}^{150}{}_{}{}^{}\mathrm{Er}$, ${}_{}{}^{150}{}_{}{}^{}\mathrm{Ho}$ measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma$ coincidence; ${}_{}{}^{150}{}_{}{}^{}\mathrm{Ho}$, ${}_{}{}^{150}{}_{}{}^{}\mathrm{Dy}$ deduced levels, $J^{\pi }$.