The solution of the Faddeev equations for the three-nucleon system with separable $s$-wave two-nucleon interactions has been continued onto the second sheet where resonance poles would appear if any existed. No resonance poles were found in the regions searched where previous work has suggested the possible existence of resonances. When the two-nucleon coupling constants are weakened slightly, a virtual state in the triton system becomes bound in the ${}_{}{}^2{}_{}{}^{}S$ channel. When the two-nucleon coupling constant is considerably strengthened new resonances appear in the three-nucleon system.

[NUCLEAR STRUCTURE Three-nucleon systems Faddeev solutions for separable $s$-wave interactions, continued onto second sheet. Two-nucleon coupling constants varied to study resonances.]

The decay widths for the $M1\mathrm{}$ and $E2\mathrm{}$ transitions in the $\gamma$ decay of the isobaric analog resonance of the ${}_{}{}^{63}{}_{}{}^{}\mathrm{Ni}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$ have been measured. The preferential excitation of a group of ${\frac{1}{2}}^{-}$ and ${\frac{3}{2}}^{-}$ states in these transitions with $\Delta T=1\mathrm{}$ can be directly related to the hindrance of the $\beta$ decay of ${}_{}{}^{63}{}_{}{}^{}\mathrm{Ni}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$. A detailed comparison with the predictions of the shell model shows the necessity of including excitations from the $1f_{\frac{7}{2}}$ shell in the calculation.

[NUCLEAR REACTIONS ${}_{}{}^{62}{}_{}{}^{}\mathrm{Ni}(p,\gamma )$, $E=2.48\mathrm{}$ MeV. ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$ levels measured $E_{\gamma }$ and ${\Gamma }_{\gamma }$; deduced $B\left(M1\mathrm{}\right)\mathrm{}$ and $B\left(E2\mathrm{}\right)\mathrm{}$. Enriched target, Ge(Li) detector, 3.0 keV at 1.3 MeV. Calculated $B\left(M1\mathrm{}\right)\mathrm{}$ and $B\left(E2\mathrm{}\right)\mathrm{}$. Shell model with Kuo matrix elements.]

The reaction ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(d,p\gamma ){}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ has been studied at a deuteron energy of 10 MeV up to an excitation energy in ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$ of 3.5 MeV. A multidetector arrangement consisting of eight silicon surface-barrier detectors has been used to measure the proton spectra. Particle-$\gamma$-coincidence measurements have been performed with a Ge(Li) detector in and perpendicular to the reaction plane. The angular distributions of the absolute double differential cross sections have been measured for particle angles between 30 and 150°. It turned out that the differential as well as the double differential cross section for transitions with an $l$ transfer of 0 or 1 can be described well by the distorted-wave Born-approximation (DWBA) method. DWBA fails to describe the angular correlations of the $l=2\mathrm{}$ transitions. The "$j$-forbidden" $l=4\mathrm{}$ transitions leading to the ${\frac{7}{2}}^{+}$ state at 1.611 MeV and ${\frac{9}{2}}^{+}$ state at 3.399 MeV have been compared with Hauser-Feshbach predictions. While the differential cross section of the transition to the ${\frac{7}{2}}^{+}$ state is compatible with Hauser-Feshbach calculations, the double differential cross sections for both transitions cannot be described by Hauser-Feshbach theory. Potential ambiguities, arising from DWBA analyses of the differential cross sections could not be removed from the analyses of the double differential cross sections.

[NUCLEAR REACTIONS ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(d,p\gamma )$, $E=10\mathrm{}$ MeV; measured double differential cross sections. DWBA analyses of $l=0,1, \mathrm{and} 2$ transitions and Hauser-Fesh-bach analyses of $l=4\mathrm{}$ transitions; enriched target.

The $Q$ values for ($p,t$) reactions leading to ${}_{}{}^{22}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{30}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{34}{}_{}{}^{}\mathrm{Ar}$ have been measured, yielding mass excesses for these nuclei of -399 ± 3 keV, -713 ± 3 keV, -14 062 ± 3 keV, and -18 379 ± 3 keV, respectively. The results for ${}_{}{}^{22}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{34}{}_{}{}^{}\mathrm{Ar}$ are significantly different from average values quoted in the 1971 Mass Tables. For all four nuclei, these results allow the $\mathrm{ft}$ values for their Fermi $\beta$-decay branches to be calculated with improved precision, and in the cases of $A=26\mathrm{}$ and $A=34\mathrm{}$ more exacting comparisons of mirror Fermi decays become possible. The measured asymmetries now are $\Delta \mathrm{}\left(26\right)=-1.2\mathrm{}\pm 1.6\%$ and $\Delta \mathrm{}\left(34\right)=0.2\mathrm{}\pm 0.6\%$, thus removing any obvious disagreement with calculations of charge-dependent mixing.

[NUCLEAR REACTIONS ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}\mathrm{}(p,t)\mathrm{}$, $E=40.2\mathrm{}$ MeV; measured $Q$ values. ${}_{}{}^{22}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{30}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{34}{}_{}{}^{}\mathrm{Ar}$ deduced masses, $\mathrm{ft}$ values, mirror asymmetries for $A=26,34\mathrm{}$.]

The strong linear polarizations of the deexcitation $\gamma$ rays from the ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}({}_{}{}^{18}{}_{}{}^{}\mathrm{O},4n\gamma ){}_{}{}^{110}{}_{}{}^{}\mathrm{Cd}$ reaction at 60 MeV were measured using a Ge(Li) two-crystal Compton polarimeter. Previous experiments with this reaction resulted in the identification of a side band feeding into the known $4^{+}$ and $6^{+}$ states via two dipolar $\gamma$ rays from states with spins 5 and 7 and with energies of 996 and 399 keV, respectively. These two dipole transitions were found to be $E1\mathrm{}$. Several other known quadrupole transitions were found to be $E2\mathrm{}$. Thus we assign odd parity to the levels at 2538 keV ($5^{-}$), 2878 keV ($7^{-}$), and 3344 keV ($9^{-}$). The feasibility of such measurements with this polarimeter is discussed.

[NUCLEAR REACTIONS ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}({}_{}{}^{18}{}_{}{}^{}\mathrm{O},4n\gamma )$, $E=60\mathrm{}$ MeV; enriched ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$ target. Linear polarizations of ${}_{}{}^{110}{}_{}{}^{}\mathrm{Cd} \gamma$ rays measured.]

A Ge(Li)-Ge(Li) directional-correlation system has been utilized to measure the (740-40-141), (740-181), and the previously unreported (740-40) and (40-141) correlations. The multipole mixing ratios obtained were $\delta \mathrm{}\left(740\right)=3.58\mathrm{}\pm 0.20$, $\delta \mathrm{}\left(40\right)=-0.008\mathrm{}\pm 0.008$, $\delta \mathrm{}\left(141\right)=-0.118\mathrm{}\pm 0.006$, and $\delta \mathrm{}\left(181\right)=0.002\mathrm{}\pm 0.007$. The first three mixing ratios are $\frac{E2\mathrm{}}{M1\mathrm{}}$ and the last one is $\frac{M3\mathrm{}}{E2\mathrm{}}$. In addition the spin assignment of $\frac{3}{2}$ for the 921-keV level has been confirmed.

[RADIOACTIVITY ${}_{}{}^{99}{}_{}{}^{}\mathrm{Mo}$ [from ${}_{}{}^{96}{}_{}{}^{}\mathrm{Mo}(n,\gamma )$]; measured $\gamma -\gamma \left(\Theta \right)$. ${}_{}{}^{99}{}_{}{}^{}\mathrm{Tc}$ deduced $J$, $\gamma$ mixing. Ge(Li) detectors.]

Strong triton peaks in the ($p,t$) spectra on the lead isotopes with $E_p=51.9\mathrm{}$ MeV were observed. Assignments of $6^{+}$ (or an $L=6\mathrm{}$ transfer) were made from comparisons with distortedwave Born-approximation predictions assuming a ${({2f}_{\frac{5}{2}},{2f}_{\frac{7}{2}})}^{-1\mathrm{}}$ two-hole state as their main configuration. Further, a pronounced peak was found near $E_x=5\mathrm{}$ MeV at relatively large scattering angles in both the ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}\mathrm{}(p,t)\mathrm{}{}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}\mathrm{}(p,t)\mathrm{}{}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ reactions. Assignment of an $L=11\mathrm{}$ transfer which corresponds to an ${\left[{(h_{\frac{9}{2}},i_{\frac{13}{2}})}^{-1\mathrm{}}\right]}_{{11}^{-}}$ two-hole state in the residual nucleus was made for such states.

[NUCLEAR REACTIONS ${}_{}{}^{208,207,206,204}{}_{}{}^{}\mathrm{Pb}\mathrm{}(p,t)\mathrm{}$, $E=51.9\mathrm{}$ MeV; measured $\sigma (E;\theta )$; ${}_{}{}^{206,204,202}{}_{}{}^{}\mathrm{Pb}$ deduced systematic $6^{+}$, ${11}^{-}$ states. Enriched targets, DWBA analysis, resolution 100 keV; $\theta =6-{65}^{\circ }$.]

A coupled-channel-Born-approximation (CCBA) study is made of ($p,t$) reactions leading to two-phonon states of vibrational nuclei. A detailed numerical analysis is performed, particularly for the ${}_{}{}^{116}{}_{}{}^{}\mathrm{Cd}\mathrm{}(p,t)\mathrm{} {}_{}{}^{114}{}_{}{}^{}\mathrm{Cd}$ reaction with the incident energy $E_p=28\mathrm{}$ MeV. It is shown that many features observed in the reactions, which cannot be explained by the distorted-wave Born approximation (DWBA), can successfully be accounted for by CCBA. It is also shown that three-step processes play an essential role in the successful explanation of the observed data, particularly the cross sections of the $0^{+}$ and $4^{+}$ two-phonon states.

[NUCLEAR REACTIONS ${}_{}{}^{116}{}_{}{}^{}\mathrm{Cd}\mathrm{}(p,t)\mathrm{}$, $E=28\mathrm{}$ MeV; calculated $\sigma \left(\Theta \right)$.]

Using the National Bureau of Standards electron linac and underground time-of-flight facility, precise average neutron-transmission measurements have been made in the energy range $1 \mathrm{keV}\le E\le 600 \mathrm{keV}$ on the elements As, Br, Nb, Rh, Ag, In, Sb, I, La, Ho, Au, and Th. The samples were "thick" in that the $s$-wave self-protection had to be accounted for at low energies. However, the samples were still sufficiently thin that any errors introduced by neglecting $p$-wave self-protection were negligible. The average $R$-matrix theory was employed in the analysis and the $l=0\mathrm{}$ scattering length $R^{\prime }$ and the $p$-wave strength function $S_1$ were extracted from the data. The behavior of $S_1$ vs mass number $A$ in the region of the $3P$ maximum was found to vary smoothly with no evidence of any splitting of the resonance. Using Moldauer's optical potential, which fits the $l=0\mathrm{}$ data well, the behavior of $S_1$ vs $A$ was calculated. The predicted behavior was found to differ significantly from experiment. In particular, experiment indicates $S_1$ peaks at a lower mass number and that the maximum is stronger than indicated by the calculations. When the constants of the potential were changed in order to reproduce the observed behavior of $S_1$, a significant discrepancy with the $l=0\mathrm{}$ data resulted. The results presented here imply an orbital angular momentum dependence of the low-energy optical potential.

[NUCLEAR REACTIONS As, Br, Nb, Rh, Ag, In, Sb, I, La, Ho, Au, Th; measured average neutron transmission $E=1-600\mathrm{}$ keV; deduced $R^{\prime }$, $p$-wave strength function; optical-model analysis.]

The $\beta$ and subsequent $\gamma$ decays of ${}_{}{}^{138}{}_{}{}^{}\mathrm{Xe}$ and ${}_{}{}^{138}{}_{}{}^{}\mathrm{Cs}$ were investigated using the on-line isotope separator system TRISTAN at the Ames Laboratory research reactor. Ge(Li) $\gamma$-ray singles and Ge(Li)-Ge(Li) $\gamma -\gamma$ coincidence measurements were used to construct level schemes for ${}_{}{}^{138}{}_{}{}^{}\mathrm{Cs}$ and ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$. For the decay of ${}_{}{}^{138}{}_{}{}^{}\mathrm{Xe}$, 94 of 99 observed $\gamma$-ray transitions have been placed in a level scheme for ${}_{}{}^{138}{}_{}{}^{}\mathrm{Cs}$ with 27 excited states. For the decay of ${}_{}{}^{138}{}_{}{}^{}\mathrm{Cs}$, 82 of 86 observed $\gamma$ rays are placed in a level scheme for ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$ with 35 excited states. Ge(Li)-plastic coincidence measurements gave $Q$ values of 2.83 ± 0.08 MeV and 5.29 ± 0.07 MeV for ${}_{}{}^{138}{}_{}{}^{}\mathrm{Xe}$ and ${}_{}{}^{138}{}_{}{}^{}\mathrm{Cs}$, respectively. Spin and parity assignments have been deduced using $\gamma$-ray transition rates, $\beta$-decay $log\mathrm{ft}$ values, and other information existing in the literature. Interpretation of some of the energy levels is made from a shell-model viewpoint.

Level schemes for ${}_{}{}^{91}{}_{}{}^{}\mathrm{Rb}$ and ${}_{}{}^{91}{}_{}{}^{}\mathrm{Sr}$ are proposed based on the study of the $\beta$ decay of ${}_{}{}^{91}{}_{}{}^{}\mathrm{Kr}$ and ${}_{}{}^{91}{}_{}{}^{}\mathrm{Rb}$, respectively. The samples were obtained using on-line mass-separation techniques applied to ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ fission products. $\gamma$-, $\beta$-, and x-ray singles spectra, as well as ($\gamma ,\gamma$) and ($\beta ,\gamma$) coincidence spectra, were taken with Ge(Li) and Si(Li) detectors. Internal-conversion coefficients were determined for several transitions and the half-lives for the first two levels in ${}_{}{}^{91}{}_{}{}^{}\mathrm{Rb}$ and ${}_{}{}^{91}{}_{}{}^{}\mathrm{Sr}$ were measured. In view of the observed parity change between low-lying excited states and the ground state in ${}_{}{}^{91}{}_{}{}^{}\mathrm{Rb}$ the possibility of deformations to explain this level structure is discussed.

High-resolution Ge(Li) detectors have been used to observe $\gamma$-ray singles and coincidence spectra of 2.2-h ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sn}$ (${\frac{11}{2}}^{-}$ ground state). Sources of mixed tin isotopes were produced by thermal-neutron fission of enriched ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and were chemically separated by solvent extraction and sulfide precipitation. A total of 162 $\gamma$ rays are attributed to the decay of ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sn}_{}^g{}_{}{}^{}$, and 154 of these transitions have been placed in a ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sb}$ level scheme involving 50 excited states. The $\beta$ feeding from ${\frac{11}{2}}^{-}{}_{}{}^{127}{}_{}{}^{}\mathrm{Sn}_{}^g{}_{}{}^{}$ to the ${\frac{7}{2}}^{+}$ ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sb}$ ground state was determined to be (22 ± 8)% ($logft=8.0\mathrm{}$). Spin and parity assignments for ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sb}$ levels have been made in many instances. An 11 ± 1-μsec ${\frac{15}{2}}^{-}$ isomeric level in ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sb}$ at 1920 keV has been identified. The level structure of ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sb}$ is interpreted in terms of the shell model and core-excitation considerations.

[RADIOACTIVITY ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sn}_{}^g{}_{}{}^{}$ (from ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ fission); measured $E_{\gamma }$, $I_{\gamma }$, $t_{\frac{1}{2}}\gamma$, $\gamma -\gamma$ coin; deduced $E_{\beta }$, $I_{\beta }$, $log\mathrm{ft}$. ${}_{}{}^{127}{}_{}{}^{}\mathrm{Sb}$ deduced levels, $J$, $\pi$. Enriched target; Ge(Li) detectors.]

The mean life of the 77.3-keV level in ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ has been measured simultaneously in neutral gold atoms and in atoms with a mean charge of $\overline{q}=+9.5\mathrm{}\pm 1.5$. Mean lives of ${\tau }^0=2.76\mathrm{}\pm 0.03$ nsec and ${\tau }^{+9.5\mathrm{}}=2.84\mathrm{}\pm 0.12$ nsec were obtained. These results indicate that even the removal of 10 electrons from this atom does not affect the electronic structure of the inner shells, and therefore has little effect on the internal-conversion coefficients and lifetime of this nuclear state. These results are in good agreement with both relativistic and nonrelativistic calculations.

[RADIOACTIVITY ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$; $E_x=77.3\mathrm{}$ keV, measured $T_{\frac{1}{2}}$ in neutral and ionized atoms, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$′), $E=45\mathrm{}$ MeV, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}-\gamma$ delayed coin; calculated ICC.]

$\gamma -\gamma$ directional correlation and polarization directional correlation experiments were performed on three cascades in ${}_{}{}^{96}{}_{}{}^{}\mathrm{Mo}$ populated from ${}_{}{}^{96}{}_{}{}^{}\mathrm{Tc}$ (4.3 day). Ge(Li) detectors were used in both spectrometers. Combination of the results give unique spin-$4^{+}$ assignment to the 1628-keV level and spin-$6^{+}$ assignments to both the 2441- and 2755-keV levels in ${}_{}{}^{96}{}_{}{}^{}\mathrm{Mo}$.

[RADIOACTIVITY ${}_{}{}^{96}{}_{}{}^{}\mathrm{Tc}$ [from ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}(\alpha ,n)$]; measured $\gamma \gamma \left(\theta \right)$ and $\gamma \gamma$ (90° LP) (linear polarization correlation). ${}_{}{}^{96}{}_{}{}^{}\mathrm{Mo}$ deduced $I$. Ge(Li) detectors.]

The $K$-shell and $L$-subshell internal-conversion coefficients of the retarded transitions in ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}$ populated in the decay of the 6.8-day ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}$ have been measured using a high-resolution double-focusing electron spectrometer and a 20-${\mathrm{cm}}^3$ Ge(Li) detector. The $K$ conversion coefficients of the 71.6- and 113-keV transitions have been determined by $\gamma -\gamma$ and $\gamma$-x-ray coincidence measurements using a 1-${\mathrm{cm}}^3$ Ge(Li) detector having a thin window and a scintillation detector. The $\gamma -\gamma$, $\gamma -e^K$, and $e^K-\gamma$ angular correlations of the 208.3-113-keV cascade have been measured using a single gap electron spectrometer, NaI(Tl) $\gamma$-ray spectrometers, and a Ge(Li) detector. The particle parameters for the $K$ conversion electrons of the transitions have been evaluated to be: $b_2^K$ (208.3) = -1.54 ± 0.06 and $b_2^K$ (113) = -0.20 ± 0.02. The 208.3-113-keV $\gamma -\gamma$ angular correlation as measured using a Lu${\mathrm{Cl}}_3$ source in solution gave $W\left(\theta \right)=1-(0.192\mathrm{}\pm 0.007)P_2\left(cos\theta \right)$. The quadrupole admixtures and the penetration parameters of the transitions were evaluated by least-squares analysis of the conversion coefficients and particle parameters. The best solutions are $Q=(3.1\mathrm{}\pm 1.6)\%$, ${\lambda }_1=-19.2\mathrm{}\pm 1.2$, ${\lambda }_2=250\mathrm{}\pm 240$ for the 321.3-keV transition; $Q<\mathrm{}0.2\%$, ${\lambda }_1=-0.8\mathrm{}\pm 0.9$, ${\lambda }_2=0\mathrm{}$ for the 208.3-keV transition; $Q=(0.03\mathrm{}\pm 0.02)\%$, ${\lambda }_1=1.3\mathrm{}\pm 0.8$ for the 71.6-keV transition; $Q=(94.1\mathrm{}\pm 0.7)\%$, $\lambda =5.6\mathrm{}\pm 8.4$ for the 113-keV transition, and $Q=(95\mathrm{}\pm 5)\%$ for the 136.7-keV transition. From these values and the known lifetimes of the levels the $\gamma$-ray matrix elements and the penetration matrix elements have been calculated and compared with theoretical estimates based on Nilsson's model.

[RADIOACTIVITY ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}$; measured $I_{\gamma }$, $I_{\mathrm{ce}}$, $\mathrm{x}\gamma$ and $\gamma \gamma$ coin, $\gamma \gamma \left(\theta \right)$, $\mathrm{ce} \gamma \left(\theta \right)$. ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}$, deduced ICC, $b_2^K$, $\delta$, penetration parameters. Double focusing and single gap $e$ spectrometers, Ge(Li) detectors. Enriched target.]

Ground-state radiation widths (${\Gamma }_{\gamma 0}$) for 36 $p_{\frac{3}{2}}$ photoneutron resonances in ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$ have been measured from 5-225 keV above threshold at the Argonne National Laboratory threshold photoneutron facility. Reduced neutron widths (${{\gamma }_n}^2$) for the same resonances were obtained at the Oak Ridge Electron Linear Accelerator facility from total-cross-section measurements on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$. A strong correlation ($\rho =+0.59\mathrm{}$) is observed between the two sets of widths. Because of a lack of knowledge of the relative phase of the compound-nucleus and valence amplitudes in the individual resonances, the average valence component cannot be deduced from the correlation analysis. However, one can obtain a mean compound-nucleus contribution by studying those resonances where the valence amplitude is expected to be negligible. By using such a procedure, an average valence component is obtained which is in excellent agreement with the average valence strength calculated from the valence model. The $s$-wave neutron strength function is $S^0=(6.2\mathrm{}\pm 1.2)\times {10}^{-5\mathrm{}}$ and the $p$-wave strength function is $S^1$ = (3.2 ± 0.8) × ${10}^{-4\mathrm{}}$. The reduced photon width for $E1\mathrm{}$ transitions is $\overline{k}\mathrm{}\left(E1\mathrm{}\right)=(3.2\mathrm{}\pm 0.6)\times {10}^{-3\mathrm{}}$, in agreement with the single-particle reduced width derived from the Weisskopf model. The neutron widths are observed to follow a Porter-Thomas distribution, while the photon widths appear to follow a ${\chi }^2$ distribution with two degrees of freedom.

[NUCLEAR REACTIONS ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}(\gamma ,n)$, $E_{\gamma }=9.0\mathrm{}$ MeV; deduced ${\Gamma }_{\gamma 0}$ of resonances. ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$($n$, total), $E_n=5-225\mathrm{}$ keV; measured $\sigma \mathrm{}\left(E\right)\mathrm{}$, deduced ${{\gamma }_n}^2$ of resonances. Determined correlation, calculated valence contribution to ${\Gamma }_{\gamma 0}$; calculated strength functions.]

Two-proton quasiparticle states in ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ have been studied with (${}_{}{}^3{}_{}{}^{}\mathrm{He},d$) and ($\alpha ,t$) reactions on ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$. Rotational bands built upon quasiparticle states formed by the [$523\uparrow$] proton state coupled with the [$411\downarrow$], [$404\downarrow$], and [$541\downarrow$] proton states were identified. For each rotational band, the cross sections have a characteristic pattern which has been used to identify the band. Assignments were checked by comparing the ratios of (${}_{}{}^3{}_{}{}^{}\mathrm{He},d$) and ($\alpha ,t$) cross sections for each level.

[NUCLEAR REACTIONS ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}({}_{}{}^3{}_{}{}^{}\mathrm{He},d){}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$, $E=35.6\mathrm{}$ MeV, ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}(\alpha ,t){}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$, $E=46\mathrm{}$ MeV; measured $\sigma (E_d,\theta )$ and $\sigma (E_t,\theta )$; ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ deduced levels, $J$, $\pi$.]

The level scheme of ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$ has been studied by thermal and resonance neutron capture. The low-energy region has been measured with the high-resolution bent-crystal spectrometer at Risø, Denmark. The medium- and high-energy $\gamma$ rays, coincidence spectra, and $\gamma -\gamma$ angular correlations were measured at the Brookhaven National Laboratory (BNL) high flux beam reactor. Primary transitions from resonance capture in ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ were studied with the fast chopper facility at BNL. Out of ∼520 observed transitions, ∼330 were placed in a level scheme containing 60 levels below 3.3 MeV. Many of these states are new and a great number of new $I^{\pi }$ assignments was made. In particular $I^{\pi }=0^{+}$ was assigned to a level at 1515 keV. Four $1^{-}$ states between 2.4 and 3 MeV are suggested. Possible explanations of their low excitation energy are offered. The simplest require and therefore suggest oblate shapes in ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$, at least for excitations involving the unique parity orbitals. A very systematic behavior of the level feeding by nonprimary transitions was found in this nucleus and was compared to simple statistical predictions. A detailed comparison was made with model calculations for core-coupled proton states. The most likely candidates for these states are: $2_1^{+}$ 368 keV, $2_2^{+}$ 1254 keV, $2_3^{+}$ 1573 keV, $0_2^{+}$ 1515 keV, $1_1^{+}$ 1570 keV, $3_1^{+}$ 1659 keV. The possibility of a reduced central density of ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$ is discussed.

[NUCLEAR REACTIONS ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}(n,\gamma )$, $E=\mathrm{thermal},33.5,129.7,\mathrm{and} 175.1$ eV measured $I_{\gamma }$, $\gamma -\gamma \mathrm{coin}\left(\theta \right)$ in ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$. ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$ deduced levels, transitions, $J$, $\pi$, ICC, multipolarities, $\delta$.]

The recoil distance method was used to measure the lifetime of the $J^{\pi }=4^{+}$ second excited state of ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ at 3.555-MeV excitation, which was formed via the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}\mathrm{}(t,p)\mathrm{}{}_{}{}^{18}{}_{}{}^{}\mathrm{O}_{}^{*}{}_{}{}^{}$ reaction at $E_t=3.1\mathrm{}$ MeV. The mean life is found to be $\tau =46.2\mathrm{}\pm 3$ psec, which corresponds to an $E2\mathrm{}$ strength for the 3.55 ($4^{+}$→ 1.98 ($2^{+}$) transition of ${\mathrm{}\left|M\right(E2\mathrm{}\left)\right|}^2=0.64\mathrm{}\pm 0.05$ Weisskopf units. This result is in good agreement with the predictions of recent theoretical calculations in the weak-coupling model, which identifies the lowest-lying $2^{+}$ and $4^{+}$ states as predominantly 2p-0h states based on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. The predictions of this model for mirror states ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$ are discussed. Additional data were obtained coincidentally for states of ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ formed via the competing ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}\mathrm{}(t,n)\mathrm{}{}_{}{}^{18}{}_{}{}^{}\mathrm{F}_{}^{*}{}_{}{}^{}$ reaction. The results, which are in good agreement with previous values, are: 0.937-MeV state, $\tau =65.4\mathrm{}\pm 5.3$ psec and for the 1.081-MeV state, $\tau =26.1\mathrm{}\pm 2.3$ psec.

Using a counter telescope assembly, the fission $\alpha$-particle spectrum associated with the spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ was remeasured. No evidence was seen for any large number of short-range fission $\alpha$ particles emitted at the instant of scission. The shape of the $\alpha$-particle energy spectrum is quasi-Gaussian but shows more low-energy particles than would be predicted by a Gaussian shape. The shape of the $\alpha$-particle energy spectrum and angular distribution are well described by a simple three-point charge-trajectory calculation. The parameters resulting from this calculation indicate that the fission fragments are well separated (∼23 fm) and possess significant kinetic energies (heavy-fragment kinetic energy of 25 MeV) at the moment of appearance of the $\alpha$ particle.