The low-lying structure of the odd-odd nuclei ${}_{}{}^{30}{}_{}{}^{}\mathrm{P}$ and ${}_{}{}^{34}{}_{}{}^{}\mathrm{Cl}$ is studied in a modified version of the vibrational unified model in which anharmonic and quasiparticle effects are included. The results are compared with recent shell-model calculations and yield satisfactory agreement with recently observed level schemes and decay rates.

The ($d,d^{\prime }n$) reaction has been studied in ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ and other targets, using 19-MeV deuterons. Deuteron angular distributions and yields indicate that the ($d,d^{\prime }$) reaction is predominantly direct at forward angles, but probably has a large compound-nuclear component at backward angles, and observed angular correlations for $d^{\prime }-n$ coincidences indicate that the neutrons are mainly products of evaporation from a ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ compound nucleus. The fractional yield, $F_n=\frac{{\Gamma }_n}{\Gamma }$, for neutron emission is found to be substantially below unity for ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ excitation energies $E_i$ extending to several MeV above the neutron binding energy $B_n$ (e.g., $F_n\simeq 0.75$ at $E_i-B_n=2\mathrm{}$ MeV), indicating the importance of competition from $\gamma$-ray emission. For $E_i-B_n<3\mathrm{}$ MeV, $F_n$ is independent of deuteron angle and its magnitude can be accounted for in terms of the statistical model. Because the relative neutron and $\gamma$-ray emission widths are strongly dependent on the ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ spin population, this lack of dependence of $F_n$ on deuteron detection angle suggests that the ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ spin population is similar for direct and compound-nuclear ($d,d^{\prime }$) reactions. For $E_i-B_n>3\mathrm{}$ MeV, the value of $F_n$ at forward deuteron angles is anomalously low. Results are also presented for the ($d,d^{\prime }n$) reaction in ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$.

Isobaric-analog resonances have been observed in proton elastic scattering from ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ at proton energies from 4.76 to 10.10 MeV. The observed resonances in ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$ are identified as analogs of low-lying states of ${}_{}{}^{87}{}_{}{}^{}\mathrm{Kr}$. The data have been analyzed using a shell-model description of isobaric-analog resonances. Orbital-angular-momentum-transfer values, resonance energies, total and partial widths, and spectroscopic factors for 14 of the observed resonances are presented. The results are shown to be in good over-all agreement with ($d,p$) studies on the target nucleus.

The level structure of the ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$-${}_{}{}^{87}{}_{}{}^{}\mathrm{Kr}$ system has been investigated by means of the inelastic scattering of protons through isobaric-analog resonances (IAR's). 24 levels in ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ between 1.55 and 5.07 MeV have been identified in the spectra. Excitation-function data indicate that coupling of the $d_{\frac{5}{2}}$ single particle to excited states of ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ provides important contributions to the wave function of the IAR's. The coefficients describing the coupling of single-particle states to the excited core states in ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ were extracted from the angular-distribution measurements of the inelastic proton decay of the 5.348-, 6.826-, and 8.374-MeV IAR's. The inclusion of these coefficents together with previously deduced elastic spectroscopic factors allows a rather full description of the wave functions for the parent analog states of these IAR's. A calculation of the wave functions and binding energies in terms of a simple core-coupling model has been performed for the $d$ and $s$ states in ${}_{}{}^{87}{}_{}{}^{}\mathrm{Kr}$. The calculation shows good agreement with the results of the analysis of the proton decay of the IAR for the low-lying states.

The mean lifetime of a number of levels of the ground-state band in ${}_{}{}^{120,122}{}_{}{}^{}\mathrm{Xe}$ and the first $2^{+}$ states in ${}_{}{}^{126,128}{}_{}{}^{}\mathrm{Ba}$ have been measured with the recoil-distance Doppler-shift method. The nuclei were produced by (${}_{}{}^{16}{}_{}{}^{}\mathrm{O},4n$) reactions. The measured $E2\mathrm{}$ transition strengths which range from 50 to 100 Weisskopf units support the assumption of a transitional character for this neutron-deficient region. The deduced deformation parameters are found to be in rather good agreement with the predictions of theoretical calculations and the phenomenological variable-moment-of-inertia model.

The parity-violating forward-backward asymmetry of the 57-keV $\gamma$ radiation from low-temperature polarized ${}_{}{}^{180m}{}_{}{}^{}\mathrm{Hf}$ has been measured to be -(19.4 ± 9.2) × ${10}^{-4\mathrm{}}$, indicating the lack of any large parity-violating effect for this very strongly hindered $E1\mathrm{}$ transition, in agreement with our calculations. The $\frac{M2\mathrm{}}{E1\mathrm{}}$ and $\frac{E3\mathrm{}}{E1\mathrm{}}$ multipole mixing ratios of the 57-keV transition have been determined to be ${\delta }_1\left(\frac{M2\mathrm{}}{E1\mathrm{}}\right)=-\left({0.009}_{-0.085\mathrm{}}^{+0.065\mathrm{}}\right)$ and ${\delta }_2\left(\frac{E3\mathrm{}}{E1\mathrm{}}\right)=+0.013\mathrm{}\pm 0.020$.

For many nuclei the isobaric analog of the target ground state excited in the $X(p,n)Y$ charge-exchange reaction decays by the emission of a single proton ($\tilde{p}$) group. In this paper a relation is established for the angular dependence of the centroid energy, $〈E_{\tilde{p}}\left(\theta \right)〉$, for this $\tilde{p}$ group. The measurement of $〈E_{\tilde{p}}\left(\theta \right)〉$ determines the average momentum along the beam direction, $〈P_{\mathrm{rz}}〉$, given the recoiling nucleus $Y$ in the ($p,n$) charge-exchange reaction. The value for $〈P_{\mathrm{rz}}〉$ determines the cross-section weighted average value of $cos{\theta }_n$ for the ($p,n$) angular distribution $\frac{d\sigma }{d\Omega }\left({\theta }_n\right)$; and thus provides a qualitative characterization of the ($p,n$) angular distribution. $〈E_{\tilde{p}}\left(\theta \right)〉$ was measured for the ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}(p,n\tilde{p})$ process at 23.15 MeV; and a value for $〈P_{\mathrm{rz}}〉$ of 140 MeV/c was determined. The results of this experiment are compared with recent angular-distribution measurements of the ($p,n$) charge-exchange reaction on the tin isotopes at 23 MeV.

Investigations of the angular distribution of $\gamma$ radiation from ${}_{}{}^{239}{}_{}{}^{}\mathrm{Np}$ polarized at low temperatures in Zr${\mathrm{Fe}}_2$ have suggested small forward-backward asymmetries for several of the hindered $E1\mathrm{}$ and $M1\mathrm{}$ $\gamma$ transitions of ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$. From the anisotropies of the $\gamma$-ray angular distributions, the following multipole mixing ratios were deduced: $\frac{E2\mathrm{}}{M1\mathrm{}}:\delta \mathrm{}\left(210\right)=-0.02\mathrm{}\pm 0.02$, $\delta \mathrm{}\left(228\right)=-0.07\mathrm{}\pm 0.03$, $\delta \mathrm{}\left(254\right)=-0.12\mathrm{}\pm 0.06$, $\delta \mathrm{}\left(278\right)=+0.16\mathrm{}\pm 0.03$; $\frac{M2\mathrm{}}{E1\mathrm{}}:\delta \mathrm{}\left(106\right)=+0.05\mathrm{}\pm 0.03$, $\delta \mathrm{}\left(316\right)=-0.10\mathrm{}\pm 0.12$, $\delta \mathrm{}\left(334\right)=+0.02\mathrm{}\pm 0.03$. The small $\frac{E2\mathrm{}}{M1\mathrm{}}$ mixing ratios of the $\Delta K=2\mathrm{}$ transitions are explainable in terms of Coriolis mixing. The 512-keV level of ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ has been identified as the ${\frac{7}{2}}^{+}\mathrm{}\left[624\right]\mathrm{}$ Nilsson state, which assignment yields the $\frac{E2\mathrm{}}{M1\mathrm{}}$ mixing ratio $\delta \mathrm{}\left(182\right)=-0.12\mathrm{}\pm 0.08$. The hyperfine splitting of ${}_{}{}^{239}{}_{}{}^{}\mathrm{Np}$ in (${\mathrm{U}}_{0.005}$${\mathrm{Zr}}_{0.995}$)${\mathrm{Fe}}_2$ has been determined to be 60 ± 5 mK. Difficulties encountered in the selection of a suitable ferromagnetic environment for ${}_{}{}^{239}{}_{}{}^{}\mathrm{Np}$ are discussed. Spin assignments and $\gamma$-ray multipole mixing ratios in ${}_{}{}^{131,132,133}{}_{}{}^{}\mathrm{Xe}$ were deduced from angular distributions of $\gamma$ rays following the decays of fission products ${}_{}{}^{131,132,133}{}_{}{}^{}\mathrm{I}$.

Over 300 transitions up to 4.5 MeV in excitation energy were observed in the ($d,t$) and ($d,p$) reactions on ${}_{}{}^{204}{}_{}{}^{}\mathrm{Hg}$, ${}_{}{}^{202}{}_{}{}^{}\mathrm{Hg}$, ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$, and ${}_{}{}^{198}{}_{}{}^{}\mathrm{Hg}$ and in the ($d,d^{\prime }$) reaction on ${}_{}{}^{204}{}_{}{}^{}\mathrm{Hg}$, ${}_{}{}^{202}{}_{}{}^{}\mathrm{Hg}$, and ${}_{}{}^{201}{}_{}{}^{}\mathrm{Hg}$ at a bombarding energy of 17 MeV. All targets were isotopically enriched and out-going particles were detected in a split-pole spectrograph having 8- to 14-keV (full width at half maximum) resolution. Over 100 angular distributions in the ($d,p$) and ($d,t$) reactions were measured and compared with distorted-wave Born-approximation calculations to assign $l$ values and extract spectroscopic factors. Two new very low-lying levels were identified - a $p_{\frac{1}{2}}$ at ∼0.005 MeV in ${}_{}{}^{203}{}_{}{}^{}\mathrm{Hg}$ and a $f_{\frac{5}{2}}$ at ∼0.028 MeV in ${}_{}{}^{201}{}_{}{}^{}\mathrm{Hg}$. The ($d,t$) reaction only excited shell-model neutron-hole levels, while the ($d,p$) reaction excited shell-model neutron-particle levels above the $N=126\mathrm{}$ gap with greatest intensity in the heavier mercury isotopes. In the lighter mercury isotopes, the ($d,p$) reaction increasingly excited the neutron-hole states until in ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ the neutron-hole states are excited with greatest intensity. Fragmentation of all the single-particle and single-hole levels is seen and tends to increase in the lighter mercury isotopes.

The photoproton spectra and the photoproton yield curves have been measured for ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{117}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{122}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{124}{}_{}{}^{}\mathrm{Sn}$ using the electrodisintegration reaction. Several proton peaks through isobaric analog states are found in each proton spectrum. In ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$ it was found that 8.3- and 8.0-MeV proton groups were emitted from an analog state at 19.2 MeV. For the other isotopes the excitation energies of the analog states were also estimated by assuming the same decay mode as that of ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$. The yield curves of protons with an energy from 5.1 to 10.2 MeV have two breaks at each isotope corresponding to isobaric analog states. The excitation energies and the integrated cross sections were also determined.

The precompound theory of particle emissions predicts for the most energetic particles an especially simple dependence of the emission probability upon residual excitation energy. This paper examines this dependence, and compares it with experiment, to obtain the following results: (a) a distinction between processes involving even and odd nuclei; (b) values of single-particle densities, $g$, of plausible magnitude, whose uncertainties (due to experimental error in the data) are, however, too large to allow a firm conclusion about their energy dependence; and (c) the expectation that a reduction in experimental error by a factor of 2 or 3 might allow a test of a more detailed description of the residual nucleus's structure.

An experimental investigation of the influence of high hydrostatic pressure on the decay constant of ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ has been performed. By the use of a multianvil high-pressure apparatus, a carrier-free source of ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ was compressed at a pressure of 100 kbar. The observed decay rate of the compressed ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ source was compared with that of a standard ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ source in the normal uncompressed state. The fractional increase in the decay constant, $\frac{\Delta \lambda }{\lambda }$, of the compressed ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ under that pressure was found to be (4.6 ± 2.3) × ${10}^{-4\mathrm{}}$. Our result agrees with that observed by Bainbridge, $\frac{\Delta \lambda }{\lambda }=(2.3\mathrm{}\pm 0.5)\times {10}^{-4\mathrm{}}$, to within a factor of about 2. Comparison with theoretical studies by other workers is also discussed.

The distribution of mass in the spontaneous fission of ${}_{}{}^{256}{}_{}{}^{}\mathrm{Fm}$ has been investigated by the radiochemical determination of the fission yields for 28 mass chains. The mass distribution is asymmetric with a peak-to-valley ratio of ∼12. The average masses of the light and heavy groups are 111.9 and 141.0, respectively. The fission-yield data indicate a value of 3 ± 1 for $\overline{\nu }$, the average number of neutrons emitted per fission. A comparison of the characteristics of the mass distribution for low-energy fission of nuclides ranging from ${}_{}{}^{227}{}_{}{}^{}\mathrm{Th}$ to ${}_{}{}^{256}{}_{}{}^{}\mathrm{Fm}$ is given.

A systematic study of 14 unbound analog states in Tc isotopes was performed via the ${}_{}{}^{92, 94, 96}{}_{}{}^{}\mathrm{Mo}({}_{}{}^3{}_{}{}^{}\mathrm{He},d)$ reactions. Proton form factors were calculated using a simple single-particle resonance model. The proton spectroscopic factors deduced with the distorted-wave Born approximation agree well with the known neutron spectroscopic factors for the parent states obtained from ($d,p$) reactions. We conclude that this simple model is adequate for the calculation of spectroscopic factors to unbound analog states in these isotopes.

Nuclear matrix elements in the ${\frac{5}{2}}^{-}(210\mathrm{}-\mathrm{keV} \beta ){\frac{3}{2}}^{+}(279\mathrm{}-\mathrm{keV} \gamma ){\frac{1}{2}}^{+}$ $\beta -\gamma$ cascade in ${}_{}{}^{203}{}_{}{}^{}\mathrm{Hg}$ have been extracted, and comparison has been made with conserved-vector-current (CVC) theory predictions for the vector-matrix-element ratio $\int \frac{\overrightarrow{\alpha }}{\left(\int i\frac{\overrightarrow{\mathrm{r}}}{R}\right)}$. This ratio was found to be significantly smaller than the CVC prediction based on the assumption that the Coulomb Hamiltonian is diagonal. Reasonably good limits have been placed on the matrix elements in spite of the fact that the Coulomb-enhanced matrix element combination tends to dominate the transition. The nuclear matrix elements do not support a strict single-particle picture of this $\beta$ decay, in agreement with the current knowledge of the structure of the initial and final states.

$\gamma$ singles spectra of mass-separated ${}_{}{}^{239}{}_{}{}^{}\mathrm{Am}$ (11.9 ± 0.1 h) samples have been measured with high-resolution Ge(Li) detectors. Conversion-electron spectra were measured at 0.1% resolution with a magnetic spectrometer and also with a cooled Si(Li) detector. An $M1\mathrm{}$ multipolarity was found for the weak 124.42-keV transition from the previously known 511.84-keV state to the $\frac{9}{2}+$ level at 387.42 keV. The 511.84-keV state in ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ is therefore designated as the spin-$\frac{7}{2}$ member of the $\frac{7}{2}+\left(624\right)\mathrm{}$ Nilsson state. New very weak intraband transitions (101.96 keV, $E2\mathrm{}$ and 57.3 keV, predominantly $M1\mathrm{}$) depopulating the $\frac{9}{2}+$ state at 387.42 keV support its spin assignment. Atomic electron binding energies for the $K$, $N_{1-4}$, $O_2$, and $O_3$ shells in Pu were obtained; small revisions in best values for Pu electron binding energies are suggested. $\mathrm{Log}\mathrm{ft}$ values for the electron-capture transitions ${}_{}{}^{239}{}_{}{}^{}\mathrm{Am}$ → ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ were derived.

The decay of ${}_{}{}^{198}{}_{}{}^{}\mathrm{Bi}$ and ${}_{}{}^{200}{}_{}{}^{}\mathrm{Bi}$ to levels in the corresponding Pb daughters have been investigated using sources which were both mass-separated and chemically processed. $\gamma$-ray and conversion-electron singles spectra were obtained, as well as $\gamma -\gamma$ prompt- and delayed-co-incidence spectra. These data yield levels in ${}_{}{}^{198}{}_{}{}^{}\mathrm{Pb}$ at the following energies (spin-parities): 1062.9 ($2^{+}$), 1624.9 ($4^{+}$), 1822.3 [${\mathrm{}\left(5\right)\mathrm{}}^{-}$], and 2139.8 [${\mathrm{}\left(7\right)\mathrm{}}^{-}$] keV. Those in ${}_{}{}^{200}{}_{}{}^{}\mathrm{Pb}$ are at 1026.3 ($2^{+}$), 1488.3 ($4^{+}$), 1907.9 [${\mathrm{}\left(5\right)\mathrm{}}^{-}$], and 2152.9 [${\mathrm{}\left(7\right)\mathrm{}}^{-}$) keV. The half-life of the 1822-keV level in ${}_{}{}^{198}{}_{}{}^{}\mathrm{Pb}$ was determined to be 63.3 ± 2.5 nsec, and those of the 1908- and 2153-keV levels in ${}_{}{}^{200}{}_{}{}^{}\mathrm{Pb}$ are 1.50 ± 0.08 and 47.6± 2.5 nsec, respectively.

Solid-state detectors have been used to perform on-line measurements of $\gamma$-ray and conversion-electron intensities in ${}_{}{}^{133,135,136}{}_{}{}^{}\mathrm{Xe}$, ${}_{}{}^{135,137,139}{}_{}{}^{}\mathrm{Cs}$, and ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$. Conversion coefficients were determined for 37 transitions. $\mathrm{Log}\mathrm{ft}$ values were calculated on the basis of reported level schemes. The deduced multipolarities and $log\mathrm{ft}$ values were combined with published reaction and angular-correlation results to assign spins and parities to 24 excited levels of the mentioned nuclei. The obtained $J\pi$ contributed 13 new experimentally-well-defined $\beta$-transition probabilities to the systematics of this magnitude. In ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$ and ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$, three levels with known half-lives were determined to be depopulated by pure-$E2\mathrm{}$ transitions; the retardation factors as compared to the Weisskopf estimate were calculated. Apart from $J\pi$ assignments, some additional minor contributions were made to the knowledge of the level structure in ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$ and ${}_{}{}^{139}{}_{}{}^{}\mathrm{Cs}$. The number of possible spins and parities for some of the excited levels in the nuclei studied was reduced by analyzing the systematic trends of measured $J\pi$ values in their neighborhood. No modelistic considerations were taken into account for this purpose.

The isospin-dependent particle-hole interaction of Bansal and French is shown to predict adequately the energies of the anomalously low-lying $J\pi =\frac{1}{2}$- states in ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$.

A simple procedure of estimating individual resonance energies is discussed, in which both shape and compound resonances are treated by the single closed-channel Hamiltonian ${\mathcal{H}}_{\mathrm{QQ}}$. The equivalence of the method and the strength eigenvalue problem is proved and the role of the shift operator in the generalized variational-bounds formulation is further clarified.