The delayed neutrons from neutron-induced fission in ${}_{}{}^{232}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$, ${}_{}{}^{238}{}_{}{}^{}\mathrm{Pu}$, ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$, ${}_{}{}^{242}{}_{}{}^{}\mathrm{Am}_{}^m{}_{}{}^{}$, ${}_{}{}^{245}{}_{}{}^{}\mathrm{Cm}$, and ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ were studied for the first time; those from ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$, ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$, and ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$ were measured again. The data were used to develop an expression for the prediction of the absolute delayed neutron yield, and the prediction of delayed neutron emission with time. This approach accurately predicts observed delayed neutron yields and decay characteristics. A fission product yield model was used in conjunction with delayed neutron emission probability to analytically predict delayed neutron characteristics. The results of this analysis are in excellent agreement with experimental values.

RADIOACTIVITY Delayed neutron yield from thorium and transuranium elements, measured and calculated values.

High precision data have been obtained for the polarization analyzing power $A\left(\theta \right)$ in $\mathrm{pp}$ elastic scattering from 12 to 43° c.m. at 796 MeV. These data extend the angular range of data previously published by this group. Data at 428 MeV have also been obtained and are in agreement with recent double scattering data.

NUCLEAR REACTIONS ${}_{}{}^1{}_{}{}^{}\mathrm{H}\mathrm{}(p,p)\mathrm{}{}_{}{}^1{}_{}{}^{}\mathrm{H}$, $E=428, 796$ MeV; measured $A\left(\theta \right)$; $\theta =12\mathrm{} \mathrm{to} 43°$ c.m.

We present measured angular distributions for ${\pi }^{+}$-elastic scattering at 30 and 50 MeV from selected targets with $A=12\mathrm{} \mathrm{to} 208$. These angular distributions were analyzed using a phenomenological optical potential of first-order form. The mass dependence of the potential strength parameters displays the isospin dependence expected from the free $\pi N$ interaction.

NUCLEAR REACTIONS Elastic scattering of 30 and 50 MeV ${\pi }^{+}$ from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Angular distributions: $25°<{\theta }_{\mathrm{LAB}}<160\mathrm{}°$. Optical model analysis of cross-section data.

Recent (${\pi }^{+},p$) angular distribution measurements for ground state transitions in several light nuclei exhibit energy independence in both shape and magnitude over a wide energy range. They also exhibit a simple exponential decrease with momentum transfer, $\exp (-\frac{q}{\lambda })$. The parameter $\lambda$ has a smooth variation with target mass $A$. The magnitudes of the cross sections are proportional to the spectroscopic strength of the transition except for ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}({\pi }^{+},p)$, which is a factor of 3 high and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}({\pi }^{+},p)$, which is a factor of 10 low. A single neutron pickup distorted-wave calculation appears to be incapable of reproducing the experimental data and will require a major modification. A two nucleon model is briefly examined and shows potential for success.

NUCLEAR REACTIONS ($\pi ,p$) on ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{12,13,14}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$; $5<\mathrm{}{T}_{\pi }<200\mathrm{}$ MeV compilation of data, theoretical study of mechanism.

We suggest that the observed 6% Goldberger-Treiman discrepancy is due in part to a 3% variation in the pionnucleon form factor and in part due to a 3% variation in the pion decay form factor from $q^2=m_{\pi }^{}{}_{}{}^2$ to $q^2=0\mathrm{}$.

NUCLEAR REACTIONS Goldberger-Treiman discrepancy, $\pi \mathrm{NN}$ form factor, pion decay form factor, chiral symmetry breaking, current quark masses.

The static pion $p$-wave self-energy in symmetric nuclear matter is calculated, taking into account the effects of nucleon particle-hole (ph) and $\Delta$-isobar nucleon-hole ($\Delta \mathrm{h}$) states. The residual interaction between ph states is derived from a Brueckner $G$ matrix which depends on the starting energy and three momentum variables. The coupling of ph and $\Delta \mathrm{h}$ states and the $\Delta \mathrm{h}-\Delta \mathrm{h}$ interaction is described by $\pi$ and $\rho$ exchange taking into account the effects of $\mathrm{NN}$ correlations. The resulting self-energies are analyzed in the model of constant interaction strengths which is commonly used. This analysis yields effective interaction strengths weakly depending on the momentum of the pion field as well as on the nuclear density. Only in the limit of vanishing pion momentum the strength of the ph interaction is connected with the Landau parameter $G_0^{\prime }$. The present calculation yields pion condensation at twice the empirical nuclear matter density when isobars are included.

NUCLEAR STRUCTURE Particle-hole interaction, nuclear matter. Brueckner $G$ matrix, isobar configurations, pion condensation.

The deuteron disintegration processes $\nu \left(\overline{\nu }\right)+d\to \nu \left(\overline{\nu }\right)+n+p$ have been studied at intermediate energies in impulse approximation using closure over the final dinucleon states. The disintegration cross section $\sigma$ has been discussed as a function of neutrino (antineutrino) energy in various SU(2)×U(1) models for the helicity conserving weak neutral currents. A discussion on the helicity flipping weak neutral currents models of $S$, $P$, $T$ couplings is also given.

NUCLEAR REACTIONS $d(\nu ,\nu )np$: closure approximation, deuteron disintegration, neutral currents, helicity conserving theories, helicity flipping theories.

The question of whether the ten generators for the Poincaré group as given in a field theoretical model can be reduced to the pure particle space without invalidating the commutation relations is studied. We come to a positive answer in the framework of perturbation theory. In a simple model of scalar particles exchanging scalar bosons we construct the generators in lowest order in the coupling constant and compare the expressions with the ones found by Foldy and Krajcik in a $\frac{1}{c^2}$ expansion. We recover their result, but find in addition new terms in the interaction, which remained principally undetermined in their treatment. Possible useful features of the "relativistically generalized Schrödinger equation" are pointed out.

NUCLEAR STRUCTURE Relativistic corrections.

For the inclusive cross section $B+A\to C+X$, with the beam momentum per nucleon equal to $p$, and with the conditions $1\lesssim B\lesssim p{m}^{-1\mathrm{}}\ll A$, $\mathrm{Bp}{\mathrm{}\left(\mathrm{Am}\right)\mathrm{}}^{-1\mathrm{}}<1\mathrm{}$, we reproduce the scaling law for the light-nucleus ($B$) fragmentation, derived by Schmidt and Blankenbecler, and find the violation of the scaling law for the heavy-nucleus ($A$) fragmentation. To account for the heavy-nucleus fragmentation we use the cluster model of Landau and Gyulassy. We work in the light-front scheme, in which all particles, including the intermediate one, are on their mass shell, while the off-shell continuation is made only in the "minus" component of the total momentum. That gives us some control of the off-shell behavior of the inclusive subprocess $a+b\to C+d$, in terms of which one determines the process $B+A\to C+X$.

NUCLEAR REACTIONS $A(B,\pi )X$, $1\lesssim B\lesssim p{m}^{-1\mathrm{}}\ll A$, $\mathrm{Bp}{\mathrm{}\left(\mathrm{Am}\right)\mathrm{}}^{-1\mathrm{}}<1\mathrm{}$. Asymmetry in the scaling laws for the light ($B$) and heavy ($A$) nucleus fragmentation. Hard scattering model and cluster fragmentation in the light front scheme.

Direct emission models which have been proposed for hadronically induced inclusive reactions are tested by comparison with electromagnetically induced reactions. It is found that proton emission in both ($p,p^{\prime }$) and ($\gamma ,p$) reactions is consistently described by a direct emission model. The available ($e,\alpha$) data are sufficiently sensitive to the assumed residual excitation energy of the model that a firm conclusion cannot be drawn for the role of direct emission in fragmentation processes. Predictions for particle multiplicities corresponding to two direct emission models are discussed.

NUCLEAR REACTIONS Test of models for ($p,p^{\prime }$), ($\gamma ,p$), ($p,\alpha$), and ($e,\alpha$) reactions at intermediate energies; predictions of charged particle multiplicities in ($p,p^{\prime }$) reaction.

The $\gamma$-ray spectrum of 14.1-h ${}_{}{}^{240}{}_{}{}^{}\mathrm{U}$ was obtained almost free of interference by the much more intense $\gamma$ radiation from its ${}_{}{}^{240}{}_{}{}^{}\mathrm{Np}_{}^m{}_{}{}^{}$ daughter by means of continuous radiochemical separations. Thus 16 new transitions (49.1-299.8 keV) were revealed in addition to the single one at 44.1 keV previously identified, and a tentative decay scheme for ${}_{}{}^{240}{}_{}{}^{}\mathrm{U}$ is proposed. A detailed study of separated ${}_{}{}^{240}{}_{}{}^{}\mathrm{Np}_{}^m{}_{}{}^{}$ showed $70\gamma$ transitions whose $E_{\gamma }$ and $I_{\gamma }$ values agree well with previous data, and in addition 29 new transitions were found. The absolute intensity of the 554.6-keV $\gamma$-ray transition is (20.6±0.5)%, the ${}_{}{}^{240}{}_{}{}^{}\mathrm{Np}_{}^m{}_{}{}^{}$ half-life is 7.22±0.02 min, and the fraction decaying by isomeric transition is (0.12±0.01)%. A decay scheme of ${}_{}{}^{240}{}_{}{}^{}\mathrm{Np}_{}^m{}_{}{}^{}$ is proposed which shows several new levels in ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$ and some changes in previous $I^{\pi }$ and $K^{\pi }$ assignments. The isomeric state is assigned $I^{\pi }=1^{\mathrm{}(+)\mathrm{}}$, $K^{\pi }=0^{\mathrm{}(+)\mathrm{}}$ with the probable configuration ${\frac{7}{2}}^{+}{\mathrm{}\left[633\right]\mathrm{}}_p$, ${\frac{7}{2}}^{+}{\mathrm{}\left[624\right]\mathrm{}}_n$.

RADIOACTIVITY ${}_{}{}^{240}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{240}{}_{}{}^{}\mathrm{Np}_{}^m{}_{}{}^{}$ from ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}\stackrel{\alpha }{\to }{}_{}{}^{240}{}_{}{}^{}\mathrm{U}\stackrel{{\beta }^{-}}{\to }{}_{}{}^{240}{}_{}{}^{}\mathrm{Np}_{}^m{}_{}{}^{}$; radiochemistry, Ge(Li) and $4\pi$ gas proportional detectors. Measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$; deduced $I_{\beta }$, $log\mathrm{ft}$, decay schemes, $I$, $\pi$, Nilsson assignments.

Gamma-ray spectroscopic experiments have been performed on the $\frac{{\beta }^{+}}{\epsilon }$ decay of 2.50-h ${}_{}{}^{116}{}_{}{}^{}\mathrm{Te}$. Results from these experiments and from complementary in-beam $\gamma$-ray angular distributions were used to construct a decay scheme. Twenty-one $\gamma$ rays were identified and placed in the decay scheme containing states in ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sb}$ at $0(J^{\pi }=3^{+})$, 93.7 ($1^{+}$), 103.0 ($2^{+}$), 446.0 (3), 550.9 (2), 574.4 (2), 731.7 ($1^{+}$), 917.7 ($1^{+}$), and 1158.3 ($1^{+}$) keV. The structures of the odd-odd Sb states are analyzed and discussed in simple shell-model terms.

RADIOACTIVITY ${}_{}{}^{116}{}_{}{}^{}\mathrm{Te}$ [from ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}({}_{}{}^3{}_{}{}^{}\mathrm{He},3n){}_{}{}^{116}{}_{}{}^{}\mathrm{Te}$]; measured $E_{\gamma }$, $I_{\gamma }$, deduced ${\alpha }_K$, ${\alpha }_{\mathrm{tot}}$; deduced $log\mathrm{ft}$; ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sb}$ deduced levels, $J$, $\pi$; Ge(Li) singles and $\gamma -\gamma$ coinc.; shell-model considerations.

${}_{}{}^{21}{}_{}{}^{}\mathrm{F}\left({\beta }^{-}\right){}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ is re-examined. $\beta$ branches are observed as follows [${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}{E}_x$ (keV),% $\beta$ branch]: 0, 9.6(3.0); 351, 74.1(3.0); 1746, 16.1(1.0); 3736, 3.1(4)×${10}^{-3\mathrm{}}$; 3884, 4.0(4)×${10}^{-3\mathrm{}}$; 4525, 43(3)×${10}^{-3\mathrm{}}$; 4685, 77(5)×${10}^{-3\mathrm{}}$. The half-life was measured to be 4.158(20) s. Precision $\gamma$-ray measurements were made for the ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ 351→0 and 1746→351 transitions and the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ 1634→0 transition. Results for the $\gamma$ energies are 350.725(8), 1395.131(17), and 1633.602(15) keV. $log\mathrm{ft}$ values are calculated. Comparisons of the present results are made to the shell-model calculations of Lanford and Wildenthal and to the analog ${\beta }^{+}$ decay of ${}_{}{}^{21}{}_{}{}^{}\mathrm{Mg}$ to ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$. It is concluded that uncalculated Coulomb effects are a major block to the sensitivity of such comparisons.

RADIOACTIVITY ${}_{}{}^{21}{}_{}{}^{}\mathrm{F}$ [from ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}\mathrm{}(t,p)\mathrm{}$]; measured $I_{\gamma }$, $E_{\gamma }$, $T_{\frac{1}{2}}$; deduced $\beta$ and $\gamma$ branching, $log\mathrm{ft}$ values; compared with analog decay and theory.

The ${\beta }^{+}$ decay of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ has been studied with a Ge(Li)-NaI(Tl) escape-suppression spectrometer. The number of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ $\gamma$ transitions observed following ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ decay has been increased from 19 to 44. Definite new ${\beta }^{+}$ branches were observed to ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ levels at 105 76, 108 21, and 113 14 keV. An enhanced $E2\mathrm{}$ transition from the $4^{+}$ 9301-keV level to the $2^{+}$ 7349-keV level was sought for and found. A probable 8439→7349 $4^{+}$→$2^{+}$ transition was also observed. The contribution of these new experimental results to an elucidation of the band structure of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ is discussed.

RADIOACTIVITY ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ [from ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}\mathrm{}(p,n)\mathrm{}$]; measured $E_{\gamma }$, $I_{\gamma }$, ${\beta }^{+}$ and $\gamma$ branchings; deduced $B\left(E2\mathrm{}\right)\mathrm{}$, $log\mathrm{ft}$.

A line of first order phase transitions terminating in a second-order phase transition separates the parameter space of the interacting boson model into a vibrator region [U(59) limit] and a rotor region [SU(3) and O(6) limits]. This first order phase transition line is surrounded by two spinodal lines demarking the limits of metastable nuclear isomers. No other islands of metastability exist in this parameter space.

NUCLEAR STRUCTURE Phase transitions, interacting boson model, critical properties, geometric properties.

Eigenvectors have been calculated for the $A=18,19,20,21,\mathrm{and}26$ nuclei in an $\mathrm{sd}$ shell basis. The decomposition of these states into their shell model components shows, in agreement with other recent work, that this distribution is not a single Gaussian. We find that the largest amplitudes are distributed approximately in a Gaussian fashion. Thus, many experimental measurements should be consistent with the Porter-Thomas predictions. We argue that the non-Gaussian form of the complete distribution can be simply related to the structure of the Hamiltonian.

NUCLEAR STRUCTURE ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$, ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$, ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$; calculated low-lying states with shell model. Examined amplitude distributions.

The parity mixing in the 1040, 1080 keV doublet ($J,T=0^{+},1\mathrm{} \mathrm{and} 0^{-},0, \mathrm{respectively}$) of ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ has been calculated in the frame of the spherical shell model with different residual interactions. In this case only the isovector part of the parity violating potential is effective, and only the dominating one-pion-exchange term has been considered. The shell model space includes the $0p_{\frac{1}{2}}$, $0d_{\frac{5}{2}}$, and $1s_{\frac{1}{2}}$ orbits. The influence of a further truncation of the model space has also been investigated. The results appear not to depend drastically on the choice of the residual interaction among those reported in the literature. The same conclusion appears to hold for the matrix element of the one-pion-exchange potential between the ${1/2}^{-}$ and ${1/2}^{+}$ levels at 2788 and 2796 keV in ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$.

NUCLEAR STRUCTURE Parity mixing calculation for the $0^{+}$1, $0^{-}$0 doublet in ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$.

The interpretation of reactor-antineutrino-induced experiments in the investigation of neutrino oscillations is, in a decisive way, dependent on reliable calculations of the initial antineutrino spectra. Present calculations ignore the effects of low-lying structures in the beta strength function. These will have, however, a drastic influence on the $\beta$-decay properties of the fission products and thus on the shape of the antineutrino spectra.

NUCLEAR STRUCTURE Influence of structures in the beta strength function on reactor antineutrino spectra. Consequences for neutrino oscillation experiments.

Values of the total reaction cross section ${\sigma }_R$ for the system ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ are obtained from the optical model analysis of elastic scattering data at c.m. energies equal to 60, 93, and 135 MeV. An averaging method based on the strong correlation found between ${\sigma }_R$ and the imaginary diffuseness is presented and utilized to obtain ${\sigma }_R$ and an estimate of its uncertainty. The derived values are consistent with calculations showing increased nuclear transparency.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $E=140, 218, 315$ MeV; measured $\sigma (E;\theta )$ for g.s.; optical model analysis. Deduced total reaction cross section.

${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$ decay has been measured and a new ${}_{}{}^{146}{}_{}{}^{}\mathrm{Eu}$ level scheme established with excited levels at 114, 230, 384, 421, 498, and 690 keV having spins and parities of $3^{-}$, $2^{-}$, $1^{-}$, ${\mathrm{}\left(2\right)\mathrm{}}^{-}$, and $2^{-}$, respectively. From experimental relative $P_k$ values in ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$ electron capture decay and from $\frac{{\beta }^{+}}{\mathrm{EC}}$ ratios measured in ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Dy}$ decay, lower and upper limits for the ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Dy}$ decay energies have been determined to be $950<\mathrm{}{Q}_{\mathrm{EC}}\left({}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}\right)<\mathrm{}1054\mathrm{}$ keV and $1710<\mathrm{}{Q}_{\mathrm{EC}}\left({}_{}{}^{150}{}_{}{}^{}\mathrm{Dy}\right)<\mathrm{}1814\mathrm{}$ keV. The upper limits on these decay energies were smaller than the extrapolated masses indicated. The ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$ decay energy is in accordance with recent reaction data.

RADIOACTIVITY ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{150}{}_{}{}^{}\mathrm{Dy}$; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma$, $X_{\gamma }$ coin; ${}_{}{}^{146}{}_{}{}^{}\mathrm{Eu}$ levels deduced. ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$, ${}_{}{}^{150}{}_{}{}^{}\mathrm{Dy}$; deduced $Q$ values.