A new radioactivity of Np was discovered by chemical separations from targets of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ and ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$ irradiated with 30-160 MeV neutrons. Five $\gamma$ rays were identified with $E_{\gamma },I_{\gamma }:159.1\mathrm{} \mathrm{keV},32;265.1\mathrm{} \mathrm{keV},24;785.7\mathrm{} \mathrm{keV},\left(100\right);944.8\mathrm{} \mathrm{keV},63; \mathrm{and} 1104 \mathrm{keV}, 0.6$. The half-life is 5.5±0.1 min and various cross bombardments established that the mass number is 242. $I^{\pi }$ was assigned $6^{+}$ with the configuration ${\frac{5}{2}}^{+}{\mathrm{}\left[642\right]\mathrm{}}_p$, ${\frac{7}{2}}^{+}{\mathrm{}\left[624\right]\mathrm{}}_n$ and a decay scheme is proposed.

RADIOACTIVITY 5.5-min ${}_{}{}^{242}{}_{}{}^{}\mathrm{Np}$ from ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}\mathrm{}(n,p2n)\mathrm{}$ and ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}\mathrm{}(n,p)\mathrm{}$; radiochemistry, Ge(Li). Measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$; deduced $E_{{\beta }^{-}}$, $log\mathrm{ft}$, partial decay scheme, $I$, $\pi$, Nilsson assignments.

A ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$ source has been used to study the photoactivation of the 336 keV ($T_{\frac{1}{2}}\sim 4.3$h) isomeric level of ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$. In contrast to earlier investigations, we have considered the possibility of nonresonant processes and have developed a technique which allows us to distinguish between activation via the resonance fluorescence of the 1078 keV ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$ level, and by nonresonant processes involving the 1172 and 1332 keV ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$ photons. We have found that nonresonant processes are the dominant modes of activation. Although various possible mechanisms for the nonresonant excitation have been considered, none seem sufficiently strong to explain our results.

RADIOACTIVITY ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$; studied photoactivation with ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$, measured ${\Gamma }_0$ for 1078 keV, investigated excitation mechanism.

The $\beta -\gamma$ angular correlation for the decay of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ has been measured using a symmetric four detector system. The ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ activity was produced by the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}\mathrm{}(p,n)\mathrm{}{}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ reaction and transported by a He jet to the detector chamber. Care was exercised to ensure that the $\beta$ source was well defined. Correlation data were acquired for ${\theta }_{\beta -\gamma }=90\mathrm{}° \mathrm{and} 180°$ as a function of positron energy. The correlation data were analyzed for both linear and quadratic energy dependence. We report as the best estimate for the linear coefficient (- 5.0 ± 0.8) × ${10}^{-3\mathrm{}}$ ${\mathrm{MeV}}^{-1\mathrm{}}$ and for the quadratic coefficient (2.9 ± 0.8) × ${10}^{-4\mathrm{}}$ ${\mathrm{MeV}}^{-2\mathrm{}}$. Incorporating the results with other measurements in the $A=20\mathrm{}$ system, we find an upper limit for the second class current contribution to the correlation which is no more than 20% of the weak magnetism contribution and is consistent with zero.

NUCLEAR REACTIONS Radioactivity ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$; measured $\beta -\gamma$ angular correlation. Determined induced weak currents.

With the technique of nuclear magnetic resonance on oriented nuclei, the magnetic hyperfine splitting of ${}_{}{}^{93}{}_{}{}^{}\mathrm{Mo}_{}^m{}_{}{}^{}\mathrm{Fe}$ has been investigated in external magnetic fields $B_0=1\mathrm{}\dots 7$ kG at temperature of ∼0.01 K. The zero-field splitting and the resonance shift with $B_0$ were measured $\left|\frac{g{\mu }_N{B}_{\mathrm{HF}}}{h}\mathrm{}\right|=183.84\left(1\mathrm{}\right)\mathrm{}$ MHz and $\left|\frac{g{\mu }_N}{h}\mathrm{}\right|=0.721\left(8\mathrm{}\right)\mathrm{}$ MHz/kG, yielding consistent values for the nuclear $g$ factor of 0.947(19) and 0.946(9), respectively. From the mean value $\mathrm{}\left|g\right|=0.946\mathrm{}\left(8\right)\mathrm{}$ the magnetic moment is derived as $\left|\mu \mathrm{}\right|=9.93\left(8\mathrm{}\right)\mathrm{}{\mu }_N$. This confirms the structure of the ${21/2}^{+}$ state as ${|{\left(\pi g_{{\frac{9}{2}}^{+}}\right)}_{{8^{+}}^2}\nu d_{{\frac{5}{2}}^{+}}〉}_{{\frac{21}{2}}^{+}}$ for which $\mu =10.00\mathrm{}\left(5\right)\mathrm{}{\mu }_N$ is expected taking into account experimentally known magnetic properties of neighboring nuclei. Our measurements show that the additivity relation for the magnetic moments holds well for this state, and that the results of a previous nuclear magnetic resonance on oriented nuclei measurement must be erroneous.

RADIOACTIVITY ${}_{}{}^{93}{}_{}{}^{}\mathrm{Mo}_{}^m{}_{}{}^{}$ [from ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}(\alpha ,3np)$]; measured $I_{\gamma }$ ($\theta ,T,\nu$) of oriented states; NMR on oriented nuclei. Deduced $g$, $\mu$, relaxation times.

We construct a relativistic model of interacting nucleons and mesons. The character of the model is phenomenological in that we make extensive use of the relativistic quasipotentials obtained in the study of the one-boson-exchange model of nuclear forces. We show that in the static limit for the meson field we can derive a relativistic version of the Bethe-Brueckner theory of nuclear matter. (The corrections due to the nonstatic aspects of the field are expected to be small.) The method may be extended to provide a basis for a relativistic Brueckner-Hartree-Fock theory of finite nuclei.

NUCLEAR STRUCTURE Relativistic many-body theory; derivation of relativistic Bethe-Brueckner theory of nuclear matter.

We extend the theory of nuclear matter to include a relativistic description of nucleon motion. In particular we allow for negative energy components in the nucleon wave function. The amplitude for these components is calculated using an extended version of the one-boson-exchange model of nuclear forces. We find that the inclusion of negative energy states (pair currents) provides a strongly density dependent repulsive interaction. (If one limits oneself to a description involving positive energy states only, this interaction appears as an effective repulsive many-body force.) Our extended theory leads to major modification of the saturation properties of nuclear matter. For example, a boson-exchange force which, in a standard calculation, leads to significant overbinding of nuclear matter at much too high a saturation density yields, in our relativistic analysis, quite good agreement with the generally accepted empirical values for the binding energy and density of nuclear matter. (This potential has strong tensor coupling for the $\rho$ meson and a weak tensor force. These features are favored at this time on the basis of other theoretical considerations.) We conclude that, contrary to current thought, nuclear matter should be treated as a relativistic system.

NUCLEAR STRUCTURE Relativistic effects in the saturation properties of nuclear matter.

Starting from a simplified description, treating proton two-particle two-hole (2p-2h) excitations coupled with spherical quadrupole vibrations in interaction with the low-lying quadrupole vibrational states in doubly-even ${}_{}{}^{112-118}{}_{}{}^{}\mathrm{Sn}$ nuclei, we are able to account for the regular $\Delta J=2\mathrm{}$ band structure on top of excited $J^{\pi }=0^{+}$ states. Energy spectra as well as $E2\mathrm{}$ and $E0\mathrm{}$ decay properties are calculated and are extensively compared with recent experimental data.

NUCLEAR STRUCTURE Proton 2p-2h-core coupling calculations, collective bands in ${}_{}{}^{112-118}{}_{}{}^{}\mathrm{Sn}$; energy spectra, $E2\mathrm{}$ and $E0\mathrm{}$ transitions.

A comparison between the finite Dyson-type and the infinite Holstein-Primakoff-type boson expansion is presented, considering both particle-hole and pairing type excitations. The significance of truncating to the truly collective branches is emphasized, and the convergence of the Holstein-Primakoff expansion is discussed. It is shown that in both expansions there is no need to construct physical basis states. Complete equivalence between the two types of expansion is exhibited by treating these excitations within models which are schematic but not totally unrealistic.

NUCLEAR STRUCTURE Boson expansion theory, convergence, comparison of different methods, finite Dyson expansion, infinite Holstein-Primakoff expansion, pairing and particle-hole collective motions.

Particle-core coupling calculations on heavy odd-odd and odd-even Sb nuclei have been carried out, starting from a shell-model description. Starting from a description of the core system (Sn nuclei) and a multipole-multipole protonneutron interaction, we have derived particle-core coupling matrix elements (applicable to odd-mass as well as to odd-odd nuclei). Detailed calculations have been carried out for ${}_{}{}^{132,130,129}{}_{}{}^{}\mathrm{Sb}$. In the latter case, extensive comparison is made with macroscopic particle-core coupling calculations.

NUCLEAR STRUCTURE Particle-core coupling, shell-model approach. Application to ${}_{}{}^{132,130,129}{}_{}{}^{}\mathrm{Sb}$.

Using separable potentials for the most important deuteron partial waves, we constructed deuteron wave functions with the Gross equation. For that we parametrized the $S$ and the $D$ waves in such a way that they approximately agree with the wave functions computed with the Paris or Nijmegen potentials. The additional off-the-mass-shell state was taken as a simple Yamaguchi $P$-wave form factor. The so obtained potentials were fitted to the experimental phase shifts and the quadrupole moment, where we also used relativistic formulas. We found a fairly good agreement with the results of Gross for meson theoretical potentials.

NUCLEAR STRUCTURE ${}_{}{}^2{}_{}{}^{}\mathrm{H}$: wave functions, separable potentials; one nucleon off mass shell, relativistic corrections to quadrupole moment.

A collective formalism first proposed by Deal to describe isoscalar dipole excitations in electron scattering is extended to include excitations of these modes by hadron scattering. Distorted-wave Born approximation calculations are performed using this collective isoscalar $L=1\mathrm{}$ form factor to describe the excitation of the $1^{-}$, $T=0\mathrm{}$ state at $E_x=7.12\mathrm{}$ MeV ($1\hslash \omega$ character) in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and a newly proposed candidate for the isoscalar giant dipole resonance ($3\hslash \omega$ character) at $E_x=21.3\mathrm{}$ MeV in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ excited in inelastic $\alpha$ scattering. A good description of the cross sections of the $1^{-}$, 7.12 MeV state in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and the $E_x=21.3\mathrm{}$ MeV bump in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ is obtained in this model exhausting 4.2% and 130% of the energy-weighted sum rule, respectively.

NUCLEAR STRUCTURE Isoscalar dipole resonance; derived form factor, energy weighted sum rule. Excitation in hadron scattering.

Different collective deformation coordinates for neutrons and protons are introduced to allow for both stretching and $\gamma$ transitions consistent with experiments. The rotational actinide nuclei ${}_{}{}^{234-238}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ are successfully analyzed in this model.

NUCLEAR STRUCTURE ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{234-238}{}_{}{}^{}\mathrm{U}$ calculated $B$ ($E2\mathrm{}$) values, collective model.

It is shown that for a closed shell plus one nucleon, when the core is allowed to deform, the procedure of variation after projection leads to a significantly different result than variation before projection. In the weak deformation limit the ratio of quadrupole moments with variation before and after projection $\frac{Q_{\mathrm{VBP}}}{Q_{\mathrm{VAP}}}$ is given by Clebsch-Gordan coefficients. In the case where $k=j,Q_{\mathrm{VAP}}$ is approximately equal to the intrinsic quadrupole moment.

NUCLEAR STRUCTURE Quadrupole moment calculated by variation after projection and compared with variation before projection as well as with the intrinsic moment.

Alpha-particle and $\gamma$-ray spectral measurements were made for ${}_{}{}^{205-208}{}_{}{}^{}\mathrm{Fr}$. A new $\alpha$ emitter ($T_{\frac{1}{2}}=0.7\mathrm{}\pm 0.1$ sec and $E_{\alpha }=6.930\mathrm{}\pm 0.005$ MeV) was observed and identified with the decay of a previously unknown isomer in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Fr}$. From the $\alpha$ particle and $\gamma$ ray intensities, $\alpha$ decay branching ratios were deduced for ${}_{}{}^{205-208}{}_{}{}^{}\mathrm{Fr}$ utilizing available information concerning the nuclides' (electron capture + positron) decay properties. Reduced widths were calculated and compared with those of neighboring nuclei.

RADIOACTIVITY ${}_{}{}^{205,206,207,208}{}_{}{}^{}\mathrm{Fr}$, measured $E_{\gamma }$, $I_{\gamma }$, $E_{\alpha }$, $I_{\alpha }$; deduced $\alpha$-branching ratios; identified ${}_{}{}^{206}{}_{}{}^{}\mathrm{Fr}_{}^m{}_{}{}^{}$. Mass separation.

The level structure of ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$ has been intensively studied by the reaction ${}_{}{}^{198}{}_{}{}^{}\mathrm{Pt}(\alpha ,2n\gamma )$, and many new levels have been identified. The results clarify some important aspects of the ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$ high-spin level structure.

NUCLEAR REACTIONS ${}_{}{}^{198}{}_{}{}^{}\mathrm{Pt}(\alpha ,2n)$, $E=26\mathrm{}-28$ MeV; measured $E_{\gamma }$, $I_{\gamma }\left(\theta \right)$, $\gamma -\gamma$ coin; ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$ deduced high-spin levels, $J$, $\pi$.

A comparison of nucleon-removal differential scattering cross sections at 35° for 190-MeV ${\pi }^{\pm }$ on ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ shows $p2n$ removal and single-nucleon removal as the most dominant. Single-nucleon removal is consistent and in good agreement with the one-step-quasifree $\pi N$ scattering model, but only if the pion interacts principally with a $p2n$ system. The outgoing nucleon charge exchange probability is measured to be ∼1/3 for ∼16-MeV nucleons. The $\pi 2n$ angular distribution and the proton energy spectrum at 35° also support the one-step-quasifree scattering with the outermost nucleons model.

NUCLEAR REACTIONS ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({\pi }^{\pm },{\pi }^{\pm }p){}_{}{}^{27}{}_{}{}^{}\mathrm{Al}_{}^{*}{}_{}{}^{}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({\pi }^{\pm },{\pi }^{\pm }p){}_{}{}^{27}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({\pi }^{\pm },{\pi }^{\pm }n){}_{}{}^{26}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({\pi }^{\pm },{\pi }^{\pm }pn){}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({\pi }^{\pm },{\pi }^{\pm }p2n){}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({\pi }^{\pm },{\pi }^{\pm }2p2n){}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({\pi }^{\pm },{\pi }^{\pm }3p3n){}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$. Measured $\sigma \left(35\mathrm{}°\right)$ using scattered ${\pi }^{\pm }$ in coincidence with $\gamma$ rays. Compare single-nucleon removal with quasifree scattering.

The ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(p,p\alpha ){}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ reaction has been measured at $E_p=101.3\mathrm{}$ MeV for coplanar quasifree angle pairs (${\theta }_{\rho }=70\mathrm{}°,{\theta }_{\alpha }=-45.7\mathrm{}°$) and out-of-plane angles $\beta =0\mathrm{}°,5°,10°,15°, \mathrm{and} 20°$. Distorted-wave impulse approximation calculations reproduce the shape of the energy sharing distributions and provide spectroscopic factors in agreement with previous work on knockout and transfer reactions.

NUCLEAR REACTIONS ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(p,p\alpha ){}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$, $E_{\mathrm{lab}}=101.3\mathrm{}$ MeV: measured $\frac{d^3\sigma }{d{\Omega }_{p}d{\Omega }_{\alpha }d{E}_p}$ for ${\theta }_p=70\mathrm{}°$, ${\theta }_{\alpha }=-45.7\mathrm{}°$, ${\beta }_{\alpha }=0\mathrm{}°,5°,10°,15°,20°$; DWIA analysis.

$p-{}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ elastic and $p-{}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ bremsstrahlung cross sections are calculated using various resonance parameters. We have found that among all the resonance parameters studied by us the Maryland parameters for $p-{}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ is the only set which fits the elastic scattering data. We have also found that those resonance parameters which give good agreement with the bremsstrahlung data at 1795 keV tend to give poor agreement with the elastic data near the 1.7-MeV resonances. Our bremsstrahlung calculations are based on the Feshbach-Yennie approximation.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}\mathrm{}(p,p)\mathrm{}{}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(p,p\gamma ){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $E_p=1.765\mathrm{}-1.895$ MeV; calculate $\frac{d\sigma }{d{\Omega }_p}$ and $\frac{d^3\sigma }{d{\Omega }_{p}d{\Omega }_{\gamma }\mathrm{dk}}$; deduced resonance parameters.

The contribution of the heavy particle stripping mechanism to the elastic scattering of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ on ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is calculated using a modified distorted-wave Born approximation approach. The resulting amplitude is combined with a conventional optical potential amplitude and the calculated cross sections are compared with measurements at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=60\mathrm{} \mathrm{and} 113$ MeV. It is found that the heavy particle stripping mechanism produces most of the observed cross sections backward of ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=100\mathrm{}°$ and that it has very little effect on forward cross sections.

NUCLEAR REACTIONS ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$)${}_{}{}^4{}_{}{}^{}\mathrm{He}$, $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=60.2\mathrm{} \mathrm{and} 113.1$ MeV; calculation of heavy particle stripping contribution; Optical model and DWBA.

The isovector giant quadrupole resonance systematically observed by inelastic electron scattering is studied using a schematic model. Analytic expressions are given for the isovector quadrupole excitation strengths. These expressions are used to estimate the energy splitting of the two isospin components and their strengths.

NUCLEAR STRUCTURE Isovector giant quadrupole resonance. Isospin splitting. Schematic model.