The half-life of ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ has been measured to be $T_{\frac{1}{2}}=54.2\mathrm{}\pm 2.1$ yr, somewhat higher than previously published values of 46.4±1.7 and 48.2±0.9 yr. The present value was obtained from the specific activity and the radioisotope concentration of several Ti${\mathrm{O}}_2$ samples, each spiked with a ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ activity of about 1.2 μCi. The specific activity was measured via the 1157 keV $\gamma$ line from the decay of the ${}_{}{}^{44}{}_{}{}^{}\mathrm{Sc}$ daughter. ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$/Ti concentrations were measured with the Argonne FN tandem accelerator in conjunction with an Enge split-pole magnetic spectrograph using the technique of accelerator mass spectrometry. An overall sensitivity of ${10}^{-10\mathrm{}}$ was achieved which proves accelerator mass spectroscopy to be a powerful tool for radioisotope detection also in a region of rather heavy ion masses. A detailed description of the subtleties of accelerator mass spectroscopy when applied to measure absolute radioisotope concentrations in this heavy mass region is presented.

RADIOACTIVITY Measured half-life of ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ via accelerator mass spectroscopy.

The strength function for deep-lying hole states in a nucleus is examined from a many-body point of view. Due to their interaction with the compound state background, such single hole excitations are interpreted as quasihole states that are not eigenstates of the nuclear Hamiltonian. These states show up as giant resonances in the strength function, with position and width determined by the real and imaginary parts of the quasihole energy. A formal theory of the strength and fragmentation of such states is developed by splitting the self-energy into background and doorway state contributions. The theory is applied to the calculation of the strength function for the isotopes of Sn using doorway states of a collective nature that consist of a hole plus collective vibrations of the target nucleus. A microscopic description of both the collective excitations and the hole state that it dresses is given in terms of a modified random phase approximation procedure that uses Green's functions for the individual single particle and single hole states that have been dressed by their interaction with the nuclear background. Specific calculations for the isotopes of Sn show good agreement with experiment.

NUCLEAR STRUCTURE Theory of single hole strength function. Green's function method for optical potential; intermediate structure doorway states. Pairing, isospin. Calculations for isotopes of Sn.

We find that a recent experimental determination of the electric polarizability of the deuteron does not yield any new information on the nucleon-nucleon interaction. Theoretical values for the central and tensor components of the polarizability are presented.

NUCLEAR STRUCTURE d; calculated electric polarizability.

The parameters of the interacting boson model are calculated in a shell model framework, using a generalized seniority basis. The effect of the neutron-proton interaction on the $s$- and $d$-boson structure is explicitly considered. The renormalization due to the truncation of the full fermion space to the $S-D$ subspace is considered by taking the effects of the $G$-pair state into account using perturbation theory. It is found that this effects mainly the single boson energies and introduces a Majorana force that favors states symmetric in neutron and proton degrees of freedom over antisymmetric ones.

NUCLEAR STRUCTURE Microscopic calculation of interacting boson approximation parameters. Shell model calculations in the generalized seniority basis.

Ground state 2p-2h correlations are explicitly calculated in a completely self-consistent way within the framework of the Tamm-Dancoff approximation using a "universal" effective nucleon-nucleon interaction of the Skyrme type. Their influence on the charge distributions of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ is studied.

NUCLEAR STRUCTURE ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40,48}{}_{}{}^{}\mathrm{Ca}$; ground state correlations; charge distributions; use of self-consistent methods.

The predictions of the interacting boson approximation are studied in the consistent $Q$ formalism in which the same parametrization of the boson quadrupole operator is used in both the Hamiltonian and in the $E2\mathrm{}$ operator. In this scheme, wave functions, relative energies of states of the same spin, and all relative $B\left(E2\mathrm{}\right)\mathrm{}$ values depend on only a single parameter, ${\chi }_Q$, which appears in the internal structure of the operator $Q$. This feature allows a number of simple results to be obtained, principally through the construction of contour plots of various observables in terms of ${\chi }_Q$ and the boson number $N$. The entire SU(3)—O(6) region, including both limiting symmetries, can be treated by allowing ${\chi }_Q$ to vary between its respective limiting values for those two symmetries. For deformed nuclei, a number of characteristic features are obtained, involving the predicted decay of the $\gamma$ band and the energy and decay of the first $0^{+}$ excitation. It is shown that the dominance of the $\beta \to \gamma$ over $\beta \to g$ matrix elements and the near equality of $\beta \to \gamma$ and $\gamma \to g$ $E2\mathrm{}$ matrix elements are inherent features of the model. The automatic inclusion of band mixing in the interacting boson approximation is discussed in terms of the mixing parameter $Z_{\gamma }$ and it is shown that the interacting boson approximation reproduces the empirical systematics in $Z_{\gamma }$. The concepts of the intrinsic state formalism are reviewed in the context of the consistent $Q$ framework and shown to imply vanishing $\beta \to g$ transitions, for any boson number, in the absence of $K$ mixing effects. The O(6) limit obtained with the consistent $Q$ formalism is shown to be a special case of the general limit. Finally, transition regions are discussed, particularly the SU(3)—O(6) case, in terms of "trajectories" in ${\chi }_Q$ between its limiting values. A number of qualitative parameter-free predictions for the evolution of energy or $E2\mathrm{}$ branching ratios are thus obtained.

NUCLEAR STRUCTURE Consistent $Q$ formalism of the IBA. Energy and $B\left(E2\mathrm{}\right)\mathrm{}$ predictions, contour plots, ${\chi }_Q$ trajectories, intrinsic state formalism.

The bound state Faddeev equations in the well-known simplified form for separable two-nucleon forces are extended to include a three-nucleon force. A numerical study for the two-pion-exchange three-nucleon force in conjunction with commonly used spin dependent $s$-wave $\mathrm{NN}$ forces is presented. The violent short-range behavior of the two-pion-exchange three-nucleon force requires the choice of form factors for the two-nucleon forces which have a repulsion built in.

NUCLEAR STRUCTURE Triton calculation, interplay of two- and three-nucleon force.

We have derived a two-pion-exchange three-body force and calculated its contribution to the trinucleon ground state. The hyperspherical harmonic method has been used. Coulomb and the three-body forces have been treated nonperturbatively. Results show sensitivity to the short range part of the force. A comparative study is made with other forms of three-body forces found in the literature.

NUCLEAR STRUCTURE Trinucleon systems, three-body force.

The changes in the nuclear structure of ${}_{}{}^{146-154}{}_{}{}^{}\mathrm{Sm}$ isotopes have been studied in the dynamic pairing-plus-quadrupole model. The overall variation in the energy of levels of $g$-, $\beta$-, and $\gamma$-vibrational bands; shape parameters; absolute $B\left(E2\mathrm{}\right)\mathrm{}$ values; $E0\mathrm{}$ moments; and $E2\mathrm{}$ branching ratios is given correctly. The effect of the change in the nature of the $2_2$ ($2_3$) state at $N\le 86$ on various transition moments is discussed. Increased asymmetry in lighter Sm isotopes is placed in the proper perspective. Comparison is made with other nuclear models.

NUCLEAR STRUCTURE Dynamic pairing-plus-quadrupole model, ${}_{}{}^{146-154}{}_{}{}^{}\mathrm{Sm}$, calculated level energies, static moments, $B\left(E2\mathrm{}\right)\mathrm{}$ values, and $E0\mathrm{}$ moments. Triaxiality.

The vector analyzing power for the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(\overrightarrow{\mathrm{d}}, \mathrm{p}){}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$ reaction has been measured at 4.0 MeV. Data for transitions to a number of states in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$ are compared with the results of distorted-wave Born approximation calculations. The $j$ dependence of the vector analyzing power is shown to persist in spite of the low bombarding energy and the presence of compound nucleus formation. The data for the 3.61 MeV state lead to a spin assignment of $j^{\pi }={\frac{1}{2}}^{-}$. The present results support the conclusion that this state is a close doublet.

NUCLEAR REACTIONS ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(\overrightarrow{\mathrm{d}}, \mathrm{p})$, $E_d=4.0\mathrm{}$ MeV; measured vector analyzing power $i{T}_{11}\left(\theta \right)$ for transitions to states in ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$ at $E_x=0.0, 1.94, 3.61, 3.94$ MeV. DWBA analysis.

Cross sections for (p, $x\mathrm{n}$), (p, $\mathrm{p}x\mathrm{n}$), and (p, $2\mathrm{p}x\mathrm{n}$) reactions of Ti, Fe, Co, Ni, Cu, and Zn isotopes at 12 GeV were determined from spallation yield data measured with a Ge(Li) $\gamma$-ray spectrometer. Among the measured cross sections which include associated pion production the (p, n) reactions show a large target dependence. The cross sections for ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$(p,n)${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$(p,n)${}_{}{}^{65}{}_{}{}^{}\mathrm{Zn}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$(p,n)${}_{}{}^{48}{}_{}{}^{}\mathrm{V}$, and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$(p,n)${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ are 14.9±2.4, 2.69±0.20, 1.64±0.26, and 0.58±0.04 mb, respectively.

NUCLEAR REACTIONS Ti, Fe, Co, Ni, Cu, Zn, (p, $x\mathrm{n}$), (p, $\mathrm{p}x\mathrm{n}$), (p, $2\mathrm{p}x\mathrm{n}$), reaction cross sections, $E=12\mathrm{}$ GeV, activation, target dependence.

Some comments are made on calculations with the generalized semimicroscopic model and a deformed configuration mixing shell model in the light of results obtained with a cluster-phonon model. Although the models yield a fairly good description of experimental data, a manifest discrepancy exists with these on the $B(E2; \frac{{}_{}{}^1{}_{}{}^{}3}{2}\to \mathrm{g}.\mathrm{s}.\mathrm{})$ values predicted by the generalized semimicroscopic and cluster-phonon models. There is also a difference in expected values for the nuclear deformation.

NUCLEAR STRUCTURE ${}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$; calculated levels, $J$, $\pi$, $B\left(E2\mathrm{}\right)\mathrm{}$, $B\left(M1\mathrm{}\right)\mathrm{}$, $q$, $\mu$, $S$, $b$, $\tau$. Cluster-phonon model; particle-hole excitations.

The quasielastic scattering of electrons on nuclei is reexamined in a coherent relativistic Fermi-gas description. The role of the scalar and vector potentials on the longitudinal and transverse response functions is discussed. Their momentum dependence is found to have important consequences.

NUCLEAR REACTIONS Quasielastic electron scattering. Longitudinal and transverse response functions. Effective mass. Effect of momentum dependence.

We discuss the relationship between recent estimates of the following three quantities: The imaginary part of the local optical-model potential, the mean free path of a nucleon, and the mean lifetime of a quasiparticle.

NUCLEAR REACTIONS Mean free path of a nucleon and imaginary part of the optical-model potential.

A procedure is outlined for estimating cross sections for neutron-induced spallation products relative to those for proton-induced reactions. When combined with known proton spallation systematics, it is demonstrated that cumulative yields for cosmogenically-important stable ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ and ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ isotopes are ∼1.4 and ∼2.8 times greater, respectively, for incident neutrons compared to protons at $0.2<~E<~3.0$ GeV for nearby medium mass targets. Yields for lighter kryptons are relatively insensitive to the identity of the incident nucleon.

NUCLEAR REACTIONS ($n$, spallation), $0.2<~E_n<~3.0$ GeV, stable Kr product yield estimates from proton spallation systematics.

Angular correlations of fragments from 292-MeV-${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$-induced fission of ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$, ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$, and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ have been measured. The correlations are interpreted in terms of a full linear momentum transfer component and several components with less than full momentum transfer. The maximum angular momentum $l_{\mathrm{FLMT}}$, associated with the full linear momentum transfer component from these and other previous angular correlation measurements, as well as from velocity measurements of evaporation residues, corresponds to rolling heavy ion collisions.

NUCLEAR REACTIONS Measured fission fragment angular correlations. Determined $l_{\mathrm{FLMT}}$ from the ${\sigma }_{\mathrm{FLMT}}$ of both fission and evaporation residues and compared results with rolling collisions.

The multiplicites of unresolved $\gamma$ rays depopulating low spin states in ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ have been measured for excitation energies up to the neutron binding energy. The general increase in multiplicity with excitation energy is well accounted for by a Fermi gas model. The comparison with theory shows that the dipole transition probabilities are not influenced by the giant dipole resonance.

NUCLEAR REACTIONS ${}_{}{}^{149}{}_{}{}^{}\mathrm{Sm}({}_{}{}^3{}_{}{}^{}\mathrm{He}, \alpha )$, $E=26\mathrm{}$ MeV; measured $\sigma \left(E_{\alpha }\right)$, $\gamma -\alpha$ coinc. ${}_{}{}^{148}{}_{}{}^{}\mathrm{Sm}$ deduced $\gamma$-ray multiplicity. Enriched target, Ge(Li), NaI(Tl), Si detectors. Fermi gas model analysis.

The level scheme of ${}_{}{}^{86}{}_{}{}^{}\mathrm{Zr}$ has been investigated experimentally and theoretically. Band crossings due to $g_{\frac{9}{2}}$ protons and neutrons as well as the second backbend in the yrast line have been observed. The triaxial cranked shell model has been applied in order to study the quasiparticle content of different bands and to determine the underlying nuclear shape.

Calculations for ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , \mathrm{p}){}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , \mathrm{n}){}_{}{}^3{}_{}{}^{}\mathrm{He}$ have been performed with the recoil-corrected continuum shell model. A charge-symmetry breaking interaction has been introduced in an effort to explain the large value (∼2) observed in recent experiments for the cross section ratio $R=\frac{\sigma (\gamma , \mathrm{p})}{\sigma (\gamma , \mathrm{n})}$. The calculations indicate that it is highly unlikely that such a large value of the cross section ratio can be obtained within standard theoretical assumptions.

NUCLEAR REACTIONS ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , \mathrm{p})$, ($\gamma , \mathrm{n}$), $E_x=20-36\mathrm{}$ MeV; calculated $\sigma \mathrm{}\left(E\right)\mathrm{}$, expansion coefficients $a_k\mathrm{}\left(E\right)\mathrm{}$, $B_k\mathrm{}\left(E\right)\mathrm{}$ for $\sigma (E, \theta )$, $P(E, \theta )$. ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(p,n); calculated $A\mathrm{}\left(E\right)\mathrm{}$, $P\left(E\right)\mathrm{}$. Studied influence of charge symmetry breaking interaction.

The proton capture cross sections to the ground and excited states of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have been measured at several angles in the proton energy interval between 18 and 40 MeV. The ground state angular distribution, which shows a significant $E1-E2\mathrm{}$ interference effect above 40 MeV, results in reasonable agreement with semidirect capture calculations. Transitions to final bound and unbound 1p-1h states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ having a dominant $1p_{\frac{1}{2}}^{-1\mathrm{}}$ hole have also been measured. Resonances built on these residual states have been systematically observed above $E_{\mathrm{p}}=20\mathrm{}$ MeV; the possible interpretation of these states as giant dipole resonances built on excited states is discussed.

NUCLEAR REACTIONS ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}(\mathrm{p}, {\gamma }_x){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Measured $\sigma \left(\theta \right)$ at seven angles and proton energies between 18 and 40 MeV; deduced $A_0$ and $a_k$ coefficients. Enriched gas target, anticoincidence NaI detector.