The activities ${}_{}{}^{101}{}_{}{}^{}\mathrm{Mo}$ and ${}_{}{}^{101}{}_{}{}^{}\mathrm{Tc}$ produced from neutron capture by natural Mo were chemically separated and studied using Ge(Li) $\gamma$-ray detectors. Out of 185 transitions observed in the decay of ${}_{}{}^{101}{}_{}{}^{}\mathrm{Mo}$, 170 were assigned to 44 excited levels in ${}_{}{}^{101}{}_{}{}^{}\mathrm{Tc}$. For the decay of ${}_{}{}^{101}{}_{}{}^{}\mathrm{Tc}$, 26 of 27 transitions were placed among 10 excited levels in ${}_{}{}^{101}{}_{}{}^{}\mathrm{Ru}$. The interpretation of the ${}_{}{}^{101}{}_{}{}^{}\mathrm{Tc}$ level scheme using the shell-model approach is not satisfactory even for a five-particle calculation. Systematics of odd-$A$ level structures in the region of $A=101\mathrm{}$ indicate that the level structure of ${}_{}{}^{101}{}_{}{}^{}\mathrm{Tc}$ could be due partly to the onset of collective effects.

RADIOACTIVITY ${}_{}{}^{101}{}_{}{}^{}\mathrm{Mo}$, ${}_{}{}^{101}{}_{}{}^{}\mathrm{Tc}$ [from natural $\mathrm{Mo}(n, \gamma )$]; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma -\gamma$ coin; deduced levels, $logft\text{'}\mathrm{s}$, $J$, $\pi$.

The low-spin level structure of ${}_{}{}^{106}{}_{}{}^{}\mathrm{Pd}$ was studied using high-resolution large volume Ge(Li) detectors for $\gamma$-ray singles, coincidence, and angular correlation measurements. The measurements allowed the resolution of most of the discrepancies found among previous studies. In particular, the use of two Ge(Li) detectors for coincidences and angular correlations allowed unambiguous placement of previously multiply placed $\gamma$ rays and resolved discrepancies in energy level or $J^{\pi }$ assignments. The experimental level structure and $B\left(E2\mathrm{}\right)\mathrm{}$ ratios are compared with predictions of an anharmonic spherical vibrator model and a rotor-vibrator model; we find that the evidence strongly supports the latter of the two models.

RADIOACTIVITY ${}_{}{}^{106}{}_{}{}^{}\mathrm{Pd}$ [from ${}_{}{}^{106}{}_{}{}^{}\mathrm{Rh}_{}^g{}_{}{}^{}$ decay]; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma -\gamma$ coin, $\gamma -\gamma$ angular correlations; Ge(Li) detectors; deduced $I_{\beta }$, $log\mathrm{ft}$, $J^{\pi }$ for ${}_{}{}^{106}{}_{}{}^{}\mathrm{Pd}$ levels; theory: energy levels and $B\left(E2\mathrm{}\right)\mathrm{}$ ratios, anharmonic spherical vibrator model and rotor-vibrator model.

The existence of a new isomeric state in ${}_{}{}^{110}{}_{}{}^{}\mathrm{Ag}$ at ∼ 1 keV excitation has been established in two experiments using a new instrument, the inner-shell-vacancy (ISV) detector. In the first experiment, a transition with a half-life of 660 ± 40 ns was observed to follow the well-known 116-keV $M4\mathrm{}$ transition that depopulates the $6^{+}$ 250-day isomeric level in ${}_{}{}^{110}{}_{}{}^{}\mathrm{Ag}$; the energy of the new transition was deduced to be <3.3 keV. In the second experiment, a half-life consistent with 660 ns was observed in the ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}(n, \gamma ){}_{}{}^{110}{}_{}{}^{}\mathrm{Ag}$ reaction to follow $\gamma$ transitions previously assigned by others to populate a 1-keV excited state. In combination the two results indicate the existence of a $2^{-}$ 660-ns isomer at 1.11 keV, although the (remote) possibility of more than one state near 1 keV cannot be excluded by direct experimental evidence. Under the assumption that the newly observed transition is from a $2^{-}$ 1.11-keV state to the $1^{+}$ ground state, its hindrance factor with respect to the Moszkowski estimate is ∼ 2.6 × ${10}^3$, within the range expected from systematics. Possible chemical-state perturbations of the measured half-life are estimated to be much smaller than the measurement error. In both experiments the ∼ 1-keV transition was detected with the ISV detector, a new device based on the well-established atomic effect that within ∼ ${10}^{-14\mathrm{}}$ s after the formation of an inner shell vacancy an atom will undergo a multiple loss of electrons ranging from several to 20 or more, the number being a function of $Z$ and subshell. The emitted electrons, which are very soft, are collected with an accelerating and focusing electrostatic lens and detected with a plastic scintillator and a photomultiplier tube. Nuclear transitions that cause ISVs can thus be sensed. Experiments are described that show the detector is fast, sensitive, selective, and efficient in responding to ISVs. It is primarily a timing device with very restricted suitability for determining the energy of an initiating nuclear transition.

RADIOACTIVITY ${}_{}{}^{110}{}_{}{}^{}\mathrm{Ag}_{}^m{}_{}{}^{}$; measured ce-ISV delayed coin; deduced new isomer $T_{\frac{1}{2}}$, $J$, $\pi$. Inner-shell-vacancy (ISV) detector.

NUCLEAR REACTIONS ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}(n, \gamma )$, $E=\mathrm{thermal}$; measured $E_{\gamma }$, $\gamma$-ISV delayed coin; deduced new isomer level. Inner-shell-vacancy (ISV) detector.

Some additional levels are proposed in the decay scheme of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Te}_{}^m{}_{}{}^{}$. From angular correlation and nuclear orientation measurements the spin and parity of several levels are determined uniquely: 774 keV (${\frac{11}{2}}^{+}$), 852 keV (${\frac{9}{2}}^{+}$), 1060 keV (${\frac{9}{2}}^{+}$), 1315 keV (${\frac{9}{2}}^{+}$), 1556 keV (${\frac{15}{2}}^{+}$), 1596 keV (${\frac{13}{2}}^{+}$), 1646 keV (${\frac{11}{2}}^{-}$), 1797 keV (${\frac{15}{2}}^{-}$), 1899 keV (${\frac{13}{2}}^{-}$), 1980 keV (${\frac{11}{2}}^{-}$), and 2001 keV (${\frac{9}{2}}^{\pm }$ or ${\frac{11}{2}}^{+}$). The $\delta \left(\frac{E2\mathrm{}}{M1\mathrm{}}\right)$ ratios for the different transitions are obtained. The magnetic moment of the ${}_{}{}^{131}{}_{}{}^{}\mathrm{Te}$ isomeric state is derived: $\mu =(-1.04\mathrm{}\pm 0.04){\mu }_N$.

RADIOACTIVITY ${}_{}{}^{131}{}_{}{}^{}\mathrm{Te}_{}^m{}_{}{}^{}$ from ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}(n, \gamma )$; measured $\gamma \gamma \left(\theta \right)$, $I_{\gamma }(\theta , T)$. ${}_{}{}^{131}{}_{}{}^{}\mathrm{I}$ deduced $J$, $n$, $\delta \left(\frac{E2\mathrm{}}{M1\mathrm{}}\right)$; ${}_{}{}^{131}{}_{}{}^{}\mathrm{Te}_{}^m{}_{}{}^{}$ deduced $\mu$. Ge(Li) detectors.

The neutron-rich isotope ${}_{}{}^{62}{}_{}{}^{}\mathrm{Fe}$ was discovered in a ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ metal foil irradiated in a new medium energy intense neutron beam at the Brookhaven 200-MeV linac. A flux in the energy range 25-200 MeV of ∼ 1.3 × ${10}^{11}$ n/${\mathrm{cm}}^2$ sec is obtained on target at this unique facility. The ${}_{}{}^{62}{}_{}{}^{}\mathrm{Fe}$ decays with a half-life of 68 ± 2 sec primarily by emission of 2.5-MeV $\beta$ rays to a $J^{\pi }=1^{+}$ level in ${}_{}{}^{62}{}_{}{}^{}\mathrm{Co}$ at 506.1 ± 0.1 keV.

RADIOACTIVITY ${}_{}{}^{62}{}_{}{}^{}\mathrm{Fe}$; measured $T_{\frac{1}{2}}$, $E_{\beta }$, $\beta \gamma$ coin; deduced $log\mathrm{ft}$ $Q$. ${}_{}{}^{62}{}_{}{}^{}\mathrm{Co}$; measured $E_{\gamma }$, $I_{\gamma }$; deduced levels $J$, $\pi$. Used medium energy intense neutron beam for ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}(n, 2pn)$.

The purpose of this paper is twofold. We calculate the parameters of the nuclear droplet model introduced by Myers and Swiatecki (an extension of the conventional liquid drop model) to higher powers of $A^{-\frac{1}{3}}$. We do Hartree-Fock (HF) calculations for a large number of spherical nuclei, using the modified $\delta$ interaction version of the Skyrme interaction and average over shell structure by making a least squares fit to the Hartree-Fock energies. We also compare the shell-averaged HF results with those obtained by using a simple version of the energy density formalism developed by Brueckner, Lombard, and others. We assume the simple form of the energy density first introduced by Skyrme for $N=Z$ nuclei, and minimize the total energy with respect to the actual density and diffuseness, subject to the constraint of fixed number of particles. Detailed comparison with the HF results was made for two $A=100\mathrm{}$ nuclei with $Z=50\mathrm{} \mathrm{and} 40$. We find that the droplet model energies calculated either exactly (numerically) or analytically by expansion of the radial integrals in powers of ($\frac{a}{R}$) ($a=\mathrm{diffuseness}$, $R=\mathrm{half}\mathrm{density}\mathrm{radius}\mathrm{for}\mathrm{a}\mathrm{Fermi}\mathrm{density}$) are in good agreement with the shell averaged HF results although there is some uncertainty in the latter. However, the central density is too small by about 10% for the cases considered. Yet, for the case $Z=40\mathrm{}$, $A=100\mathrm{}$, the ratio of neutron and proton densities is close to the Hartree-Fock value. Thus, we find the energy density formalism can reproduce quite closely the results of more complicated Hartree-Fock calculations.

NUCLEAR STRUCTURE Skyrme interaction, Hartree-Fock calculations, energy density formalism, nuclear surface.

Thin solid xenon targets were prepared by condensing xenon gas on iron at 4.2 K. First $2^{+}$ levels of ${}_{}{}^{124-132}{}_{}{}^{}\mathrm{Xe}$ were Coulomb excited and recoil implanted into the polarized iron foils. $B\left(E2\mathrm{}\uparrow \right)$ values and $g$ factors were determined from excitation and perturbed angular correlation data, respectively, and are in reasonable agreement with collective model calculations. A value for the average hyperfine field on xenon implanted into iron under these experimental conditions was determined to be $H_{\mathrm{eff}}=1.40\mathrm{}\pm 0.37$ MOe.

NUCLEAR STRUCTURE ${}_{}{}^{124-132}{}_{}{}^{}\mathrm{Xe}$, $2^{+}$levels Coulomb excited, 36-42 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, $W\left(\theta \right)$, deduced $B\left(E2\mathrm{}\uparrow \right)$, $g$ factors, $H_{\mathrm{eff}}$ Xe (Fe).

The $n$-pion-exchange ($n+1\mathrm{}$)-body force is written explicitly in coordinate space and separated into its central and tensor parts. Exchanges of the spectator nucleons are shown to cause large cancellations. The ratio of $n$-body forces to ($n+1\mathrm{}$)-body forces is estimated and compared with recent three- and four-body calculations.

NUCLEAR STRUCTURE Nuclear many body forces; calculated effective two-body potential; includes correlations; estimated convergence ratio; calculated effect of spectator exchanges.

The use of an on-line mass spectrometer to make direct mass measurements of short-lived isotopes far from the stability line has been improved to yield more accurate mass measurements for ${}_{}{}^{27-30}{}_{}{}^{}\mathrm{Na}$, new mass measurements for ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{31,32}{}_{}{}^{}\mathrm{Na}$, and to remove a discrepancy between existing mass measurements of ${}_{}{}^{26}{}_{}{}^{}\mathrm{Na}$. The mass excesses (keV) measured are: ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$, 40940±80; ${}_{}{}^{26}{}_{}{}^{}\mathrm{Na}$, -6901±25; ${}_{}{}^{27}{}_{}{}^{}\mathrm{Na}$, -5620±60; ${}_{}{}^{28}{}_{}{}^{}\mathrm{Na}$, -1140±80; ${}_{}{}^{29}{}_{}{}^{}\mathrm{Na}$, 2650±100; ${}_{}{}^{30}{}_{}{}^{}\mathrm{Na}$, 8370±200; ${}_{}{}^{31}{}_{}{}^{}\mathrm{Na}$, 10600±800; ${}_{}{}^{32}{}_{}{}^{}\mathrm{Na}$, 16400±1100. The ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ value indicates that it is bound by only 170±80 keV. The masses of ${}_{}{}^{31}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{Na}$ imply that these nuclei are more tightly bound than expected from theoretical predictions.

NUCLEAR STRUCTURE ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{26-32}{}_{}{}^{}\mathrm{Na}$; measured atomic masses. On-line mass spectrometer.

RADIOACTIVITY ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$; deduced $log\mathrm{ft}$.

The compound resonances and the bound states observed in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+nucleon system are studied using the continuum shell model. The method of solution involves a division of configuration space as in the $R$-matrix theory. Shell model basis states which are eigenfunctions of the spherical harmonic oscillator potential are employed in the construction of trial wave functions for the internal region. The basis states contain active $1p_{\frac{1}{2}}$, $1d_{\frac{5}{2}}$, and $2s_{\frac{1}{2}}$ orbits as well as higher orbits into which at most a single nucleon is placed. Excitations of up to four particles from the spherical closed core are included. The two-body interaction used in our model was taken from a shell model calculation for ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ by Zuker, supplemented by a two-body central Gaussian interaction from True and a one-body interaction of Woods-Saxon form. Calculated neutron total cross sections, neutron and proton phase shifts as well as differential cross sections and polarizations are presented and compared with experiment. Calculated spectroscopic factors of ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ states are also given. The results show excellent qualitative and fair quantitative agreement with experiment. An investigation of the discrepancies between calculated and experimental resonance widths point to our lack of knowledge of the effective interaction.

NUCLEAR STRUCTURE, REACTIONS ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$; calculated bound and continuum eigenstates, $J$, $\pi$, $\Gamma$, $S$. ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}(n, n)$, $E<\mathrm{}4\mathrm{}$ MeV, ($p, p$), $E<\mathrm{}6\mathrm{}$ MeV; calculated phase shifts, $\sigma \mathrm{}\left(E\right)\mathrm{}$, $P\left(E\right)\mathrm{}$. Continuum shell model, $R$-matrix discretization.

Employing the Hartree-Fock-Bogoliubov approximation and the Kuo-Brown interaction, results for odd-mass nuclei in the $0f-1p$ shell are reported. A ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ core has been assumed. The blocking effect due to the presence of the odd nucleon has been taken into account. The ground-state energies, the intrinsic and ground-state quadrupole moments, reduced transition rates, and the pickup strengths are calculated and compared with the corresponding available experimental values.

NUCLEAR STRUCTURE Odd isotopes of Ti, Cr, Fe, Ni, Zn, Ge, V, Mn, Co, Cu, Ga, As; calculated single-particle binding energies, ground-state energies, intrinsic and ground-state quadrupole moments, reduced transition rates, pickup strengths. Hartree-Fock-Bogoliubov method. Kuo-Brown interaction.

The response of a many-fermion system to dilatation is studied through the introduction, in close analogy with the "cranking" and "pushing" models, of a "squashing" model characterized by the Hamiltonian, $H=H_0-\dot{\epsilon }{D}_x$, where $D_x$ is the generator of dilatations in the $x$ direction. The evaluation of the "rigid" dilatational moment of such a noninteracting system is carried out for both standing wave and periodic boundary conditions in a cubic box of side $L$. As in the pushing model, the dilatation moment can be evaluated formally using the relation between $D_x$ and the commutator [$x^2$, $H_0$]. For independent fermions moving in a harmonic oscillator one-body potential, this relation is shown to lead to further simplification after the introduction of perturbed one-body wave functions. In the case of periodic boundary conditions, it is shown that the rigid dilatational moment is not altered by an interparticle interaction to first order in the interaction strength; by comparison with the analogous cranking moment problem, this result extends to all orders in the interaction strength. The response to a symmetric dilatation, $D=D_x+D_y+D_z$, is studied in a soluble Hartree model of "nuclear" correlations wherein a separable monopole-monopole interaction acts between "nucleons." In this model the dilatation moment in the presence of pair correlations is found to be the rigid moment, with the kinetic energy of dilatation $\propto {\dot{\epsilon }}^2$, there being no higher order corrections.

NUCLEAR STRUCTURE Approximate many-body methods applied to solvable models.

The observed differences in the neutron-evaporation excitation functions for argon- and krypton-induced reactions may be due to the strong friction in the classical dynamic model. In order to reproduce the complete fusion cross sections, a large energy loss in the Kr entrance channel is needed. This large energy loss may be associated with the preequilibrium emission of neutrons in the Kr channel. Neither the large energy loss nor the preequilibrium emission is expected in the Ar channel.

NUCLEAR REACTIONS ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ge}(\mathrm{Kr}, xn)$; ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}(\mathrm{Ar}, xn)$. Evaporation residues analyzed with classical model.

This paper deals with the problem of various deep processes occurring when two complex nuclei enter in collision. It is suggested that very deep inelastic processes may lead to either a compound nucleus or a composite system which shortly decays into two fission fragments (quasifission process). Particularly for heavy projectiles and targets, the predominant Coulomb potential inhibits the compound nucleus formation for low $l$ waves. Then a critical angular momentum can be defined as the limit below which both processes (quasifission and compound nucleus formation) occur. For the heaviest nuclei, nearly all $l$ waves below $l_{\mathrm{cr}}$ contribute to the quasifission phenomenon.

NUCLEAR REACTIONS Ar, Cu, Kr ions; discussed $\sigma$ complete and incomplete fusion.

The parametrization of total muon capture rates in terms of a mean nuclear excitation energy ${\overline{E}}^{\prime }$, recently proposed by Christillin, Dellafiore, and Rosa-Clot, is reexamined in view of recent criticisms. The previously obtained results are reconfirmed.

NUCLEAR REACTIONS ${\mu }^{-}+A(N, Z)\to \nu +A(N+1, Z-1)$; muon capture; closure approximation; mean nuclear excitation energies.

An alternative approach to the recent results of Krajcik and Foldy is presented which stresses a different point of view, but is completely equivalent to their results.

NUCLEAR REACTIONS Relativistic corrections to wave functions.

An investigation of the $\mathrm{Ll}$ x-$\gamma$ angular correlations following the decay of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ is done by using a Si(Li) semiconductor counter as $L$ x-ray detector. Coincidence measurements at five different angles were made between the 570-keV $\gamma$ ray (gated in the movable counter) and the $\mathrm{Ll}$ x spectrum (displayed in a multichannel analyzer).

RADIOACTIVITY ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$, measured $\mathrm{Ll}$ X- $\gamma \left(\theta \right)$, deduced anisotropy. Si(Li) detector, 500 eV at 10 keV.

From the analysis of the $K$ x-ray—$\gamma$-ray sum peaks observed with a Ge(Li) detector the $K$-capture probability ($P_K$) for the 1529.8 keV and 1233.8 keV states of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Sm}$ in the decay of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Eu}$ (12.4 yr) and 690.5 keV state of ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$ in the decay of ${}_{}{}^{192}{}_{}{}^{}\mathrm{Ir}$ (74 day) have been determined. The observed values are: $P_K^{1529.8}=0.76\mathrm{}\pm 0.09$, $P_K^{1233.8}=0.88\mathrm{}\pm 0.10$ and $P_K^{690.5}=0.70\mathrm{}\pm 0.06$.

RADIOACTIVITY ${}_{}{}^{152}{}_{}{}^{}\mathrm{Eu}$, ${}_{}{}^{192}{}_{}{}^{}\mathrm{Ir}$; measured sum-peak areas, $I_{\gamma }$, $I_{K\mathrm{x}}$; deduced $P_K$.

By observation of the resonant scattering of bremsstrahlung, the width of the 2.31-MeV level of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ has been measured as 6.2 ± 0.6 meV. This is somewhat smaller than previous values and in disagreement with inelastic electron scattering results and the prediction of the conserved vector current theory from the shape of the ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ → ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ${\beta }^{+}$ spectrum.

NUCLEAR REACTIONS ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(\gamma , \gamma )$, $E=2.31\mathrm{}$ MeV; measured $\sigma \left(96\mathrm{}°\right)$ and $\sigma \left(126\mathrm{}°\right)$; deduced $\Gamma$; natural target.

The ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}(d, p){}_{}{}^{69}{}_{}{}^{}\mathrm{Zn}$ reaction has been studied with an incident deuteron bombarding energy of 7.5 MeV. A total of 48 levels below $E_x=4.8\mathrm{}$ MeV have been identified in ${}_{}{}^{69}{}_{}{}^{}\mathrm{Zn}$.

NUCLEAR REACTIONS ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}(d, p)$, ($d, d$), $E_d=7.5\mathrm{}$ MeV; measured $\sigma (E_p, \theta )$, $Q$. ${}_{}{}^{69}{}_{}{}^{}\mathrm{Zn}$ deduced levels, $J$, $\pi$, $l_n$. Enriched target.