Energy correlation measurements were performed for the spontaneous fission of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ and its photofission with 12-, 15-, 20-, and 30-MeV bremsstrahlung. The photofission cross section for ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ was deduced from a measured yield curve up to 30 MeV using the photon difference method. A comparison of the $〈E_k^{*}〉\left(m^{*}\right)$ behavior for spontaneous and photon induced fission shows that the observed decrease with increasing compound nucleus excitation energy of the average total kinetic energy release is caused predominantly by changes in the total deformation of the fragments for the mass splits with the heavy fragment mass in the vicinity of the closed $N=82\mathrm{}$ neutron shell. Comparing the fissioning systems ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ and ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$, the difference, ${〈E_k^{*}〉}_{\mathrm{sf}}-{〈E_k^{*}〉}_{\gamma }$, between spontaneous and photon induced fission is 3 MeV larger for the former system. The $〈E_k^{*}〉\left(m_H^{*}\right)$ curves for ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$ (sf) and ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ (sf) are parallel at a distance of about 3 MeV. The mass distribution for photon induced fission of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$ compared to spontaneous fission shows a decreased peak yield, a broadening of the mass distribution peaks, and a shift of the peaks over 3 mass units towards asymmetry. Comparing the fissioning systems ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$ and ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$, the heavy fragment peak remains practically constant in position for both spontaneous and photon induced fission.

RADIOACTIVITY, FISSION ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$(sf).

NUCLEAR REACTIONS, FISSION ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}(\gamma , f)$, ${E_{\gamma }}_{max}=12, 15, 20, 30$ MeV; measured photofission yields, fragment energies $E_1$, $E_2$; deduced $\sigma (\gamma , f)$, $\frac{N(\mu , E_k)}{〈E_{\mathrm{exc}}\left(E_e\right)〉}$.

The pion double charge exchange reactions, ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({\pi }^{+}, {\pi }^{-}xn){}_{}{}^{209-x}{}_{}{}^{}\mathrm{At}$, have been studied by radiochemical techniques for incident pion energies of 100, 180, and 300 MeV. Cross sections for the chemically separated At isotopes $A=205-209\mathrm{}$ were determined by alpha-particle and gamma-ray spectroscopy. The contribution of secondary processes, such as ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({\pi }^{+}, {}_{}{}^{3,4}{}_{}{}^{}\mathrm{He})X$ followed by ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({}_{}{}^4{}_{}{}^{}\mathrm{He}, xn){}_{}{}^{213-x}{}_{}{}^{}\mathrm{At}$ and ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({}_{}{}^3{}_{}{}^{}\mathrm{He}, xn){}_{}{}^{212-x}{}_{}{}^{}\mathrm{At}$, which mimic the double charge exchange process, was evaluated through a study of the ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({\pi }^{-}, X)\mathrm{At}$ reactions, since double charge exchange channels cannot contribute to At production in such ${\pi }^{-}$ interactions. Such secondary reactions were further characterized through target thickness studies employing 100-300 MeV ${\pi }^{-}$ beams. An upper limit of the cross sections for ${}_{}{}^{209}{}_{}{}^{}\mathrm{At}$ production via elastic or inelastic double charge exchange below particle emission thresholds was determined to be 6 μb—a result which is roughly consistent with independent spectrometer measurements. Double charge exchange processes in which 8-50 MeV of excitation energy remains in ${}_{}{}^{209}{}_{}{}^{}\mathrm{At}$ (to be later dissipated by neutron evaporation) are found to be much more probable as evidenced by the ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({\pi }^{+}, {\pi }^{-}xn){}_{}{}^{209-x}{}_{}{}^{}\mathrm{At}$, $x=2-4\mathrm{}$ excitation functions which are seen to be strongly and inversely dependent on the incident pion energy.

NUCLEAR REACTIONS ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({\pi }^{+}, {\pi }^{-}xn){}_{}{}^{209-x}{}_{}{}^{}\mathrm{At}$, $E_{{\pi }^{+}}=100-300\mathrm{}$ MeV; ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({\pi }^{-}, X){}_{}{}^{207-211}{}_{}{}^{}\mathrm{At}$, $E_{{\pi }^{-}}=100-300\mathrm{}$ MeV; measured $\sigma \mathrm{}\left(E\right)\mathrm{}$, deduced secondary contributions; alpha particle and $\gamma$-ray spectroscopy, Si and Ge(Li) detectors, high purity targets, carrier-free radiochemistry.

The inelastic scattering of 162-MeV pions by ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ has been studied over the angular range 35° to 115° in the laboratory system. The data were analyzed with a model which incorporates shell model wave functions into a distorted wave impulse approximation. Reduced transition probabilities obtained for a number of low-lying states are compared to previous data to validate the model. Among new assignments and shell model descriptions presented for several higher excited states is an assignment for the yrast $5^{-}$ state.

NUCLEAR REACTIONS ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(\pi , {\pi }^{\prime })$ $E_{\pi }=162\mathrm{}$ MeV, measured $\sigma \left(\theta \right)$, melamine target, DWIA analysis.

Excitation functions have been determined for the formation of ten iodine nuclides (${}_{}{}^{117}{}_{}{}^{}\mathrm{I}$—${}_{}{}^{126}{}_{}{}^{}\mathrm{I}$) in the interaction of 60-350 MeV ${\pi }^{+}$ and ${\pi }^{-}$ with ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$. The contribution of various reaction mechanisms has been estimated from the systematic features of the excitation functions and isotopic yield distributions with the aid of cross sections obtained for the production of various isobaric xenon nuclides, cross-section results for 500 MeV proton bombardment of ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$, and comparison with Monte Carlo cascade-evaporation calculations. It is found that, with varying importance, mechanisms involving direct neutron knockout, pion inelastic scattering plus evaporation, pion absorption, and pion charge exchange contribute to the observed yields.

NUCLEAR REACTIONS ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}({\pi }^{\pm }, {\pi }^{\pm }xn)$, $x=1-10\mathrm{}$, excitation functions (activation), $T_{\pi }=60-350\mathrm{}$ MeV. KI targets. Deduced reaction mechanisms.

Fuda's method to construct a $\pi N$ separable model for the $P$ wave interaction is extended to further include the inelasticity effect for all partial waves and the sign changing property of the $P_{11}$ phase shift.

NUCLEAR REACTIONS $\pi N$ $P$ wave separable model, inverse scattering problem with crossing symmetry; $t$ matrix contains nucleon poles, right and left cuts, and inelasticity effect; $P_{11}$ changes the sign.

The photoproduction of neutral pions is studied in the distorted wave impulse approximation. The cross sections are calculated for pion production from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and are found to be in good agreement with the available data. The present results compare well with the theoretical calculations carried out in the framework of the isobar-doorway model.

NUCLEAR REACTIONS ${\pi }^0$ photoproduction from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$; distorted wave impulse approximation.

We evaluate the weak magnetism and other higher order matrix elements for the beta decays of ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$, ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$, and ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$. The matrix elements were obtained from $\mathrm{sd}$ shell-model wave functions derived from the one- and two-body effective interactions of Chung and Wildenthal. The shapes of the beta spectra are calculated assuming zero-mass neutrinos and allowing for the higher order matrix elements. The calculations suggest that precise measurements of these spectra would be useful to search for heavy neutrinos with intensities of the order of > ${10}^{-3\mathrm{}}$ over the neutrino mass range from 20 keV to 2 MeV. While other observations may rule out such parameters for mixing of massive neutrinos, the measurements of spectra would provide the most direct and least uncertain limits. For the allowed decays of ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ and ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ the weak magnetism form factor appears to be the dominant higher order effect. The analog $M1\mathrm{}$ matrix elements are known experimentally in both cases and thus the weak magnetism terms are determined through the conserved vector current theory. One might alternatively regard measurements of these spectra as tests of the conserved vector current predictions.

RADIOACTIVITY ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$, ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$; calculated nuclear matrix elements, shapes of beta spectra. Relationship to searches for heavy neutrinos.

The isotope ${}_{}{}^{156}{}_{}{}^{}\mathrm{Yb}$ was produced via the ${}_{}{}^{147}{}_{}{}^{}\mathrm{Sm}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, 7n)$ reaction and was mass separated with an on-line isotope separator. Its decay properties were studied by using $\gamma$-ray, x-ray, and $\alpha$-particle detectors. The half-life and $\alpha$ decay energy extracted were found to agree with values from earlier $\alpha$-decay investigations. In addition, the (EC+${\beta }^{+}$) decay of ${}_{}{}^{156}{}_{}{}^{}\mathrm{Yb}$ was identified for the first time. This decay to ${}_{}{}^{156}{}_{}{}^{}\mathrm{Tm}$ is accompanied by only one strong $\gamma$ ray, an $E1\mathrm{}$ transition of 115.2±0.2 keV. It is proposed that, as in the case of the ${}_{}{}^{148,150,152}{}_{}{}^{}\mathrm{Dy}$ decays to odd-odd terbium nuclei, essentially all of the ${}_{}{}^{156}{}_{}{}^{}\mathrm{Yb}$ $\beta$ decay proceeds to a $1^{+}$ level in ${}_{}{}^{156}{}_{}{}^{}\mathrm{Tm}$ at ∼ 115 keV by an allowed transition, $log\mathrm{ft}\sim 3.9$. This $1^{+}$ level then depopulates to a $2^{-}$ at or near the ground state. Alpha-decay branching ratios were deduced for ${}_{}{}^{156}{}_{}{}^{}\mathrm{Yb}$, ${}_{}{}^{156}{}_{}{}^{}\mathrm{Tm}$, ${}_{}{}^{152}{}_{}{}^{}\mathrm{Er}$, and ${}_{}{}^{152}{}_{}{}^{}\mathrm{Ho}$.

RADIOACTIVITY ${}_{}{}^{156}{}_{}{}^{}\mathrm{Yb}$, ${}_{}{}^{156}{}_{}{}^{}\mathrm{Tm}$, ${}_{}{}^{152}{}_{}{}^{}\mathrm{Er}$, ${}_{}{}^{152}{}_{}{}^{}\mathrm{Ho}$ [from ${}_{}{}^{147}{}_{}{}^{}\mathrm{Sm}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, 7n)$] measured $T_{\frac{1}{2}}$, $E_{\alpha }$, $I_{\alpha }$, $E_{\gamma }$, $I_{\gamma }$, $I_x$; deduced $log\mathrm{ft}$, spins, parities, multipolarities, $\alpha$-branching ratios. Mass-separated samples, enriched target.

The neutron separation energy of ${}_{}{}^{34}{}_{}{}^{}\mathrm{S}$ and the proton separation energy of ${}_{}{}^{34}{}_{}{}^{}\mathrm{Cl}$ have been measured accurately via the ${}_{}{}^{33}{}_{}{}^{}\mathrm{S}(n, \gamma ){}_{}{}^{34}{}_{}{}^{}\mathrm{S}$ and the ${}_{}{}^{33}{}_{}{}^{}\mathrm{S}(p, \gamma ){}_{}{}^{34}{}_{}{}^{}\mathrm{Cl}$ reactions. The measured values imply a $Q$ value of 5492.48±0.20 keV for the total decay energy of ${}_{}{}^{34}{}_{}{}^{}\mathrm{Cl}$ if the calibration is based on the "mass doublet standard" and a $Q$ value of 5492.42±0.23 keV if based on the 411.8044±0.0011 keV line in ${}_{}{}^{198}{}_{}{}^{}\mathrm{Au}$. If the conserved vector current hypothesis is valid and the electromagnetic corrections are made properly, the $\mathrm{ft}$ values for superallowed $0^{+}$→$0^{+}$ $\beta$ decays should all be the same. The $\mathrm{ft}$ values for the superallowed ${}_{}{}^{34}{}_{}{}^{}\mathrm{Cl}$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ decays were found to be equal to better than (4±16) parts in ${10}^4$, in agreement with the expectations.

NUCLEAR REACTIONS ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{33}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{34}{}_{}{}^{}\mathrm{S}(n, \gamma )$, $E=\mathrm{thermal}$; measured $E_{\gamma }$. ${}_{}{}^{33}{}_{}{}^{}\mathrm{S}$,${}_{}{}^{34}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$ deduced neutron separation energy. ${}_{}{}^{33}{}_{}{}^{}\mathrm{S}$, ${}_{}{}^{34}{}_{}{}^{}\mathrm{S}(p, \gamma )$, $E=0.9-1.4\mathrm{}$ MeV; measured $E_{\gamma }$. ${}_{}{}^{34}{}_{}{}^{}\mathrm{Cl}$, ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ deduced resonances, proton separation energy.

RADIOACTIVITY ${}_{}{}^{34}{}_{}{}^{}\mathrm{Cl}$, ${}_{}{}^{35}{}_{}{}^{}\mathrm{S}$, deduced $Q$. ${}_{}{}^{34}{}_{}{}^{}\mathrm{Cl}$, deduced $\mathrm{ft}$.

A basic formalism is developed for the theory of the effect on nuclear beta decay of an intense, plane-wave electromagnetic field. Interactions of the field with both the nuclear particles and the decay electron are included. The formalism is developed from first principles, including a derivation of transition probabilities between explicitly time-dependent asymptotic states. Interaction of the field with the nucleus is analyzed in terms of separation of the nucleus into an inert core and a fragment. The field interacts with the fragment, consisting of the nucleons which are candidates for beta decay, plus any other nucleons angular-momentum coupled to them in initial or final states. A separation of variables in the dynamical equations for the nucleus into center-of-mass and relative coordinates for the core and fragment shows direct charge coupling even for a fragment consisting entirely of neutrons. The transition formalism involves specific intense-field wave functions both for the nucleus and for the beta particle. Complete results are presented for total transition probability per unit time for intense-field-coupled nuclear beta decay. A much simplified formalism is given for the special case of very high field intensity at very low frequency. The results then bear a formal resemblance to ordinary beta decay theory, but they contain specific field effects in the beta particle spectral function, and in the nuclear interaction matrix elements. This is the first of a series of papers on this subject.

RADIOACTIVITY Intense-field-induced $\beta$ decay. $\beta$ decay forbiddenness removal.

A formalism developed earlier for the effect on nuclear beta decay of an intense planewave electromagnetic field is applied to three examples of forbidden beta transitions. The examples represent cases where the nuclear "fragment" contains one, two, and three nucleons; where the nuclear fragment is defined to be that smallest sub-unit of the nucleus containing the nucleon which undergoes beta decay plus any other nucleons directly angular-momentum coupled to it in initial or final states. The single-nucleon-fragment example is ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$, which has a fourth-forbidden transition. The two-nucleon-fragment example is ${}_{}{}^{90}{}_{}{}^{}\mathrm{Sr}$, which is first-forbidden. The three-nucleon-fragment example is ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$, which is third-forbidden. An algebraic closed-form transition probability is found in each case. At low external-field intensity, the transition probability is proportional to $z^L$, where $z$ is the field intensity parameter and $L$ is the degree of forbiddenness. At intermediate intensities, the transition probability behaves as $z^{L-\left(\frac{1}{2}\right)}$. At higher intensities, the transition probability contains the $z^{L-\left(\frac{1}{2}\right)}$. factor, a declining exponential factor, and an alternating polynomial in $z$. This high-intensity transition probability possesses a maximum value, which is found for each of the examples. A general rule, $z=q^2\mathrm{}(2L-1)\mathrm{}$, where $q$ is the number of particles in the fragment, is found for giving an upper limit on the intensity at which the maximum transition probability occurs. Field-induced beta decay half-lives for all the examples are dramatically reduced from natural half-lives when evaluated at the optimum field intensity. Relative half-life reduction is greater the higher the degree of forbiddenness.

RADIOACTIVITY ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Sr}$, ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ intense-field-induced $\beta$ decay minimum half-lives, half-life reduction forbiddenness dependence.

We have used the $\beta -\gamma$ circular polarization correlation technique to measure the isospin-forbidden Fermi matrix element for the ${\beta }^{+}$ decay of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ to the $4^{+}$ $T=1\mathrm{}$ state in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ at $E_x=8.439\mathrm{}$ MeV. The ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ activity was produced by bombarding a natural Mg target with 18 MeV protons. The $\beta -\gamma$ circular polarization correlation was measured using a novel apparatus which featured good energy resolution in both the $\gamma$ and $\beta$ arms. The circular polarization sensitive $\gamma$-ray detector utilized a transmission-mode Compton polarimeter and a 12.7 cm × 15.2 cm NaI detector. The $\beta$ detector was a telescope with a 700 μm surface barrier detector and a 5.1 cm × 12.7 cm plastic scintillator. The $\beta -\gamma$ circular polarization asymmetry $\tilde{A}$ [defined by $W(\theta , \tau )=1+\frac{\tau v}{c\tilde{A}}cos\theta$ where $\tau$ is the photon helicity] was found to be $\tilde{A}=-0.145\mathrm{}\pm 0.030$. After applying a correction for feeding of the 8.439 MeV state from the analog state this value of $\tilde{A}$ corresponds to a charge dependent matrix element between the 9.5 MeV $4^{+}$ $T=1\mathrm{} \mathrm{and} 8.4$ MeV $T=0\mathrm{}$ levels of $|〈4^{+}; 0|H_{\mathrm{CD}}|4^{+}; 1〉|=106\mathrm{}\pm 40$ keV which is the largest matrix element of $H_{\mathrm{CD}}$ ever observed in $\beta$ decay. For comparison the charge dependent matrix element between the 9.5 MeV state and the 4.1 MeV $4^{+}$ state, previously measured in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ decays is only 5.4±2.2 keV. Our exceptionally large value occurs because the 9.5 MeV $T=1\mathrm{} \mathrm{and} 8.4$ MeV $T=0\mathrm{}$ states have very similar space and spin wave functions. This matrix element is consistent with predictions which ascribe the entire effect to Coulomb forces.

RADIOACTIVITY ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ [from ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(p, n)$]; measured $\beta \gamma$ CP correlations; developed new apparatus; measured isospin forbidden Fermi matrix element. Deduced isospin mixing matrix element.

We have calculated the probability of a process in which internal bremsstrahlung associated with $K$ electron capture in an allowed transition is accompanied by the simultaneous ejection of the uncaptured $K$ electron. Consideration has been given to the case where the ejected electron is produced by the sudden change in the nuclear Coulomb field in the capture process, and to ejection produced by interactions between the two $K$ electrons. The relative importance of the respective contributions is discussed.

RADIOACTIVITY Calculated simultaneous IB and autoionization in EC; ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ar}$, ${}_{}{}^{55}{}_{}{}^{}\mathrm{Fe}$.

A previously unreported isotope, ${}_{}{}^{165}{}_{}{}^{}\mathrm{Tb}$, has been identified, and its half-life has been measured to be 2.11±0.10 min. This activity was observed in the Tb fraction separated, using a high-performance liquid chromatograph, from the fission products resulting from spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$. Some 24 $\gamma$ rays have been associated with the ${}_{}{}^{165}{}_{}{}^{}\mathrm{Tb}$ decay, ∼16 of which have been placed in a level scheme for ${}_{}{}^{165}{}_{}{}^{}\mathrm{Dy}$. New features of the ${}_{}{}^{165}{}_{}{}^{}\mathrm{Dy}$ level scheme are excited states at 1337.1, 1400.2, 1773.1, and possibly 1813.7 keV, which are fed by $\beta$ transitions with $log\mathrm{ft}$ values between 5.1 and 5.7. Configuration assignments for these states are discussed.

RADIOACTIVITY ${}_{}{}^{165}{}_{}{}^{}\mathrm{Tb}$, measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$; ${}_{}{}^{165}{}_{}{}^{}\mathrm{Dy}$ deduced levels $J$, $\pi$, $log\mathrm{ft}$. Radiochemical separation, Ge(Li) detectors.

Inner bremsstrahlung accompanying electron-capture decay of ${}_{}{}^{49}{}_{}{}^{}\mathrm{V}$ has been measured with a (4.5×5.1)-cm NaI(Tl) scintillation spectrometer in the energy region 180-580 keV. The counts spectrum was unfolded following the procedure of Lidén and Starfelt. Results were compared with the ($1s+2s$)-capture relativistic calculations of Martin and Glauber. At energies higher than 340 keV, the shape of the spectrum agrees with the predictions of the theory. At energies less than 340 keV, experimental values are lower than the theoretical values.

RADIOACTIVITY ${}_{}{}^{49}{}_{}{}^{}\mathrm{V}$ measured IB ($1s+2s$); NaI(Tl) detector; spectrum shape.

The probability for $K$-shell electron shakeoff in the positron decay of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$ has been measured by recording coincidences between the annihilation radiation produced subsequent to the positron decay and the Fe $K$ x rays produced when the $K$-shell vacancy is filled. This probability was found to be (13.8±2.4)×${10}^{-4\mathrm{}}$, which is approximately 2 times larger than recent theoretical predictions by Law and Suzuki.

RADIOACTIVITY Measured Fe $K$ x rays in coincidence with annihilation photons produced in ${\beta }^{+}$ decay of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$; deduced $K$-shell electron shakeoff probability.

The nuclear structure of the low lying levels of the transitional nucleus ${}_{}{}^{147}{}_{}{}^{}\mathrm{Eu}$, from ${}_{}{}^{147}{}_{}{}^{}\mathrm{Gd}$ decay, has been investigated by $\gamma -\gamma$ directional correlation experiments using a Ge(Li)-Ge(Li) fast coincidence arrangement. From the measurements on the 396-229.3, 549.5-229.3, 632.8-229.3, 766.0-229.3, 893.4-229.3, 1006.6-229.3, 1131.0-229.3, 1325.1-229.3, 1587.4-229.3, 240.6-370, 249.2-370, and 559.1-370 keV cascades, spin-parity assignments of ${\frac{5}{2}}^{+}$, ${\frac{7}{2}}^{+}$, ${\frac{11}{2}}^{-}$, ${\frac{7}{2}}^{+}$, ${\frac{7}{2}}^{+}$, ${\frac{9}{2}}^{-}$, ${\frac{7}{2}}^{+}$, ${\frac{7}{2}}^{-}$, ${\frac{7}{2}}^{-}$, ${\frac{9}{2}}^{-}$, ${\frac{9}{2}}^{-}$, and ${\frac{5}{2}}^{+}$ have been made to the ground, 229.3, 625.3, 778.2, 861.7, 995.3, 1122.9, 1235.9, 1244.5, 1360.3, 1554.5, and 1816.6 keV states of ${}_{}{}^{147}{}_{}{}^{}\mathrm{Eu}$, respectively. These spin-parity assignments are unique since they are measured by different cascade branchings. The results have been discussed and compared with previous works.

RADIOACTIVITY ${}_{}{}^{147}{}_{}{}^{}\mathrm{Gd}$; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma \left(\theta \right)$, coin.; ${}_{}{}^{147}{}_{}{}^{}\mathrm{Eu}$ levels deduced, $J$, $\pi$; Ge(Li) detectors.

The strengths of transitions in $A=24\mathrm{}$ between $J^{\pi }=1^{+}$, $T=1\mathrm{}$ states and the lowest $J^{\pi }=0^{+}$ states of $T=0\mathrm{} \mathrm{and} 2$ are calculated from shell-model wave functions constructed in the full eight-particle $0d_{\frac{5}{2}}-1\mathrm{}{s}_{\frac{1}{2}}-0\mathrm{}{d}_{\frac{3}{2}}$ configuration space. The model Hamiltonian is an empirical interaction which yields a good accounting of the energies of intra-$\mathrm{sd}$-shell states throughout the $A=17-39\mathrm{}$ region. With these same wave functions the ($e, e^{\prime }$) form factors for the magnetic dipole excitation of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ to its lowest five states of $J^{\pi }=1^{+}$, $T=1\mathrm{}$ are calculated in the plane-wave Born approximation. The predicted form factors and the associated predictions for $B\left(M1\mathrm{}\right)\mathrm{}$ and $B$ (Gamow-Teller) are compared to existing experimental values.

NUCLEAR STRUCTURE Predicted strengths of isospin-changing $M1\mathrm{}$, Gamow-Teller, and ($p, n$) transitions between $J=0^{+} \mathrm{and} 1^{+}$ states in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and form factors for ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(e, e^{\prime })$; shell-model wave functions, complete $\mathrm{sd}$-shell basis space, universal $\mathrm{sd}$-shell Hamiltonian.

An improved version of the particle-rotor model with an exact diagonalization of the pairing and the two-body recoil interactions has been applied to ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$. The difficulties related to the ad hoc Coriolis attenuation factor have disappeared and the low-spin antialigned states in ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$ are well reproduced by the model.

NUCLEAR STRUCTURE Pairing plus recoil model calculations for ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$ level energies and wave functions, Coriolis attenuation factor removed.

A complete set of the low lying $\frac{1}{2^{-}}$ and $\frac{3}{2^{-}}$ levels of ${}_{}{}^{197,199}{}_{}{}^{}\mathrm{Pt}$ was obtained from measurements of the primary $\gamma$-ray spectra following average resonance neutron capture experiments at incident neutron energies centered at 2 and 24 keV. A combination of the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Pt}$ results with those of a recent ($t, p$) experiment allows the further restriction of spin-parity assignments, including some for levels with $J\ge \frac{5}{2}$. The results are discussed in comparison with those previously obtained for ${}_{}{}^{195}{}_{}{}^{}\mathrm{Pt}$ in terms of the Nilsson model and the recently proposed multi-$j$ supersymmetry that may apply in this O(6)-like region.

NUCLEAR STRUCTURE ${}_{}{}^{196}{}_{}{}^{}\mathrm{Pt}(n, \gamma )$, ${}_{}{}^{198}{}_{}{}^{}\mathrm{Pt}(n, \gamma )$, $E_n=2, 24$ keV; measured $E_{\gamma }$, $I_{\gamma }$; ${}_{}{}^{197}{}_{}{}^{}\mathrm{Pt}$, ${}_{}{}^{199}{}_{}{}^{}\mathrm{Pt}$, deduced levels, $J$, $\pi$. Ge(Li) detectors, enriched targets, ARC spectroscopy. Comparison with predictions of multi-$j$ supersymmetry in the interacting boson fermion approximation model.