The levels of ${}_{}{}^{183}{}_{}{}^{}\mathrm{Re}$ and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Re}$ have been studied through the ($\alpha ,2n\gamma$) and ($\alpha ,4n\gamma$) reactions with a ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ target. Besides confirming and extending the levels of the ${\frac{5}{2}}^{+}\left[402\mathrm{}\uparrow \right]$ and ${\frac{9}{2}}^{-}\left[514\mathrm{}\uparrow \right]$ bands, two new members, ${\frac{21}{2}}^{-}$ and ${\frac{25}{2}}^{-}$, of the ${\frac{1}{2}}^{-}\left[541\mathrm{}\downarrow \right]$ band in ${}_{}{}^{183}{}_{}{}^{}\mathrm{Re}$ and existence and relative location of seven new members, ${\frac{5}{2}}^{-}$, ${\frac{9}{2}}^{-}$, ${\frac{13}{2}}^{-}$, ${\frac{17}{2}}^{-}$, ${\frac{21}{2}}^{-}$, ${\frac{25}{2}}^{-}$, and ${\frac{29}{2}}^{-}$, of the ${\frac{1}{2}}^{-}\left[541\mathrm{}\downarrow \right]$ band in ${}_{}{}^{181}{}_{}{}^{}\mathrm{Re}$ are established. A few new lifetimes are measured and some side feeding to the levels of the above bands is established.

NUCLEAR REACTIONS ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}(\alpha ,2n\gamma ){}_{}{}^{183}{}_{}{}^{}\mathrm{Re}$ and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}(\alpha ,4n\gamma ){}_{}{}^{181}{}_{}{}^{}\mathrm{Re}$, $E_{\alpha }=25\mathrm{}-63$ MeV; measured $\sigma (\gamma ,E_{\alpha })$, $\sigma \left(\theta \right)$, $\gamma -\gamma$ coincidence, $\gamma -t$ distributions; deduced decay schemes, $J$, $\pi$, $T_{\frac{1}{2}}$.

The ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}\mathrm{}(t,p)\mathrm{}{}_{}{}^{89}{}_{}{}^{}\mathrm{Sr}$ reaction has been studied at a bombarding energy of 20 MeV. The lowest states excited are basically of single particle character and the corresponding ($t,p$) differential cross sections contain a mixture of $L$ values. A comparison of these cross sections to distorted wave (DW) calculations yields qualitative information concerning configuration mixing in these states based both on the magnitudes as well as the shapes of the angular distributions. Analysis of the data is made partly by a comparison of DW calculations to the observed ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}\mathrm{}(t,p)\mathrm{}$ differential cross section and partly by comparing experimental angular distributions of the ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}\mathrm{}(t,p)\mathrm{}{}_{}{}^{90}{}_{}{}^{}\mathrm{Sr}$ reaction with those from ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}\mathrm{}(t,p)\mathrm{}$. The higher lying states observed in this experiment may be explained from the coupling of the $1g_{\frac{9}{2}}$ neutron hole to the multipole pairing phonons, represented by the low lying states of ${}_{}{}^{90}{}_{}{}^{}\mathrm{Sr}$.

NUCLEAR REACTIONS ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}\mathrm{}(t,p)\mathrm{}$, $E=20\mathrm{}$ MeV measured $\sigma \left(\theta \right)$, ${}_{}{}^{89}{}_{}{}^{}\mathrm{Sr}$ levels, DWBA deduced $l$, $\pi$.

The reaction ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}\mathrm{}(p,t)\mathrm{}{}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ was studied at 41.7 MeV; angular distributions were obtained over the range from 10 to 60°. The lowest $T=1,0^{+}$ state was identified at 9.386 ± 0.012 MeV by comparison with the analog reaction ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}(p,{}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^{40}{}_{}{}^{}\mathrm{K}$ (1.639 MeV). The weak population of these states is attributed to destructive interference between $d_{\frac{3}{2}}^{}{}_{}{}^2$ pickup from the two-particle component of ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ and $f_{\frac{7}{2}}^{}{}_{}{}^2$ pickup from the four-particle two-hole component of ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$. The excitation energy of these states cannot be accounted for by the $f_{\frac{7}{2}}-d_{\frac{3}{2}}$ effective interaction. Spectroscopic amplitudes for the Gerace-Green wave functions are calculated in a shell-model basis. Distorted-wave Born-approximation (DWBA) calculations for the lowest $T=0\mathrm{}$ and $T=1,3^{-}, \mathrm{and} 5^{-}$ states are in qualitative agreement with the data. The DAWA calculations for the positive-parity states show greater pickup strength to the two-particle two-hole $0^{+}$ and $2^{+}$ states than to the four-particle four-hole $0^{+}$ and $2^{+}$ states. The experimental results are the opposite: the four-particle four-hole states are populated more strongly than the two-particle two-hole states. Although there are uncertainties in the DWBA calculations, it is suggested that the inability to account for the observed two-nucleon pickup demonstrates a deficiency in the Gerace-Green model.

NUCLEAR REACTIONS ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}\mathrm{}(p,t)\mathrm{}$, $E=41.7\mathrm{}$ MeV; measured $\sigma (E_t,\theta )$. ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ deduced levels, $J$, $\pi$, $l$. Enriched target.

The height of the fission barrier and the character of the low lying single particle levels have been determined for the fission transition nucleus ${}_{}{}^{227}{}_{}{}^{}\mathrm{Ra}$ by fitting the energy variation of the previously reported fission cross section and fragment angular distributions in the neutron energy range $3.6<\mathrm{}{E}_n<4.1\mathrm{}$ MeV using a Hauser-Feshbach formalism. The best fit to the experimental data gave a fission barrier height $E_f=8.2\mathrm{}\pm 0.1$ MeV and a single particle state sequence at the barrier of $\frac{3}{2}$, ½, $\frac{5}{2}$, ½, which agrees very well with the theoretical predictions of Nix and Möller. An extension of the calculations to higher neutron energies ($4.7<\mathrm{}{E}_n<9.0\mathrm{}$) allowed deduction of $K_0^{}{}_{}{}^2$ and the transition nucleus level density as a function of excitation energy. A discontinuity in the $K_0^{}{}_{}{}^2$ values suggests a value of the pairing gap parameter ($2{\Delta }_f=2.7\mathrm{}$ MeV) that is considerably larger than the corresponding one at the equilibrium deformation ($2{\Delta }_0=1.7\mathrm{}$ MeV). The transition nucleus and residual nucleus level densities were compared with theoretical calculations and support the view that a collective rotational and vibrational enhancement of the intrinsic nuclear level density is necessary to account for the experimental data.

NUCLEAR REACTIONS, FISSION ${}_{}{}^{226}{}_{}{}^{}\mathrm{Ra}\mathrm{}(n,f)\mathrm{}$, $E=3.6\mathrm{}-9.0$ MeV; ${}_{}{}^{227}{}_{}{}^{}\mathrm{Ra}_{}^{*}{}_{}{}^{}$ deduced levels, $K$, $\pi$, $K_0^{}{}_{}{}^2$, and level density.

The results of neutron time of flight spectroscopy measurements for the separated Cd isotopes (110, 112, 114, 116) and for natural Cd, using the Nevis synchrocyclotron, are given. Transmission and self-indication measurements were made for a range of sample thicknesses for natural Cd, and for each of the above even A separated isotopes. Resonance parameters, ${\mathrm{E}}_0$ and $\mathrm{}\left(g\right)\mathrm{}{\Gamma }_n^0$ are given to ∼ 10 keV for 110, 112, 114, 116, and to 2.3 keV for 111 and 113. The ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$ level assignment is from recent published measurements at the Oak Ridge electron linear accelerator using a sample enriched in ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$. Levels in ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ are those stronger ones seen in natural Cd, but not identified as due to other isotopes. We also obtained level parameters to ∼ 10 keV for 181 levels which have no isotopic assignment. Many resonance ${\Gamma }_{\gamma }$ and $J$ values were obtained for 111 and 113, and a few ${\Gamma }_{\gamma }$ values for even $A$ isotopes, with $〈{\Gamma }_{\gamma }〉$ of each isotope being between 100 and 110 meV. The ${10}^4{S}_0$ values are 0.50 ± 0.10, 0.38 ± 0.06, 0.53 ± 0.09, 0.43 ± 0.07, 0.70 ± 0.19, and 0.20 ± 0.06 for 110, 111, 112, 113, 114, and 116, respectively. Comparison of the ${\left(g{\Gamma }_n^0\right)}^{\frac{1}{2}}$ distributions with Porter-Thomas theory for 110, 112, 114, and 111 shows that many $p$ levels are observed. An estimate of the level detection sensitivity and a Bayes's theorem analysis permit us to identify the detected $p$ levels, and to determine the $p$ strength function with a relatively small uncertainty. Few expected missing weak $s$ levels for each of these isotopes were then added to their $p$ level subtracted sets. Various statistical tests were applied, showing that the final $s$ level selection choices for 110, 112, 114 and 111 are in good agreement with the orthogonal ensemble theory. The ${10}^4{S}_1$ values for 110, 112, 114, and 111 are 2.8 ± 0.6, 2.5 ± 0.5, 3.2 ± 1.0, and 3.5 ± 0.7. The $〈D〉$ values for $s$ population are (174 ± 18) eV (110); (24.0 ± 1.5) eV (11); (137 ± 8) eV (112); (22.1 ± 3.8) eV (113); (183 ± 29) eV (114); and (264 ± 38) eV (116).

NUCLEAR REACTIONS ${}_{}{}^{110,111,112,113,114,116}{}_{}{}^{}\mathrm{Cd}\mathrm{}(n,n)\mathrm{}$, $n,\gamma$, $E=0\mathrm{}-10$ keV; measured ${\sigma }_t\mathrm{}\left(E\right)\mathrm{}$; deduced $E_0$, $g{\Gamma }_n$, ${\Gamma }_{\gamma }$, $J$, $S_0$, $〈D_0〉$, $S_1$; O.E. theory test.

Cross-bombardement experiments were carried out to produce the same compound nucleus ${}_{}{}^{158}{}_{}{}^{}\mathrm{Er}$ either in (${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ + ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ge}$) or (${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ + ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sn}$) reactions. Also the compound nucleus ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$ was formed by using ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$ targets. Evaporation residues ${}_{}{}^{152}{}_{}{}^{}\mathrm{Er}$ and ${}_{}{}^{153}{}_{}{}^{}\mathrm{Er}$ were detected, and excitation functions were constructed for $\mathrm{Kr},xn$ and $\mathrm{Ar},xn$ reactions, where x varies from 3 to 6. Some measurements were also made of $\mathrm{Ar},pxn$ and $\mathrm{Kr},pxn$ reactions leading to ${}_{}{}^{152}{}_{}{}^{}\mathrm{Ho}$. A comparison of the absolute cross sections shows that complete fusion is more severly limited in the case of Kr ions than for Ar ions, at the same values of excitation energy and of maximum orbital angular momentum. It was deduced that the critical angular momentum is lower in the case of krypton bombardments, $52\hslash$ instead of $76\hslash$ for Ar at ${\mathrm{E}}^{*}$ = 80 MeV. Also, the measured excitation functions are narrower for $\mathrm{Kr},xn$ than for $\mathrm{Ar},xn$ reactions and the Kr thresholds are shifted to higher energies by some 15 MeV, as if more energy were necessary for emitting a given number of neutrons in the $\mathrm{Kr},xn$ reactions than in the $\mathrm{Ar},xn$ reactions. Such an effect cannot be explained in terms of the deexcitation of the compound nucleus. We conclude that in the case of krypton-induced reactions on germanium, some particular aspects of the formation stage of the compound system may dissipate energy prior to attainment of full equilibrium.

NUCLEAR REACTIONS ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}$, ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ge}$, ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ge}(\mathrm{Kr},xn){}_{}{}^{152,153}{}_{}{}^{}\mathrm{Er}$; ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sn}(\mathrm{Ar},xn){}_{}{}^{152,153}{}_{}{}^{}\mathrm{Er}$. $\overline{E}=110\mathrm{}-300$ MeV, measured $\sigma \left(\overline{E}\right)$. Deduced complete fusion cross section and dynamical effects in the entrance channel (Kr + Ge).

The ($d, {}_{}{}^3{}_{}{}^{}\mathrm{He}$) reactions on ${}_{}{}^{96,98,100}{}_{}{}^{}\mathrm{Mo}$ have been used at 40.7 MeV bombarding energy to populate proton hole states in the Nb isotopes. Ten groups of levels were observed in each nucleus and most of the expected strength in the $1g_{\frac{9}{2}}$, $2p_{\frac{1}{2}}$, $2p_{\frac{3}{2}}$, and $1f_{\frac{5}{2}}$ orbits was observed. Excitation energies and $l$ values were obtained for nine new excited levels in ${}_{}{}^{99}{}_{}{}^{}\mathrm{Nb}$. The $Q$ value for the ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}(d,{}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^{99}{}_{}{}^{}\mathrm{Nb}$ reaction was measured to be -5.639 ± 0.015 MeV, giving a ${}_{}{}^{99}{}_{}{}^{}\mathrm{Nb}$ mass excess of -82 342 ± 15 keV. A hole-core coupling model is used to predict the levels of the Nb isotopes, and fair agreement with experiment is obtained.

NUCLEAR REACTIONS, NUCLEAR STRUCTURE ${}_{}{}^{96,98,100}{}_{}{}^{}\mathrm{Mo}(d,{}_{}{}^3{}_{}{}^{}\mathrm{He})$, $E=40.7\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$, ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}(d,{}_{}{}^3{}_{}{}^{}\mathrm{He})$ $Q$ value; ${}_{}{}^{95,97,99}{}_{}{}^{}\mathrm{Nb}$ levels deduced $l$, $S$, $\pi$, ${}_{}{}^{99}{}_{}{}^{}\mathrm{Nb}$ mass excess; calculated $J$, $\pi$, $S$, particle-core-coupling model, predicted $Q_{2^{+}}$ for ${}_{}{}^{96,98,100}{}_{}{}^{}\mathrm{Mo}$.

Relative yields of 35 products extending from ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ to ${}_{}{}^{76}{}_{}{}^{}\mathrm{Br}$ have been measurd for the interaction of 3.9-GeV (278-MeV/amu) ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ions with copper. For purposes of comparison, cross sections of 54 nuclides produced by the irradiation of Cu with 3.9-GeV protons are also reported. Although the over-all patterns of yields for ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ions and protons are qualitatively similar, there are significant differences. In the mass region $37\le A\le 64$, the mass yield curve for ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ions decreases more rapidly with decreasing $A$ than does the proton curve. No difference could be detected in the shapes of the charge dispersion curves. However, the data indicate a small shift ($<0.1Z$ unit) favoring neutron-deficient products near the target in the case of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ions. The mass yield curves appear to have similar shapes from $A\approx 40$ down to $A\approx 24$, but formation of the still lighter products, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ and particularly ${}_{}{}^3{}_{}{}^{}\mathrm{H}$, is favored in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ irradiation. An observed enhancement of products such as ${}_{}{}^{62}{}_{}{}^{}\mathrm{Zn}$, ${}_{}{}^{66}{}_{}{}^{}\mathrm{Ga}$, and ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ge}$ is interpreted as arising largely from secondary reactions rather than from primary processes which add charge or mass from the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ to the target nuclei. Some discussion of results from this and other experiments with high-energy protons and heavy ions with complex nuclei is presented in terms of the concepts of limiting fragmentation and factorization.

NUCLEAR REACTIONS Cu(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, spallation), $E=3.9\mathrm{}$ GeV; measured relative $\sigma \mathrm{}(A,Z)\mathrm{}$, 35 products ${}_{}{}^3{}_{}{}^{}\mathrm{H}$-${}_{}{}^{76}{}_{}{}^{}\mathrm{Br}$. $\mathrm{Cu}(p, \mathrm{spallation})$, $E=3.9\mathrm{}$ GeV; measured $\sigma \mathrm{}(A,Z)\mathrm{}$, 54 products ${}_{}{}^3{}_{}{}^{}\mathrm{H}$-${}_{}{}^{69}{}_{}{}^{}\mathrm{Ge}$. Natural targets, Ge(Li), $\beta$ counting, radiochemistry.

The first reported measurements of the $\beta$ decay, half-life, and mass of ${}_{}{}^{23}{}_{}{}^{}\mathrm{F}$ are presented. This isotope is the last of the eight $T_z=+\frac{5}{2}$ nuclei in the $2s-1d$ shell whose masses have been measured and compared to theory. ${}_{}{}^{23}{}_{}{}^{}\mathrm{F}$ was produced by the ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}{}_{}{}^{18}{}_{}{}^{}\mathrm{O}(\alpha ,p){}_{}{}^{23}{}_{}{}^{}\mathrm{F}$ reaction with 42-MeV ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ ions and a target of BeO enriched to 94% in ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$, and was transferred pneumatically to a remotely located station where delayed $\gamma$ rays and $\beta$ rays were counted with Ge(Li) and NE 102 detectors, respectively. $\gamma$-ray energies (in keV) and relative intensities for the ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$ daughter transitions are 492.50 ± 0.57 (10.8 ± 2.8), 815.14 ± 0.53 (24.8 ± 4.7), 1016.62 ± 0.40 (20.1 ± 5.5), 1701.44 ± 0.15 (100 ± 4.7), 1822.25 ± 0.21 (47.4 ± 2.6), 1919.32 ± 0.54 (19.3 ± 2.5), 2129.24 ± 0.39 (68.0 ± 11.4), 2314.70 ± 0.53 (7.7 ± 2.7), 2414.34 ± 0.41 (14.8 ± 3.4), 2516.50 ± 0.51 (2.9 ± 1.0), 2734.48 ± 0.44 (11.9 ± 1.6), 3431.28 ± 0.35 (25.4 ± 1.6), and 3830.52 ± 0.36 (6.8 ± 0.9). The strongest observed $\beta$ branch populates a previously unreported state in ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$ at 3831-keV excitation energy. The ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$ excitation energies (in keV) and relative β-branching intensities are 0 (<6250), 1016.64 ± 0.40 (<4.6), 1701.51 ± 0.15 (<3.8), 1822.33 ± 0.21 (14.4 ± 1.8), 2314.84 ± 0.53 (9.6 ± 2.0), 2516.65 ± 0.51 (4.7 ± 2.8), 3220.7 ± 0.7 (<1.2), 3431.55 ± 0.35 (21.9 ± 2.1), 3830.86 ± 0.36 (34.9 ± 5.3), 3836.9 ± 0.7 (<1.1), and 4435.99 ± 0.41 (14.5 ± 1.3). $\gamma$-ray branching ratios for several states in ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$ are presented, and the half-life of ${}_{}{}^{23}{}_{}{}^{}\mathrm{F}$ is 2.23 ± 0.14 sec. By measuring the energy spectra of $\beta$ rays coincident with each of the 1702-, 1822-, 2734-, and 3432-keV $\gamma$ rays, the mass excess of ${}_{}{}^{23}{}_{}{}^{}\mathrm{F}$ has been determined to be +3360 ± 170 keV. This value is compared with the transverse relationship as well as the extreme single-particle shell-model predictions. Reported mass measurements for the complete $T_z=+\frac{5}{2}$ $2s-1d$-shell series are compared with the transverse relationship predictions, and a very systematic $S$-shaped deviation from the predictions is observed. The $\beta$-decay matrix elements coupling ${}_{}{}^{23}{}_{}{}^{}\mathrm{F}$ and ${}_{}{}^{23}{}_{}{}^{}\mathrm{Ne}$ are consistent with $J^{\pi }={\frac{5}{2}}^{+}$ for ${}_{}{}^{23}{}_{}{}^{}\mathrm{F}$, as the extreme single-particle shell model would predict.

RADIOACTIVITY ${}_{}{}^{23}{}_{}{}^{}\mathrm{F}$: measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, $E_{\beta }$, $I_{\beta }$, $log\mathrm{ft}$, mass; deduced decay scheme; mass compared to theories.

The isomer ${}_{}{}^{207}{}_{}{}^{}\mathrm{Rn}_{}^m{}_{}{}^{}$ was produced via the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}({}_{}{}^{14}{}_{}{}^{}\mathrm{N},4n)$ reaction and also by bombardment of natural Hg targets with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ions. The isomer with a half-life of 181 ± 18 μs was found to decay by a cascade of two transitions 234 keV ($M2\mathrm{}$) and 665.1 keV ($E2\mathrm{}$) to the Rn ground state and was assigned as an $i_{\frac{13}{2}}$ shell-model state.

NUCLEAR REACTIONS ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}({}_{}{}^{14}{}_{}{}^{}\mathrm{N},4n)$, $E=70\mathrm{}-120$ MeV; nat $\mathrm{Hg}({}_{}{}^{12}{}_{}{}^{}\mathrm{C},5\mathrm{}-7n)$, $E=126\mathrm{}$ MeV. RADIOACTIVITY ${}_{}{}^{207}{}_{}{}^{}\mathrm{Rn}_{}^m{}_{}{}^{}$; measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, $\gamma K\mathrm{x}$ coin; ${}_{}{}^{207}{}_{}{}^{}\mathrm{Rn}_{}^m{}_{}{}^{}$ deduced multipolarities, levels, $J$, $\pi$.

Target foils ${}_{}{}^{245}{}_{}{}^{}\mathrm{Cm}$ or ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ prepared by electrodeposition on high-purity aluminum foils were irradiated in a Savannah River Plant production reactor operated in a high flux mode. The ${}_{}{}^{135}{}_{}{}^{}\mathrm{Xe}$ activity was measured for each foil as a function of time-after-irradiation by counting the 249.6-keV $\gamma$-ray emission with a 45-${\mathrm{cm}}^3$ Ge(Li) detector. From these measurements, the fraction of the $A=135\mathrm{}$ mass chain produced directly as ${}_{}{}^{135}{}_{}{}^{}\mathrm{Xe}$ relative to the total production of ${}_{}{}^{135}{}_{}{}^{}\mathrm{I}$ plus ${}_{}{}^{135}{}_{}{}^{}\mathrm{Xe}$ was calculated. The measured fractional independent yield of ${}_{}{}^{135}{}_{}{}^{}\mathrm{Xe}$ from ${}_{}{}^{245}{}_{}{}^{}\mathrm{Cm}$ fission is 0.17 ± 0.02, and from ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ fission is 0.36 ± 0.03. These yields are compared with those of ${}_{}{}^{135}{}_{}{}^{}\mathrm{Xe}$ from thermal-neutron-induced fission of ${}_{}{}^{233}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$,${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$, and ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$.

RADIOACTIVITY, FISSION ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}\mathrm{}(n,f)\mathrm{}$, ${}_{}{}^{245}{}_{}{}^{}\mathrm{Cm}\mathrm{}(n,f)\mathrm{}$; measured $\gamma$ activity of fission product ${}_{}{}^{135}{}_{}{}^{}\mathrm{Xe}$; deduced fractional independent fission yields. Ge(Li) detector, 2.6 keV at 1332.5 keV. No chemical separation.

The $g$ factor of the 632 keV level ($T_{\frac{1}{2}}=60\mathrm{}\pm 6$ psec) in ${}_{}{}^{77}{}_{}{}^{}\mathrm{As}$, populated in the 11.3 h ${\beta }^{-}$ decay of ${}_{}{}^{77}{}_{}{}^{}\mathrm{Ge}$, has been measured using the perturbed angular correlation technique. Large magnetic hyperfine fields present at arsenic in an iron host are used. Measurements were made using the 558-417 keV $\gamma$ cascade through the 632 keV level. From the directional correlation of this cascade and the measured mean precession angle $\omega \tau$ for the 632 keV level, the $g$ factor for this state has been calculated. The results obtained are $\omega \tau =0.148\mathrm{}\pm 0.019$ and $g=+1.01\mathrm{}\pm 0.16$. The measured value of the $g$ factor is compared with the predictions of various nuclear models applicable to nuclei in this region.

RADIOACTIVITY ${}_{}{}^{77}{}_{}{}^{}\mathrm{Ge}$, measured $\gamma \gamma \left(\theta \right)$, $\gamma \gamma (\theta ,H)$. ${}_{}{}^{77}{}_{}{}^{}\mathrm{As}$ levels, deduced $g$.

The locations of 13 energy levels have been deduced from $\gamma$-ray single and $\gamma -\gamma$ coincidence measurements on the $\mathrm{EC}-{\beta }^{+}$ decay of ${}_{}{}^{177}{}_{}{}^{}\mathrm{Ta}$ to ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}$. Four energy levels and 14 $\gamma$ rays associated with ${}_{}{}^{177}{}_{}{}^{}\mathrm{Ta}$ decay were unknown from the previous NaI(Tl) work. The $log\mathrm{ft}$ values have been assigned to ${}_{}{}^{177}{}_{}{}^{}\mathrm{Ta}$ $\mathrm{EC}-{\beta }^{+}$ decay, and multipolarities of several transitions have been determined with use of earlier conversion electron data.

RADIOACTIVITY ${}_{}{}^{177}{}_{}{}^{}\mathrm{Ta}$; Measured $E_{\gamma }$, $I_{\gamma }$, $\gamma -\gamma$ coin; deduced $log\mathrm{ft}$ ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}$; deduced levels, $I$, $\pi$. Ge(Li) detectors.

We have measured with high accuracy the $\gamma$ rays from 66-sec ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mn}$, 1.6-min ${}_{}{}^{57}{}_{}{}^{}\mathrm{Mn}$, and 2.6-h ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$. Thirty-seven $\gamma$ rays were observed from ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mn}$ decay which were incorporated into a ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$ level scheme with 17 excited states below 4.9 MeV. Present evidence favors a $3^{+}$ assignment for the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mn}$ ground state, but the $\beta$ decays to low-lying $2^{+}$ states are hindered. Additional weak $\gamma$ transitions giving rise to new $\beta$-decay modes were observed from ${}_{}{}^{57}{}_{}{}^{}\mathrm{Mn}$ and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$ decays.

RADIOACTIVITY ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mn}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Mn}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$; measured $E_{\gamma }$, $I_{\gamma }$. ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ deduced levels, $log\mathrm{ft}$, $J^{\pi }$. Enriched targets, Ge(Li) detector.

The spectrum of $\gamma$ rays in the 8- to 20-MeV range has been measured for ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ spontaneous fission using a 25.4 cm×25.4 cm NaI crystal and time-of-flight separation of $\gamma$ rays and neutrons. These data, obtained at three solid angles, are in disagreement with the recent result of Brooks and Reines that $\gamma$-ray events above 10 MeV in their experiment were due to two correlated $\gamma$ rays detected simultaneously. A statistical calculation using the Hauser-Feshbach formalism was performed for the deexcitation of the highly excited fission fragments. The computed $\gamma$-ray spectrum in the energy range 8-17 MeV has the same shape as the measured spectrum but is lower than the measurement by a factor of 3 to 4.

RADIOACTIVITY, FISSION ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$(sf); measured $\gamma$-ray spectrum, $E_{\gamma }=8\mathrm{}-20$ MeV; performed statistical calculation of high-energy $\gamma$-ray spectrum.

$\gamma$ and conversion-electron spectra of mass-separated ${}_{}{}^{241}{}_{}{}^{}\mathrm{Cm}$ (32.8 day) samples were measured at high resolution with Ge(Li) detectors and a magnetic $\beta$-ray spectrometer; 28 $\gamma$ rays and 76 conversion lines were identified. The multipolarities of most of the 28 transitions in ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ were deduced. Two-parameter $\gamma -\gamma$ coincidences confirmed a level scheme incorporating all transitions in six rotational bands. The observed half-life of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Cm}$ via the decay of the 471.8 keV $\gamma$ ray was 32.8 ± 0.2 day. The $\alpha$ branching deduced from the measurements of $L_2$ and $L_3$ electron lines of the 145.5 keV transition in ${}_{}{}^{237}{}_{}{}^{}\mathrm{Pu}$ was (1.0 ± 0.1)%. The $\alpha$ singles spectrum of ${}_{}{}^{245}{}_{}{}^{}\mathrm{Bk}$ (5 day) decay to ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ showed 12 $\alpha$ groups feeding the 3 lowest bands. On the basis of these measurements six single-particle states in ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ have been identified. The ground state of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ is known to be $\frac{5}{2}-\left[523\right]\mathrm{}$. The following Nilsson band-head assignments have been made: (keV, $K\pi \left[N{n}_z\Lambda \right]$: 205.9, $\frac{5}{2}+\left[642\right]\mathrm{}$; $\frac{3}{2}-\left[521\right]\mathrm{}$; $623.1,\frac{1}{2}+\left[400\right]\mathrm{}$; 652.1, $\frac{1}{2}-\left[530\right]\mathrm{}$; and 670.2, $\frac{3}{2}+\left[651\right]\mathrm{}$. The 266.0 keV $E1\mathrm{}$ transition $\frac{3}{2}-\left[521\right]\mathrm{}\to \frac{5}{2}+\left[642\right]\mathrm{}$) was found to have the most highly anomalous conversion coefficients yet observed, with anomaly factors of 100-200, consistent with $E1\mathrm{}$ penetration conversion parameter sets ${\lambda }_1,{\lambda }_2$ = (18.5,283) or (-19.3, -63); the exiting 205.9 keV $E1\mathrm{}$ transition ($\frac{5}{2}+\left[642\right]\mathrm{}\to \frac{5}{2}-\left[523\right]\mathrm{}$) shows normal $E1\mathrm{}$ conversion. The 471.8 keV $M1+\sim 7\% E2\mathrm{}$ transition $\frac{3}{2}-\left[521\right]\mathrm{}\to \frac{5}{2}-\left[523\right]\mathrm{}$ also shows anomalous (factor of 3) conversion, with an $M1\mathrm{}$ penetration parameter ∼5.5. There is some indication of anomalously low $K$ conversion for transitions near $K$ threshold. Observed $P_1$ conversion line intensities are about twice the theoretical $P_1$ conversion coefficient predictions. Seven $\mathrm{KLL}$- and two $\mathrm{KLM}$ - Auger electron lines were observed and the $K$-shell fluorescent yield was deduced as (96.5 ± 0.4)%.

RADIOACTIVITY ${}_{}{}^{241}{}_{}{}^{}\mathrm{Cm}$ [from ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}(\alpha ,2n)$]; measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, $X_K$, ${\omega }_K$, $E_{\mathrm{ce}}$, $I_{\mathrm{ce}}$, $e_{\mathrm{AKLL}}$, anomalous $E1\mathrm{}$ and $M1\mathrm{}$ conversions, deduced penetration parameters and retardation, deduced ${\alpha }_{P_1}$, $\gamma \gamma$-coin, $\alpha$ branching, ${}_{}{}^{245}{}_{}{}^{}\mathrm{Bk}$ [from ${}_{}{}^{244}{}_{}{}^{}\mathrm{Cm}(\alpha ,p2n)$; measured $E_{\alpha }$, $I_{\alpha }$; deduced hindrance factors. ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ deduced levels, $log\mathrm{ft}$ (EC), $\gamma$ multipolarity, $I$, $\pi$, 6 single-particle states. Mass-separated ${}_{}{}^{241}{}_{}{}^{}\mathrm{Cm}$. Toroidal $\beta$ spectrometer at 0.05% FWHM.

Angular distributions of 37 $\gamma$ rays were observed following the decays of 161-day ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}_{}^m{}_{}{}^{}$ and 6.8-day ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}_{}^g{}_{}{}^{}$ polarized at low temperatures in the ferromagnetic cubic Laves-phase compound ${\mathrm{ZrFe}}_2$. The magnetic moment of the ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}_{}^m{}_{}{}^{}$ was deduced to be $\left|\mu \right|=(2.74\mathrm{}\pm .21){\mu }_N$, in excellent agreement with the value $\mu =+2.59\mathrm{}{\mu }_N$ computed assuming the ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}_{}^m{}_{}{}^{}$ to be the three-quasiparticle state ${\frac{7}{2}}^{+}{\mathrm{}\left[404\right]\mathrm{}}_p,{\frac{9}{2}}^{+}{\mathrm{}\left[624\right]\mathrm{}}_n,{\frac{7}{2}}^{-}{\mathrm{}\left[514\right]\mathrm{}}_n$. The magnetic hyperfine fields of Lu, Ta, Sc, and Co in ${\mathrm{ZrFe}}_2$ were deduced from the corresponding $\gamma$-ray anisotropies. Decays proceeding through the 1.1-sec ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}_{}^m{}_{}{}^{}$ were observed to show characteristic relaxation times of $T_1\approx 6.7$ sec. The $\frac{E2\mathrm{}}{M1\mathrm{}}$ mixing ratios of numerous intraband transitions in ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}$ and ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}$ were deduced, and the corresponding $\frac{(g_K-g_R)}{Q_0}$ values were computed. Several interband $\frac{M2\mathrm{}}{E1\mathrm{}}$ mixing ratios were deduced and were compared with calculations based on the Nilsson model including first-order Coriolis mixing. The 0-180° asymmetries of several ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}$ transitions were observed in an effort to see if parity mixing effects might be present due to the particularly close-lying opposite parity states of ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}$; no effects were seen to the limit of 2 × ${10}^{-4\mathrm{}}$.

RADIOACTIVITY ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}_{}^m{}_{}{}^{}$, ${}_{}{}^{177}{}_{}{}^{}\mathrm{Lu}_{}^g{}_{}{}^{}$; measured $\gamma \left(\theta \right)$ from polarized nuclei; deduced magnetic moment $\mu$, hyperfine field $H$ of impurities in ${\mathrm{ZrFe}}_2$, relaxation time, $\gamma$-ray multipole mixing ratios, $\delta \left(\frac{E2\mathrm{}}{M1\mathrm{}}\right)$, $\delta \left(\frac{M2\mathrm{}}{E1\mathrm{}}\right)$, $g_K$, $g_R$, Coriolis mixing; deduced no observable parity violation.

The half-lives of ${}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{V}$ have been determined by following the decay of the isotopes for six to ten half-lives. The half-lives were obtained by a least-squares weighted fit to the data. The half-life of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Cr}$ ($T_{\frac{1}{2}}=21.56\mathrm{}\pm 0.03$) is considerably lower than previous measurements.

RADIOACTIVITY ${}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{V}$; measured $T_{\frac{1}{2}}$.

Time reversal $T$ invariance in the nuclear interaction was investigated by observing the directional correlation of the strongly hindered 501-keV $\gamma$ ray of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}$ with the subsequent 332- and 215-keV $\gamma$ rays from a source of ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}_{}^{\mathrm{m}}{}_{}{}^{}$ polarized at low temperatures. The asymmetry of the correlation was measured to be (2.8±5.1)× ${10}^{-4\mathrm{}}$, corresponding to a phase angle between the 501-keV $E3\mathrm{}$ and $M2\mathrm{}$ multipoles given by $sin\eta =0.048\mathrm{}\pm 0.087$, consistent with the assumption of $T$ invariance. Upper limits on the out-of-phase components of the $E3\mathrm{}$ and $M2\mathrm{}$ matrix elements were determined to be 3× ${10}^{-6\mathrm{}}$ and 1× ${10}^{-8\mathrm{}}$ Weisskopf units, respectively; these extremely small upper limits result from the use of a strongly hindered $\gamma$ ray. In addition, based on these results, estimates of the magnitude of the $T$-odd potential were deduced, from which we conclude that the millistrong or electromagnetic interactions are unlikely to be a source of $T$ violations.

RADIOACTIVITY ${}_{}{}^{180}{}_{}{}^{}\mathrm{Hf}_{}^m{}_{}{}^{}$; $\gamma -\gamma$ directional correlation, time-reversal test; 501- KeV $\gamma$, measured $sin\eta$, $sin\overline{\eta }$; deduced $T$-odd parts, $E3\mathrm{}$, $M2\mathrm{}$ transition matrices; estimated $T$-odd component, Hamiltonian.

Measurements of the isomeric $\gamma$-ray energy spectra from the thermal-neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ were performed with a Ge(Li) detector for times between 20 nsec and ∼1 μsec after fission. Eighty resolved $\gamma$-ray peaks with different energies and half-lives were observed; 37 of these $\gamma$-ray peaks had not been seen in previous delayed $\gamma$-ray measurements. The fission-fragment mass numbers for many of the $\gamma$ rays were determined by comparison of the $\gamma$-ray energies and half-lives with the results of previous ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ measurements. $\gamma$ rays which decay in cascade from the same isomeric state were identified on the basis of mass numbers, $\gamma$-ray half-lives, and intensities. Isomeric $\gamma$-ray spectra from the spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ were also measured in the present experiment; the analysis of a number of strong, resolved $\gamma$ rays in these data indicated that the present results are consistent with previous ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ results, within the sum of the systematic uncertainties of the two experiments. The total energy of the resolved peaks from this experiment, when integrated over all time, is 163 and 164 keV/fission for ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$, respectively. Roughly 40% of the total energy of the resolved peaks is from $\gamma$ rays in the 1100- to 1340-keV region. Isomers in ${}_{52}{}^{134}{}_{}{}^{}\mathrm{Te}_{82}^{}{}_{}{}^{}$ and ${}_{54}{}^{136}{}_{}{}^{}\mathrm{Xe}_{82}^{}{}_{}{}^{}$ contribute most of these high-energy $\gamma$ rays. In the 140- to 1340-keV energy range and 20- to 958-nsec time interval, the energy of the observed continuum of unresolved $\gamma$ rays was ∼20 and ∼24% of the total delayed $\gamma$-ray energy for ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$, respectively. The energy of the resolved $\gamma$ rays from this experiment for ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ is about twice that for the isomers from ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ with the same range of half-lives, as observed from previous results. Most of the difference between ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ and ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ or ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ is due to seven possible $\gamma$-ray cascades.

NUCLEAR REACTIONS, FISSION ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}\mathrm{}(n,f)\mathrm{}$, ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}\mathrm{}(n,f)\mathrm{}$, and ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$, measured isomeric $\gamma$-ray $E_{\gamma }$, $T_{\frac{1}{2}};20\mathrm{}-1000$ nsec; measured $E_{\gamma }$ (total), deduced $A$; Ge(Li) with unfolding; 85-4000 keV.