Inelastic $\alpha$ scattering was studied on ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ at 70 MeV $\alpha$ energy. With an over-all resolution of 70-100 keV 40 distinct peaks are seen in energy spectra below 16 MeV excitation. The experimental angular distributions for individual peaks were analyzed in terms of the distorted wave Born approximation to extract transition strengths. About 50-70% of the quadrupole energy-weighted sum rule strength is observed up to 19 MeV excitation. Though there is a slight peaking of $l=2\mathrm{}$ strength around 16 MeV excitation it is found to be spread over a broader (∼ 10 MeV) energy range than is the case (typically 5-6 MeV) for heavier ($A>\mathrm{}40\mathrm{}$) nuclei. Up to 16 MeV the observed strength for the octupole vibrations is 10% of the energy-weighted sum rule and it is consistent with that estimated to reside around $1\hslash \omega$ excitation. Only 3% of the $l=4\mathrm{}$ energy-weighted strength is seen below 16 MeV.

NUCLEAR REACTIONS ${}_{}{}^{28}{}_{}{}^{}\mathrm{Mg}(\alpha ,{\alpha }^{\prime })$, $E_{\alpha }=70\mathrm{}$ MeV, $E_{\mathrm{excitation}}=0\mathrm{}-30$ MeV; measured $\sigma (E_{{\alpha }^{\prime }},\theta )$ deduced quadrupole, octupole, and hexadecapole strength by DWBA and compared with sum rules. Enriched target.

Distorted-wave Born approximation calculations for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(d,{}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^{11}{}_{}{}^{}\mathrm{B}(\mathrm{g}.\mathrm{s}.\mathrm{})$ reaction at 80 MeV are reported. By using "deep" potentials to generate the exit channel distorted waves, good fits to the data are possible, contrary to previously reported results. Finite range effects are found to be small, reducing the cross sections calculated in zero range approximation by 20 to 25%. It is shown that the usual local energy approximation overestimates finite range effects.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(d,{}_{}{}^3{}_{}{}^{}\mathrm{He})$, $E=80\mathrm{}$ MeV DWBA analysis, deduced $S$.

The ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(d,\alpha )$ reaction has been studied at 26 MeV to test shell model wave functions for the deformed nucleus ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$. Excitation functions were first taken to insure that at this energy the ($d,\alpha$) reaction on ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ is direct. The distorted-wave Born approximation with optical wells of matched geometry was used. With wave functions based on a Hamiltonian calculated using level energies in a restricted region of the $s-d$ shell, the data require a roughly constant ($d,\alpha$) normalization (within the error of measurement) for 8 of the 10 states studied, indicating the overall correctness of the wave functions. A calculation using a wider range of level energies is less successful. Several new spin suggestions are made and another rotational band in ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$ is tentatively identified.

NUCLEAR REACTIONS ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(d,\alpha )$, $E=17\mathrm{}-26$ MeV; measured $\sigma \mathrm{}\left(E\right)\mathrm{}$, $\sigma \left(\theta \right)$; compared with shell model predictions; enriched targets, multigap spectrometer.

Angular distributions for elastic and inelastic deuteron scattering on ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ were measured at $E_d=60, 77, \mathrm{and} 90$ MeV. The data are analyzed by coupled channels calculations and discussed in terms of the weak coupling, strong coupling, and rotational-vibrational models for ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$. The analysis supports the concepts of rotational-vibrational interaction in ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ and suggests the level observed at $E_x=5.5\mathrm{}$ MeV to be the third ${9/2}^{+}$ member of the $K=\frac{5}{2}$ ground state band.

NUCLEAR REACTIONS ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}(d,d)$, ($d,d^{\prime }$), $E=60, 77, \mathrm{and} 90$ MeV; measured $\sigma (E,\Theta )$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ deduced levels; optical model and coupled channels analysis; deduced $L$, ${\beta }_l$; weak coupling model, rotational model, rotational-vibrational model.

In recent work it was shown how a rigorous subsidiary minimum principle of the Rayleigh-Ritz type could be used as an aid in the construction of the closed-channel part of the scattering wave function, thereby making available a potentially powerful new tool in the variational approach to multiparticle scattering problems. The earlier discussion, which was restricted to scattering below the threshold for target breakup, is generalized here to the case where both two-body and three-body channels are open. The scattering problem is formally reduced to an equivalent three-body problem. Effective two-body and three-body potentials are defined explicitly (without the use of projection operators) and integral equations of the Faddeev type are derived. This analysis, which suggests a variety of cluster approximations, is used here as the basis for a decomposition of the wave function into an open-channel part, which contains the two-body and three-body outgoing scattered waves, and a decaying closed-channel part. The closed-channel part is shown to satisfy a minimum principle whose rigor can be maintained even when the target bound-state wave functions are imprecisely known. A calculational procedure which combines this minimum principle with the Kohn variational construction of the scattering amplitude is described.

NUCLEAR REACTIONS Scattering theory. Effective three-body formulation. Derivation of extremum principle for the wave function.

In this article we discuss some aspects of the fluctuation part of the cross section at a doorway resonance. We show that in the strong absorption limit an inequality is derived for ${\Gamma }^{\downarrow }$, namely, ${\Gamma }^{\downarrow }\ge (\frac{2}{N^{\frac{1}{2}}}-1) {\Gamma }^{\uparrow }$ where $N$ is the number of open channels. In the strong absorption limit no doorway resonance appears in the average cross section.

NUCLEAR REACTIONS Intermediate structure, fluctuation cross section discussed.

Differential cross sections, at proton incident energies between 23.3 and 42.4 MeV, have been measured for the following reactions: ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}(p,d){}_{}{}^{63}{}_{}{}^{}\mathrm{Zn}$, ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}(p,t){}_{}{}^{62}{}_{}{}^{}\mathrm{Zn}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}(p,\alpha ){}_{}{}^{61}{}_{}{}^{}\mathrm{Cu}$. The data are compared with distorted wave Born approximation calculations. Although good results for the ($p,d$) data are obtained, attempts to fit the experimental energy dependence of the ($p,t$) and ($p,\alpha$) reactions are less successful. The effects of two-step processes have been investigated. It is shown that the ($p,d,t$) successive single-neutron pickup can provide a satisfactory description of the energy dependence of the ($p,t$) cross sections.

NUCLEAR REACTIONS ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}(p,d)$, ($p,t$), ($p,\alpha$), $E=23.3\mathrm{}-42.4$ MeV; measured $\sigma (E_d,\theta )$, $\sigma (E_t,\theta )$, $\sigma (E_{\alpha },\theta )$; ${\theta }_{\mathrm{lab}}=12\mathrm{}°-90°$; resolution 120 keV. Reaction mechanism analysis.

The $\gamma$ ray spectrum from thermal neutron capture on ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}$ has been studied from 100 keV to 6.4 MeV. The $\gamma$ rays were studied in singles and coincidence with Ge(Li) detectors. The results obtained together with information from the ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}\mathrm{}(d,p)\mathrm{}{}_{}{}^{143}{}_{}{}^{}\mathrm{Ce}$ reaction indicate the population by neutron capture of levels in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ce}$ with energies 18.4 ± 0.5, 42.4 ± 0.6, (56.4 ± 1.0), 632.5 ± 0.5, 808.2 ± 0.3, 862.1 ± 0.3, 1154.1 ± 0.3, 1172.5 ± 0.3, 1572.4 ± 0.5, 1620.5 ± 0.4, 1628.7 ± 0.4, 1835.2 ± 0.8, 1913.4 ± 1.1, 1945.4 ± 0.6, 1993.3 ± 0.6, 2027.4 ± 0.8, 2061.5 ± 0.6, 2202.0 ± 0.6, 2215.9 ± 0.6, 2232.1 ± 0.7, 2272.7 ± 1.0, 2313.9 ± 0.8, 2488.6 ± 1.0, and 2537.3 ± 0.8 keV. The neutron separation energy of ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ce}$ was determined to be 5145.9 ± 0.5 keV, which is in poor agreement with values obtained from currently available mass tables. The ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ce}$ level scheme was found to be similar to that of other even $Z$, $N=85\mathrm{}$ nuclei with a small group of levels close to the ground state separated by 600-700 keV from the next level. Below 1600 keV it is possible to identify levels in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ce}$ excited in both the ($n,\gamma$) and ($d,p$) reactions. For those levels which have been assigned $l_n=1\mathrm{}$ in the ($d,p$) reaction, it was found that the strengths of excitation in the ($n,\gamma$) and ($d,p$) reactions are strongly correlated as in the neighboring $N=83\mathrm{}$ nuclei ${}_{}{}^{139}{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^{141}{}_{}{}^{}\mathrm{Ce}$. This result is interpreted as indicating that direct capture plays an important role in the mechanism of the ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}(n,\gamma ){}_{}{}^{143}{}_{}{}^{}\mathrm{Ce}$ reaction.

NUCLEAR REACTIONS ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}(n,\gamma )$ $E=\mathrm{thermal}$: measured $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma$-coin. ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ce}$ deduced levels, transitions, $J$, $\pi$, $Q$.

The elastic $\alpha$-particle scattering from ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ for incident energies between 18.0 and 49.5 MeV is studied in the frame of a folding model using the free $\alpha$-nucleon interaction. The energy dependence of the imaginary form factor and that of the real well depth are deduced.

NUCLEAR REACTIONS ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}(\alpha ,\alpha )$, $E=18.0\mathrm{}-49.5$ MeV; calculated $\sigma \left(\theta \right)$; deduced optical model parameters. Folding model analysis.

Angular distributions have been measured for transitions populating residual states of ${}_{}{}^{159}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{161}{}_{}{}^{}\mathrm{Dy}$ through the ($d,t$) reaction at $E_d=17\mathrm{}$ MeV. Many of these angular distributions have shapes which are well reproduced by distorted-wave Born-approximation calculations which assume orbital angular momentum transfers $l$ which are compatible with the previously assigned spin-parities of the states. But a significant number of angular distributions are anomalous; i.e., either they cannot be fitted by any reasonable distorted-wave Born-approximation calculation or they can only be fitted with a calculation which assumes an $l$ value incompatible with the previous Nilsson model assignment of the state. While the summed spectroscopic factors are in good agreement with Nilsson model expectations, the spectroscopic factors for many levels deviate significantly from Nilsson model predictions—even though Coriolis coupling has been included in the model calculation. The observation of several strongly anomalous angular distributions along with some anomalous oscillatory large-angle structure in many additional angular distributions and large discrepancies between observed and model-predicted spectroscopic factors almost certainly indicates that the assumption of a simple one-step direct reaction mechanism breaks down for these reactions.

NUCLEAR REACTIONS ${}_{}{}^{160}{}_{}{}^{}\mathrm{Gd}(d,t)$, ${}_{}{}^{162}{}_{}{}^{}\mathrm{Gy}(d,t)$, $E_d=17\mathrm{}$ MeV, measured $\sigma \left(\theta \right)$; DWBA analysis, deduced levels, $l$ values, spectroscopic factors. Enriched targets.

The ${}_{}{}^{61,62}{}_{}{}^{}\mathrm{Ni}(p,d)$ reactions were studied at 40 MeV. A very pronounced $j$-dependence effect was observed for the $l=3\mathrm{}$ transitions. Spins and parities are assigned to levels of ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ which include two ${\frac{1}{2}}^{+}$ states. Spectroscopic factors extracted from distorted-wave Born-approximation analysis are compared to shell-model predictions.

NUCLEAR REACTIONS ${}_{}{}^{61,62}{}_{}{}^{}\mathrm{Ni}(p,d)$, $E=40\mathrm{}$ MeV; measured $\sigma (E_d, \theta )$; enriched targets. Extracted spectroscopic factors. ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ deduced levels, $L$, $J$, $\pi$.

The ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$)${}_{}{}^{35}{}_{}{}^{}\mathrm{K}$ reaction at 73.7 and 75.8 MeV was employed to make the first observation of ${}_{}{}^{35}{}_{}{}^{}\mathrm{K}$ and to measure its mass. The $Q$ value for the reaction was found to be -29.693 ± 0.020 MeV and the mass excess to be -11.170 ± 0.020 MeV. Excited states of ${}_{}{}^{35}{}_{}{}^{}\mathrm{K}$ were found at 1.56 and 2.69 MeV.

NUCLEAR REACTIONS ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$), $E=75.8, 73.7$ MeV, measured $\sigma \left(8\mathrm{}°\right)$ $Q$ value.

Counter telescope measurements of reactions of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ +${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$ have been made at laboratory energies between 169 and 337 MeV, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ +${}_{}{}^{121}{}_{}{}^{}\mathrm{Sb}$ at 282 and 340 MeV, and ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ +${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$ at 494 and 604 MeV. Measurements and results include elastic scattering, evaporation residue angular distributions and cross sections, fission plus quasifission angular distributions, kinetic energy distributions, and yields versus atomic number. Evaporation residue yields are shown to be consistent with limits predicted by evaporation calculations which include fission competition. Fusion cross sections for the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ plus ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$ or ${}_{}{}^{121}{}_{}{}^{}\mathrm{Sb}$ systems are shown to be consistent with the liquid drop limit in terms of the angular momentum at which the fission barrier is estimated to go to zero. Kinetic energies of the fissionlike yields are compared with predicted values.

NUCLEAR REACTIONS ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ +${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ +${}_{}{}^{121}{}_{}{}^{}\mathrm{Sb}$, ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ +${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$, elastic scattering, evaporation residue, fission, quasifission, measured $\sigma (E,\theta )$.

The cross section for evaporation residues produced in the complete-fusion reactions of 336-MeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ with In has been measured. After correction for the heavy residues formed in transfer reactions, the evaporation-residue cross section is found to be 530 ± 150 mb, which corresponds to a "sharp-cutoff" angular momentum for evaporation residues of $(72\mathrm{}\pm 9)\hslash$. This result is discussed in terms of various theoretical models.

NUCLEAR REACTIONS evaporation residues In (${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, Tb), $E=336\mathrm{}$ MeV; measured $\sigma (E,\theta )$; $\sigma$ for evaporation residues; discussed in terms of models.

A thin ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ target was bombarded with 98 MeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ions. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ reaction products were momentum analyzed in a magnetic spectrograph, and angular distributions were measured for several states in the residual nuclei. The inelastic scattering showed nuclear-Coulomb interference effects, and the distorted-wave Born approximation was used to extract deformation parameters. The transfer reaction data were analyzed with a finite range recoil distorted-wave Born-approximation calculation. The magnitude of the deduced spectroscopic factors agreed with previous light-ion results, but the shape of the predicted angular distributions was shifted by 5° from the experimental data.

NUCLEAR REACTIONS ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$(${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$), (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$), (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$), $E=98\mathrm{}$ MeV; measured $\sigma (E;\theta )$; deduced optical-model parameters. ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, deduced deformation parameters; ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$ deduced $S$ $\theta =12\mathrm{}°-35°$. Enriched target.

The linear polarizations of $\gamma$ rays from the deexcitation of ${}_{}{}^{104}{}_{}{}^{}\mathrm{Pd}$ and ${}_{}{}^{106}{}_{}{}^{}\mathrm{Pd}$ following (heavy ion, $xn$) reactions were measured using a Compton polarimeter. Multipolarities for these $\gamma$ rays are tabulated and level schemes are given. Polarization measurements clearly show negative parity for two major quasirotational sidebands in both ${}_{}{}^{104}{}_{}{}^{}\mathrm{Pd}$ and ${}_{}{}^{106}{}_{}{}^{}\mathrm{Pd}$.

NUCLEAR REACTIONS ${}_{}{}^{94}{}_{}{}^{}\mathrm{Zr}({}_{}{}^{13}{}_{}{}^{}\mathrm{C},3\mathrm{}n)$, $E=47\mathrm{}$ MeV; ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}({}_{}{}^{13}{}_{}{}^{}\mathrm{C},3\mathrm{}n)$, $E=42\mathrm{}$ MeV. Linear polarization of ${}_{}{}^{104}{}_{}{}^{}\mathrm{Pd}$ and ${}_{}{}^{106}{}_{}{}^{}\mathrm{Pd}$ $\gamma$ rays measured.

Particle-$\gamma$ angular correlations have been measured for a number of states above 7.3 MeV in ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ using the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}({}_{}{}^7{}_{}{}^{}\mathrm{Li},t\gamma ){}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ reaction with the tritons observed at 0°. New information on the spins and parities of several states in ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ was obtained. In addition, by demonstrating that the ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ nuclei were strongly aligned, these measurements provide support for a direct $\alpha$-particle transfer mechanism for the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}({}_{}{}^7{}_{}{}^{}\mathrm{Li},t){}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ reaction. Angular correlation and lifetime measurements employing the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}(\alpha ,p\gamma ){}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ reaction have also been performed for a number of states in ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$, including several closely spaced doublets on which previous information is incomplete or inconsistent. Lifetimes were measured by the Doppler-shift attenuation method. The results are compared with recent large basis shell model calculations.

NUCLEAR REACTIONS ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}({}_{}{}^7{}_{}{}^{}\mathrm{Li},t\gamma )$, $E=12.0\mathrm{}$ MeV; ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}(\alpha ,p\gamma )$, $E=12.0, 15.0, 18.5, 19.0$ MeV; measured $t-\gamma$, $p-\gamma$ angular correlations, Doppler-shift attenuation. ${}_{}{}^{22}{}_{}{}^{}\mathrm{Ne}$ deduced levels, $\tau$, $J$, $\pi$, $B\left(\Lambda \right)$.

Absolute yields, energy spectra, and angular distributions of heavy residual nuclei ranging from Ne to Si have been measured in the reactions ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. For each system measurements have been performed at seven beam energies corresponding to the range 7 to 14 MeV c.m. The formation of the above products is shown to be consistent with a reaction which proceeds through the formation and decay of an excited and equilibrated composite system. Systematic differences between the absolute magnitudes of the fusion cross sections of the three reactions have been observed. It is shown that these differences are closely related to the expected differences in the nuclear size and surface diffuseness of the oxygen isotopes. Possible implications for astrophysical processes are briefly discussed.

NUCLEAR REACTIONS Complete fusion of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{17}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at $E=7\mathrm{}-14$ MeV c.m. Measured $\sigma (E,\theta )$ of evaporation residues. Deduced fusion barrier characteristics.

Fragment energy correlation measurements have been made for the photofission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ with 25-MeV bremsstrahlung. The correlated energies of fission fragment pairs were measured with semiconductor detectors. Distributions of kinetic energy as a function of fragment mass were deduced. The results for the isotopes ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ are compared. They are discussed in terms of fragment shell effects and also in terms of the two-mode fission hypothesis.

NUCLEAR REACTIONS Fission ${}_{}{}^{235,238}{}_{}{}^{}\mathrm{U}(\gamma ,f)$, $E_{\gamma max}=25\mathrm{}$ MeV; measured fragment energies $E_1$, $E_2$; deduced $N(\mu ,E_K)$.

Delayed-neutron emission from mass separated heavy fission products has been studied using a sensitive neutron counter. Twelve new delayed-neutron precursors have been found, namely ${}_{}{}^{122}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{123}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{127}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{128}{}_{}{}^{}\mathrm{Cd}$ (or ${}_{}{}^{128}{}_{}{}^{}\mathrm{In}_{}^m{}_{}{}^{}$), ${}_{}{}^{128}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{129}{}_{}{}^{}\mathrm{In}$ (two isomers), ${}_{}{}^{130}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{131}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{132}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{133}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{136}{}_{}{}^{}\mathrm{Sb}$. The half-life determination for 11 other precursors has been improved.

RADIOACTIVITY ${}_{}{}^{122,123}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{127-132}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{128}{}_{}{}^{}\mathrm{Cd}$, ${}_{}{}^{133,134}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{134-136}{}_{}{}^{}\mathrm{Sb}$, ${}_{}{}^{136}{}_{}{}^{}\mathrm{Te}$, ${}_{}{}^{137-141}{}_{}{}^{}\mathrm{I}$, ${}_{}{}^{141-146}{}_{}{}^{}\mathrm{Cs}$, measured delayed neutrons; deduced half-lives.