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New high-precision measurements of p( γ , π) and p( γ , γ) cross sections and beam asymmetries have been combined with other polarization ratios in a simultaneous analysis of both reactions. Compton scattering has provided two important new constraints on the photo-pion amplitude. The E2/M1 mixing ratio for the N → Δ transition extracted from this analysis is EMR = -3.0% ± 0.3 (stat + sys) ± 0.2 (model).

Spin asymmetries for the ${}^{16}\mathrm{O}(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},p{\ensuremath{\pi}}^{\ensuremath{-}})$ reaction are reported for incident photon energies of 293 $\ifmmode\pm\else\textpm\fi{}$ 20 MeV, proton angles ranging from 28$\ifmmode^\circ\else\textdegree\fi{}$ to 140$\ifmmode^\circ\else\textdegree\fi{}$ (lab), and pion angles of 35$\ifmmode^\circ\else\textdegree\fi{}$ to 115$\ifmmode^\circ\else\textdegree\fi{}$. The data are compared with calculations in a quasifree plane-wave impulse approximation model. This model is in good agreement with the data at small momentum transfer $q$, but does not follow the trend of the data at large $q$. Sensitivity to the $\ensuremath{\Delta}$-nucleus potential and to modification of the $\ensuremath{\Delta}$ lifetime from nuclear medium effects are explored using a simple modification of the $\ensuremath{\Delta}$ propagator in the calculations.

Coincident protons and neutrons from the reaction [rvec ]gg[ital d][r arrow][ital pn][pi][sup 0] were measured at a photon energy of 290 MeV. Cross sections and beam asymmetries were extracted for nucleon momenta above the quasifree region for the first time. The measured cross sections are compared with the results of a cascade Monte Carlo calculation.

The first measurement of exclusive photodisintegration of He-3 with polarized photons is reported. Cross sections and asymmetries for He-3(gamma over arrow pointing right, pn)p and He-3(gamma over arrow pointing right, pp)n at 235 less-than-or-equal-to E(gamma) less-than-or-equal-to 305 MeV are compared to a theoretical calculation which includes one-, two-, and three-nucleon photon absorption. Two-nucleon absorption dominates the pn data, but is suppressed in the pp data. The pp data require the inclusion of three-nucleon absorption to describe the cross section and beam asymmetry over all momenta.

The first measurement of the reaction [sup 3]He([rvec [gamma]],[ital p])[ital X] using linearly polarized photons is reported. Cross sections and beam-polarization asymmetries for [theta][sub [ital p]][sup lab]=60[degree]--100[degree] and [ital E][sub [gamma]]=195--304 MeV are compared with a microscopic calculation which includes one-, two-, and three-nucleon absorption mechanisms. One- and two-nucleon absorption alone fails to describe the data at low proton momenta. The inclusion of three-nucleon absorption significantly improves the comparison with the measured cross sections. However, some features of the asymmetry distributions are not explained.

The reaction $^{4}\mathrm{He}$ (${\mathrm{\ensuremath{\pi}}}^{+}$,pp)pn was measured at ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=500 MeV. The angular distribution of quasifree two-body absorption which was obtained agrees in detail with the free \ensuremath{\pi}d\ensuremath{\rightarrow}pp reaction and scales according to the number of T=0 pn pairs in $^{4}\mathrm{He}$. Possible evidence for pd final-state interactions is discussed. The extrapolated total cross section for four-body absorption is 2.5\ifmmode\pm\else\textpm\fi{}0.6 mb, which is substantially less than predicted from a model based on \ensuremath{\Delta}\ensuremath{\Delta} excitation.

The tantalizing problem of the “quenching” of the Coulomb sum rule observed in medium weight nuclei is investigated in light nuclei at high momentum transfer. Inclusive electron scattering cross sections for 3,4He have been measured in the quasielastic region at electron energies between 0.9 GeV and 4.3 GeV, and scattering angles of 15° and 85°. Longitudinal (RL) and transverse (RT) response functions have been extracted using a Rosenbluth separation at constant ‖ q ‖ of 1.050 (GeV/c). The ratio of the longitudinal to the transverse reduced response functions in the negative y region reaches unity. The experimental Coulomb sum rule although with large uncertainty and conversly to the case of medium weight nuclei, saturates at high momentum to the He nucleus total charge namely Z=2.

Results from three independent measurements of the {ital p}({rvec {gamma}},{pi}{sup 0}) reaction are presented for incident photon energies between 243 and 314 MeV, and for c.m. angles of 105{degree}, 122{degree}, and 150{degree}. The ratio of cross sections measured with orthogonal states of linear polarization is sensitive to the {ital E}2 excitation of the {Delta} resonace. Comparisons are made to the predictions of various models, all of which fail to reproduce these data.

Inclusive electron scattering cross sections for {sup 3,4}He have been measured in the quasielastic region at electron energies between 0.9 and 4.3 GeV, and scattering angles of 15{degree} and 85{degree}. Longitudinal ({ital R}{sub {ital L}}) and transverse ({ital R}{sub {ital T}}) response functions have been extracted using a Rosenbluth separation at constant {vert bar}{bold q}{vert bar} of 1.050 GeV/{ital c}. The ratio of the longitudinal to the transverse reduced response functions in the negative {ital y} region reaches unity.

New precision angular distribution data for the D({gamma},{ital p}){ital n} reaction are presented for incident photon energies of 191 and 222 MeV. The difference of cross sections measured with orthogonal states of linear polarization is sensitive to the short-range behavior of the tensor interaction in models of the nuclear force. Comparisons with the Bonn and Paris potentials illustrate the sensitivity.

Inclusive electron-scattering cross sections have been measured for ^(56)Fe in the quasielastic region at electron energies between 0.9 and 4.3 GeV, at scattering angles of 15° and 85°. Longitudinal and transverse response functions at a q of 1.14 GeV/c have been extracted using a Rosenbluth separation. The experimental Coulomb sum has been obtained with aid of an extrapolation. The longitudinal response function, after correction for Coulomb distortion, is lower than quasifree-scattering-model predictions at the quasielastic peak and on the high-ω side.

One of the most interesting and fundamental challenges to arise from the study of heavy-ion collisions at bombarding energies well above the Coulomb barrier is that of understanding and describing the nature and properties of the compound nucleus. Indeed, the validity of the classical conception of an equilibrated, long-lived nucleus in which all nucleons share the available energy and angular momentum must be questioned in the regime of high excitation energies ~E~ available to experimentalists today. The occurrence of resonances in many lighter heavy-ion systems has served to focus a great deal of attention on this question since it is not altogether clear whether resonances are a signature of compound nucleus formation or depend mostly upon the entrance and/or exit channels. The work presented in this paper addresses the compound nucleus versus entrance channel effect aspect of heavy-ion reactions by searching for resonances correlated in different entrance channels leading to the same compound nucleus.

We report new high-precision measurements of $p(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},\ensuremath{\gamma}),$ $p(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},{\ensuremath{\pi}}^{0})$ and $p(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},{\ensuremath{\pi}}^{+})$ cross section and beam asymmetry angular distributions for photon beam energies in the range from 213 MeV to 333 MeV. The cross sections for all three channels are locked together with a small common systematic scale uncertainty of 2%. A large overdetermination of kinematic parameters was used to achieve the first complete separation of the Compton scattering and ${\ensuremath{\pi}}^{0}$-production channels. This has also allowed all detector efficiencies for the $p(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},\ensuremath{\gamma})$ and $p(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},{\ensuremath{\pi}}^{0})$ channels to be measured directly from the data itself without resorting to simulations. The new Compton results are approximately 30% higher than previous Bonn data near the peak of the $\ensuremath{\Delta}$ resonance, resolving a long-standing unitarity puzzle. However, our $p(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},{\ensuremath{\pi}}^{0})$ and $p(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},{\ensuremath{\pi}}^{+})$ cross sections are also about 10% higher than both earlier Bonn data and recent Mainz measurements, while our $p(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},{\ensuremath{\pi}}^{+})$ cross sections are in good agreement with results from Tokyo. Our polarization asymmetry data are of the highest precision yet available and have considerable impact upon multipole analyses. These new data have been combined with other polarization ratios in a simultaneous analysis of both Compton scattering and $\ensuremath{\pi}$ production, with Compton scattering providing two new constraints on the photopion amplitude. This analysis has improved the accuracy in the $E2/M1$ mixing ratio for the $\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\Delta}$ transition, $EMR=\ensuremath{-}[3.07\ifmmode\pm\else\textpm\fi{}0.26(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.24(\mathrm{model})](%),$ and the corresponding $\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\Delta}$ transverse helicity amplitudes, ${A}_{1/2}=\ensuremath{-}[135.7\ifmmode\pm\else\textpm\fi{}1.3(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\ifmmode\pm\else\textpm\fi{}3.7(\mathrm{model})]{(10}^{\ensuremath{-}3}{\mathrm{GeV}}^{\ensuremath{-}1/2})$ and ${A}_{3/2}=\ensuremath{-}[266.9\ifmmode\pm\else\textpm\fi{}1.6(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\ifmmode\pm\else\textpm\fi{}7.8(\mathrm{model})]{(10}^{\ensuremath{-}3}{\mathrm{GeV}}^{\ensuremath{-}1/2}).$ From these we deduce an oblate spectroscopic deformation for the ${\ensuremath{\Delta}}^{+}.$ The same simultaneous analysis has been used to extract the proton dipole polarizabilities, $\overline{\ensuremath{\alpha}}\ensuremath{-}\overline{\ensuremath{\beta}}=+[10.39\ifmmode\pm\else\textpm\fi{}1.77(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}{)}_{\ensuremath{-}1.87}^{+1.02}(\mathrm{model})]{(10}^{\ensuremath{-}4}{\mathrm{fm}}^{3})$ in agreement with previous low energy measurements, and $\overline{\ensuremath{\alpha}}+\overline{\ensuremath{\beta}}=+[13.25\ifmmode\pm\else\textpm\fi{}0.86(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}{)}_{\ensuremath{-}0.58}^{+0.23}(\mathrm{model})]{(10}^{\ensuremath{-}4}{\mathrm{fm}}^{3})$ in agreement with recent evaluations of the Baldin sum rule. Our simultaneous analysis has also provided the first determination of the proton spin polarizabilities, ${\ensuremath{\gamma}}_{\ensuremath{\pi}}=\ensuremath{-}[27.23\ifmmode\pm\else\textpm\fi{}2.27(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}{)}_{\ensuremath{-}2.10}^{+2.24}(\mathrm{model})]{(10}^{\ensuremath{-}4}{\mathrm{fm}}^{4}),$ ${\ensuremath{\gamma}}_{0}=\ensuremath{-}[1.55$$\ifmmode\pm\else\textpm\fi{}0.15(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}{)}_{\ensuremath{-}0.03}^{+0.03}(\mathrm{model})]{(10}^{\ensuremath{-}4}{\mathrm{fm}}^{4}),$ ${\ensuremath{\gamma}}_{13}=+[3.94\ifmmode\pm\else\textpm\fi{}0.53(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}{)}_{\ensuremath{-}0.18}^{+0.20}(\mathrm{model})]{(10}^{\ensuremath{-}4}{\mathrm{fm}}^{4}),$ and ${\ensuremath{\gamma}}_{14}=\ensuremath{-}[2.20\ifmmode\pm\else\textpm\fi{}0.27(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}+\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}{)}_{\ensuremath{-}0.09}^{+0.05}(\mathrm{model})]{(10}^{\ensuremath{-}4}{\mathrm{fm}}^{4}).$ The extracted value of the backward spin polarizability, ${\ensuremath{\gamma}}_{\ensuremath{\pi}},$ is considerably different from other analyses and this has been instrumental in bringing the value of $\overline{\ensuremath{\alpha}}\ensuremath{-}\overline{\ensuremath{\beta}}$ extracted from high energy data into agreement with low energy experiments.

The photodisintegration of deuterium with linearly polarized light has been measured in the energy range of 110-315 MeV. The results of five independent measurements using three detector systems, two liquid target geometries, and two photon energy distribution end points are presented. These data are combined into one average data set with a systematic uncertainty of {+-}5%. The statistical precision of this combined data set, coupled with the sensitivity to the strength of the short range tensor interaction observed in the parallel-perpendicular cross section difference, makes this an attractive reaction for investigating aspects of the NN interaction. To do this reliably requires a complete, systematic description of the reaction through the {delta} region. Recent NN-N{delta} coupled-channel calculations which include fully retarded pion potentials are compared with multipole fits to the data. These calculations cannot reproduce the energy and angle dependence of the data. The character of the disagreement suggests that the remaining problems may lie with the treatment of the {delta}. (c) 1999 The American Physical Society.

The first measurement of exclusive photodisintegration of 3He with polarized photons is reported. Cross sections and asymmetries for 3He(γ,pn)p and 3He(γ,pp)n at 235≤Eγ≤305 MeV, and fixed proton emission angle θP1=100°, are compared to a theoretical calculation which includes one‐, two‐, and three‐nucleon photon absorption. Two‐nucleon absorption dominates the pn data, but is suppressed in the pp data. Both the pn and pp data require the inclusion of three‐nucleon absorption to describe the cross section and beam asymmetry over all momenta.

In constituent quark models, a tensor interaction, mixing quark spins with their relative motion, is introduced to reproduce the observed baryon spectrum. This has a consequence completely analogous to the nuclear tensor force between the n and p in deuterium. A D state component is mixed into what would otherwise be a purely S-wave object. The D-wave component breaks spherical symmetry, resulting in a non-vanishing matrix element for the nucleon and a static quadrupole moment and deformation for its first excited state, the Δ resonance, at ∽325 MeV. The magnitude and sign of this D-state component are quite sensitive to the internal structure of the proton and have been of great interest in recent years [1].

The response function of nuclei in the quasielastic region at large momentum transfer (q\ensuremath{\le}10 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$) is measured for a series of nuclei, $^{4}\mathrm{He}$, $^{12}\mathrm{C}$, $^{27}\mathrm{Al}$, $^{56}\mathrm{Fe}$, and $^{197}\mathrm{Au}$, up to large values of the Bjorken scaling variables x2.5.

Nuclear structure functions are extracted for high-energy electron scattering from nuclei at large values of the kinematic variable x and Q^2 in the range 1–4 (GeV/c)^2. At the highest Q^2, the data for x>1 begin to display a scaling indicative of local duality.

The Laser Electron Gamma Source (LEGS)[1] has recently begun operations at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory. At LEGS, laser light is Compton backscattered from the 2.5 GeV electrons circulating in the X-Ray storage ring of the NSLS. The backscattered photons have gamma ray energies, k < 320 MeV. The corresponding scattered electrons are detected in a tagging spectrometer which is incorporated into the storage ring. This tag provides a determination of the photon energy to ~ 5 MeV [2]. Since the laser light is polarized, and since the spin-flip amplitude in Compton backscattering is very small, the resulting polarization of the gamma-ray beam is very high.

Our primary research effort continues to be at the LEGS project at Brookhaven National Laboratory. The LEGS facility has made a transition in the last year from a combination of experiment and facility construction to full time experimental work. The first experiment, photodisintegration of the deuteron with polarized {gamma} rays, is completed and partially published. A second experiment, {sup 3}He({gamma},NN), has also been completed and analysis has begun. We except to begin two more experiments in the next year. Other research efforts are primarily related to CEBAF and this work is growing, since major CEBAF experimental equipment is now being constructed. We are heavily involved in the CLAS collaboration in Hall B which will build the CEBAF Large Acceptance Spectrometer. Our contributions to the CEBAF experimental program and equipment construction are described. The {sup 3}He({gamma}, NN) experiment at LEGS was the second use, in a new format, of the University of Virginia Nucleon Detector System. It is now a fully developed system. We also describe a new area of instrument development, applications of waveshifting optical fibers to novel position sensitive detectors for neutral particles.

This report discusses the following topics: general LEGS work; photodisintegration of the deuteron; progress towards other experiments; LEGS instrumentation; major LEGS software projects; NaI detector system; nucleon detector system; waveshifting fibers; EGN prototype detector for CEBAF; photon beam facility at CEBAF; delta electroproduction in nuclei; quasielastic scattering and excitation of the Delta by {sup 4}He(e,e{prime}); and quasielastic scattering at high Q{sup 2}.

Inclusive electron-scattering measurements of \ensuremath{\Delta} electroexcitation in nuclei are reported. Electrons with energies of 0.96, 1.1, 1.3, and 1.5 GeV were scattered from $^{1}\mathrm{H}$, $^{4}\mathrm{He}$, C Fe, and W at 37.5\ifmmode^\circ\else\textdegree\fi{}, corresponding to ${Q}^{2}$=0.20--0.52 (GeV/c${)}^{2}$ at the \ensuremath{\Delta} peak. The centroid of the \ensuremath{\Delta}-region cross-section peak is above that for the free nucleon and it shifts to higher invariant mass as ${Q}^{2}$ increases. The A dependence in the dip region and ratios of nuclear to nucleon integrated cross sections indicate that at these ${Q}^{2}$ values there is little specifically nuclear, e.g., quasideuteron, background contribution.

A $^{208}\mathrm{Pb}$ target was bombarded with 97.9-MeV $^{12}\mathrm{C}$ ions accelerated in the Oak Ridge isochronous cyclotron and the reaction products detected with a 60-cm long position-sensitive proportional counter placed at the focal plane of an Elbek spectrograph. Differential cross sections were measured for the $^{208}\mathrm{Pb}$($^{12}\mathrm{C}$, $^{11}\mathrm{B}$), $^{208}\mathrm{Pb}$($^{12}\mathrm{C}$, $^{13}\mathrm{C}$), and $^{208}\mathrm{Pb}$($^{12}\mathrm{C}$, $^{14}\mathrm{C}$) reactions. The single-nucleon transfer data, together with previous measurements taken for the same two reactions at 77.4 and 116.4 MeV, were analyzed using exact finite-range, full-recoil, distorted-wave Born-approximation calculations. Elastic scattering for $^{11}\mathrm{B}$ + $^{209}\mathrm{Bi}$ at 74.6 MeV and $^{13}\mathrm{C}$ + $^{207}\mathrm{Pb}$ at 86.1 MeV was also measured and optical optical potential fits obtained to provide potentials for use in the distorted-wave Born-approximation calculations. Both Woods-Saxon and folded potentials were used in fitting the elastic data. The importance of the various interaction terms in the distorted-wave Born approximation was studied. Good agreement was found between theory and experiment for the ($^{12}\mathrm{C}$, $^{13}\mathrm{C}$) reactions, and the spectroscopic factors deduced were satisfactory. The data for the ($^{12}\mathrm{C}$, $^{11}\mathrm{B}$) reactions, although also yielding satisfactory spectroscopic factors, tend to peak at smaller angles than the predicted curves. This discrepancy increases as the $Q$ value becomes more negative or the bombarding energy is reduced; that is, as the mismatch increases between the grazing angular momenta in the entrance and exit channels.NUCLEAR REACTIONS $^{208}\mathrm{Pb}$($^{12}\mathrm{C}$, $^{13}\mathrm{C}$), $^{208}\mathrm{Pb}$($^{12}\mathrm{C}$, $^{11}\mathrm{B}$), ${E}_{\mathrm{lab}}=77.4, 97.9, 116.4$ MeV; $^{208}\mathrm{Pb}$($^{12}\mathrm{C}$, $^{14}\mathrm{C}$), ${E}_{\mathrm{lab}}=97.9$ MeV; $^{207}\mathrm{Pb}$($^{13}\mathrm{C}$, $^{13}\mathrm{C}$), ${E}_{\mathrm{lab}}=86.1$ MeV; $^{209}\mathrm{Bi}$($^{11}\mathrm{B}$, $^{11}\mathrm{B}$), ${E}_{\mathrm{lab}}=74.6$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta})$; optical model and DWBA analyses; deduced spectroscopic factors.

The mass excess of 147 Tb has been determined from the Q -value measurement of the 144 Sm( 14N , 11 Be) 147 Tb reaction to be −71.00 ± 0.05 MeV. The two-proton separation energy provides little evidence for a magic proton shell closure at Z = 64.

The exit channels for elastic and alpha particles have been detected for /sup 14/N bombardment on /sup 12/C over the energy range E/sub lab/ = 45.0--60.0 MeV. Extensive statistical analyses of the data show evidence for nonstatistical structure (or ''resonances''). Some of these structures are correlated in the two exit channels, especially one prominent structure at E/sub c.m./ = 22.4 MeV. The reaction mechanism is discussed, and all the evidence is consistent with a quasimolecular resonance formed by the /sup 14/N and /sup 12/C entrance channel nuclei.

Heavy-ion inelastic scattering is described microscopically by using an effective nucleon-nucleon interaction and RPA hole-particle wave functions. The relative cross sections for different multipoles can be sensitive to the range of the interaction. The strength is determined by fitting elastic scattering. The model is used to analyze 98 MeV 12C ions exciting 208Pb. The range required is shorter than that for the bare interaction between nucleons. Collective model fits are also presented for comparison.

Spectra for the reaction products formed 14 N bombardment of 11 B have been measured at an incident energy of 50 MeV. Comparison of the ratios of production rates of 6,7 Li, 9 Be and 11 B or 12,13 C and of the measured angular distributions for the 11 B( 14 N, 9 Be) 16 O reaction with statistical model calculations indicates that part of the 9 Be yield is due to a non-statistical reaction process.

The experimental production of p, d, t, /sup 3/He, and /sup 4/He particles at 150/sup 0/ from 720-MeV ..cap alpha.. bombardment of Al, Ag, and Ta nuclei are shown to agree with Frankel's phenomenological ''quasi-two-body-scaling'' formalism. However, we show our data to also be qualitatively consistent with multiple-scattering, thermodynamic models. More theoretical work is needed, especially to understand composite-particle production.

Proton-inclusive cross sections were measured for 600 MeV proton bombardment of 27Al and 181Ta targets using the SREL synchrocyclotron. Proton energies were measured with a plastic scintillator time-of-flight system, and a 10.2 cm thick NaI detector was used for particle identification. The results of classical many-body and knock-on calculations are compared with the data.

Cross sections for the fusion of $^{28}\mathrm{C}$ have been measured at center of mass bombarding energies of 39, 43.5, 48, and 54 MeV. Velocity and energy spectra of reaction products having charge Z\ensuremath{\ge}12 and mass number A\ensuremath{\ge}24 were studied at several angles between ${\mathrm{theta}}_{\mathrm{lab}=2\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$ and 13\ifmmode^\circ\else\textdegree\fi{}. Separation of fusion from other processes was made by comparison of kinematic calculations to measured spectra. The extracted critical angular momentum (${l}_{\mathrm{cr}{}^{\mathrm{fus})}}$ of 22\ensuremath{\Elzxh} indicates the existence of an entrance-channel-imposed limit on the high energy fusion cross section. More symmetric systems forming the same compound nucleus, $^{40}\mathrm{Ca}$, have considerably larger limiting angular momenta. This result is consistent with the previous observation of a maximum angular momentum of 22\ensuremath{\Elzxh} (relative to the entrance channel) for the orbiting dinuclear complex found in studies of back-angle deeply inelastic scattering of $^{28}\mathrm{Si}$ and $^{12}\mathrm{C}$.

States in 24 Mg were populated by the 10 B( 16 O, d) and 12 C( 16 O, α) reactions. Excitation functions at 7° for many of the levels were measured for bombarding energies between 40 and 46 MeV for the 16 O + 12 C reaction, and from 44 to 46 MeV for the 16 O + 10 B reaction. The reactions appear to be predominantly due to compound nucleus formation, and general agreement was found comparing the measured cross sections with Hauser-Feshbach calculations. The experimental cross sections for the members of the K π = 0 + and 2 + rotational bands are particularly well reproduced by the calculations up through the 8 + states.

Neutron polarization angular distributions were measured for the9Be(d,n)10B and11B(d,n)12C reactions for deuteron energies of 5.47 and 5.34 MeV, respectively. Using neutron time-of-flight techniques, polarizations to eight states in10B and to six states in12C have been measured. Neutron polarization energy excitation functions for both reactions were measured for deuteron energies from 3.0 to 5.5 MeV in 0.25 MeV steps at 30° (lab). Distorted wave method calculations carried out to compare theoretical calculations against experimental results were not in good agreement with the data.

Excitation functions at 7° (lab) have been measured from E c.m. = 5.1 to 11.4 MeV in approximately 114 keV steps for 15 groups of final states in 17 O populated by the 12 C( 9 Be, α) reaction. Statistical tests have been used to locate possible non-statistical structure in the excitation functions. Possible anomalies were found near E c.m. = 6.3, 7.5, 8.9 and 9.7 MeV. Angular distributions were measured at E c.m. = 9.20, 9.71 and 10.23 MeV for the three lowest excited states in 17 O. The data have been compared with Hauser-Feshbach calculations in addition to the following reaction mechanisms: compound plus a single resonance, compound plus interfering resonances and compound plus direct reactions.

The mass excess of 51 Ca has been determined from the Q-value measurement of the 48 Ca ( 18 O , 15 O ) 51 Ca reaction to be −0.36.12 ± 0.12 MeV. The existence of three excited states below 1 MeV excitation energy probably precludes 52 Ca from being a doubly magic nucleus as has been suggested recently.

A simple explanation based primarily on the binding energies of nuclei in the entrance channel and level densities calculated with the shell model is proposed to explain the occurence of resonances in heavy-ion reactions for sd-shell nuclei.

Accurate, confirmed mass excess values have been determined for the nuclei60, 62Fe,68Ni,69Cu, and73, 75Ga by theQ-value method. The mass of74Zn requires further study. Good agreement was found between experimentally determined mass values and those from mass model predictions.

States in20Ne were populated by the10B(16O,6Li) reaction, and levels were observed up to 11 MeV in excitation energy. Cross sections were measured at 7° (lab) for bombarding energies from 44.4 to 46 MeV in 400 keV intervals. The reaction appears to be predominantly due to compound nucleus formation, and good agreement was found between the measured cross sections and Hauser-Feshbach calculations, assuming the known spin values of20Ne.

We describe a supersonic gas jet target built for studying reactions induced by heavy ions with high energy resolution. The device produces very localized high density gas jets in a near vacuum environment and is presently installed in the scattering chamber of a magnetic spectrograph at the ORNL HHIRF. With a 100 MeV 16 O beam collimated to a size of approximately 1 mm 2 at the target, image sizes of 0.42 mm have been obtained at the focal plane of the spectrograph with a solid angle of 2.4 msr and target densities of 15–30 μg/cm 2 .