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A number of serious problems has continued to plague the study of the 16O+28Si, 12C+24Mg and 12C+12C systems for the last 40 years. The explanation of anomalous large angle scattering data; the reproduction of the oscillatory structure near the Coulomb barrier; the out-of-phase problem between theoretical predictions and experimental data; the consistent description of angular distributions together with resonance and excitation functions data are just some of these problems. These are long standing problems that have persisted over the years and do represent a challenge calling for a consistent framework to resolve these difficulties within a unified approach. Traditional frameworks have failed to describe these phenomena within a single model and have so far only offered different approaches where these difficulties are investigated separately from one another. The present work offers a plausible framework where all these difficulties are answered. Not only it improves the simultaneous fits to the data of these diverse observables, achieving this within a unified approach for a number of nuclear systems over wide energy ranges, but it departs for its coupling potential from the standard formulation. This new feature could provide new insight in the dynamics of these reactions. It also leads to new predictions especially concerning resonance phenomena in these systems which could form the basis for some new experimental investigation.

A multi-channel data acquisition system has been commissioned for the Charissa “MEGHA” detector array. It is designed to read multiparameter events where there are many potential channels (320) but where only a fraction of these are active in any typical event. Custom-built pre- and main amplifiers process the amplitude (energy) signal from each detector and the system records both amplitude and time of arrival for each signal within an event. The signal amplitude is converted to time using the standard Wilkinson technique and then combined with its time of arrival into a single time trace. These traces are converted by multi-hit TDCs, which only convert the active channels and thus reduce the processing load. Additional custom-built CAMAC modules organise the TDC output into a suitable form for storage and transmission to a network of processor terminals over standard ethernet. This paper presents a description of the data acquisition system from preamplifier through to final storage in a VME-based system and subsequent distribution to a network of Sun terminals over ethernet. The system performance is illustrated with results from heavy-ion elastic scattering recorded with position sensitive strip detectors.

An excitation function for the {sup 12}C({sup 20}Ne,{sup 12}C[0{sub 2}{sup +}]){sup 20}Ne reaction was measured over the energy range E{sub c.m.}=22.5{endash}31.9 MeV. An enhancement in the cross section was observed between E{sub c.m.}=24.5 and 26.5 MeV in both the {sup 12}C(0{sub 2}{sup +})+{sup 20}Ne(g.s.) and {sup 12}C(0{sub 2}{sup +})+{sup 20}Ne(2{sup +}) exit channels. Oscillatory angular distributions were observed at E{sub c.m.}=25.24, 26.56, 28.50, and 30.44 MeV and the range of dominant angular momenta involved at these energies was found to be centered on 14{h_bar},15{h_bar},16{h_bar}, and 17{h_bar}, respectively. Excitation functions were also measured for the {sup 12}C({sup 20}Ne,{sup 12}C[3{sup {minus}}]){sup 20}Ne{sup {asterisk}} reaction. For the {sup 12}C({sup 20}Ne,{sup 12}C[0{sub 2}{sup +}]){sup 20}Ne reaction the data were well described by the results of coupled channel calculations. {copyright} {ital 1999} {ital The American Physical Society}

A compact and highly segmented detector array consisting of 44 gas–silicon–caesium iodide, position sensitive, particle identification detector telescopes and up to 10 position-sensitive, silicon strip detectors has been constructed for the study of light-ion–heavy-ion reactions including cluster break–up in the energy range 5–15 MeV/nucleon. The detectors are housed in a purpose built vacuum chamber. The telescopes are placed in fixed positions, covering the forward hemisphere from 3 to 30° in the laboratory with the target placed at 535 mm from the front of the telescopes or 6–52° with the target placed at 215 mm. The strip detectors are placed in any of 30 fixed positions in the forward hemisphere. For 85 MeV 12 C ions the telescope energy resolution (gas plus silicon) is 345 keV with an angular resolution of 0.03°. Using the gas–silicon section ions with Z up to 21 can be identified. For ions that pass through the silicon isotopic identification is achieved using the silicon–CsI combination. The strip detector energy resolution is 200 keV, with an angular resolution of 0.1°.

We report on new experimental data which reveal high spin resonances in 12 C+ 12 C scattering. We have measured excitation functions for the 12 C [ 12 C, 12 C(3 1 − ) + 12 C(3 1 − )] reaction over the centre of mass energy range E c.m. =31 to 45 MeV. Resonances have been observed at E c.m. =32.5, 37.5 and 43 MeV. Detailed angular correlation measurements have been performed at the energy corresponding to the peak of each resonance. From an analysis of the angular correlations we suggest a dominant angular momentum of J =22 at the highest energy. We interpret the results in terms of an α cluster model of superdeformed states in 24 Mg.

The reaction has been studied to investigate a possible overlap with the scattering resonances observed in the and channels. Evidence for the break-up of was observed, but the yield was too low to be able to associate it with specific resonances.

We present a technique by which to calibrate the energy and position of particles striking a position-sensitive strip detector using a resistive charge division read out where the precise polar angle of the detector in the scattering chamber and the relative gains in various channels are unknown. The method is illustrated for a 16-strip detector using low-energy elastic scattering of ions from different targets.

A study has been made of the 12C(16O,12C12C) α reaction between the centre of mass energies of 28.3 to 36.8 MeV. A number of resonances in 28Si have been observed for final channels leading to the unbound 10.35, 11.09 and 14.82 MeV states in 16O. At two energies associated with previously observed resonances, the angular correlations of the exit channel particles have been analysed to measure the dominant angular momentum of the 28Si compound nucleus. Additional data were acquired at two off-resonance energies for comparison. Using an essentially model independent analysis, the values obtained were all in the region of 19–21 h , and are comparable with the grazing angular momentum in the entrance channel. The results are relevant to recent theoretical predictions of planar α-cluster structures in 28Si and are discussed in the context of the model predictions.

The CO and C2 form factors are calculated for a number of light nuclei using the Bloch-Brink α-cluster model. In all cases we construct states of good angular momentum. By comparing the theoretical and experimental results it is found that the Bloch-Brink α-cluster model wave functions are reasonably accurate for most of the configurations considered. In addition, the intra-band B (E2) values of the ground-state bands of 24 Mg and 28 Si have been computed and are in reasonable agreement with the data. Finally, B (E2) values are also calculated for a few highly deformed molecular configurations in an attempt to see whether it is feasible to observe intra-band γ-rays. However, the calculations show that the branching ratios are very small.

We present angular correlations in ``Basel'' coordinates for \ensuremath{\alpha}-particle decay in measurements of $^{12}[^{12}$C${,}^{12}$C(${3}_{1}^{\mathrm{\ensuremath{-}}}$)${\ensuremath{\rightarrow}}^{8}$Be(${0}_{1}^{+}$)+ \ensuremath{\alpha}${]}^{12}$${\mathrm{C}}^{\mathrm{*}}$ scattering at ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.}$=32.5 MeV. A semiclassical model of the angular correlation function has been used to describe the observed angular correlations in the various exit channels. We demonstrate that the semiclassical result can be used even in the case where there are two nonzero spins in the exit channel if the decay products from both ejectiles are detected. We apply this new method to the mutual sequential breakup reaction $^{12}[^{12}$C${,}^{12}$C(${3}_{1}^{\mathrm{\ensuremath{-}}}$)${\ensuremath{\rightarrow}}^{8}$Be(${0}_{1}^{+}$)+\ensuremath{\alpha}${]}^{12}$C(${3}_{1}^{\mathrm{\ensuremath{-}}}$) ${\ensuremath{\rightarrow}}^{8}$Be(${0}_{1}^{+}$)+\ensuremath{\alpha}. We deduce that the scattering occurs dominantly to a final state with fully aligned spins and orbital angular momentum ${\mathit{L}}^{\ensuremath{'}}$=12 or 14. \textcopyright{} 1996 The American Physical Society.

A study of the $^{12}\mathrm{C}$${(}^{24}$Mg${,}^{16}$O $^{16}\mathrm{O}$${)}^{4}$He reaction has revealed $^{16}\mathrm{O}$ + $^{16}\mathrm{O}$ breakup from states in $^{32}\mathrm{S}$ in the excitation region ranging from 32 to 38 MeV. The spins of the states near 33, 35, and 38 MeV of excitation, obtained from angular correlations, are measured to be (${10}^{+}$ or ${12}^{+}$), (${12}^{+}$ or ${14}^{+}$), and (${14}^{+}$ or ${16}^{+}$), respectively. These may be interpreted as arising from a highly deformed band in $^{32}\mathrm{S}$. \textcopyright{} 1996 The American Physical Society.

Recently, resonances have been observed in the reactions and at MeV. Previously resonances in the reaction have been reported by Fulton et al. Here we present a new model of these resonances. We relate this model to the classical theory of both the asymmetric rotor and the symmetric top. We believe that detailed spin measurements from these data will provide evidence for the 3-fold symmetry of .

We present calculations for {sup 8}Be-{sup 8}Be cluster states in {sup 16}O based on our recent schematic coupled-channels model. We justify some of the approximations made in the schematic model in this paper. The present calculations broadly support our assumptions about the states in {sup 16}O which formed the basis of our previous calculations in {sup 24}Mg. {copyright} {ital 1996 The American Physical Society.}

A study of the 12 C( 24 Mg, 12 C 12 C) 12 C reaction has revealed discrete states at excitation energies between 20 and 30 MeV in 24 Mg. Angular correlation analyses of some of the lower energy states confirms the report by earlier authors of monotonically increasing spin values consistent with a rotational sequence. Comparison with breakup observed in the 12 C( 20 Ne, 12 C 12 C) 8 Be reaction suggests that the same states in 24 Mg are populated, while the difference in laboratory cross sections in the two reactions is interpreted as evidence for the association of the breakup states with a prolate hyper-deformed configuration appearing in theoretical calculations for 24 Mg.

The reaction {sup 12}C({sup 16}O,7{alpha}) has been studied over the center-of-mass energy range from 37.7 MeV to 51.4 MeV, in a search for evidence for a 7-{alpha} chain state in {sup 28}Si. The yields of the {sup 12}C(0{sub 2}{sup +})-{sup 12}C(0{sub 2}{sup +})-{alpha} and {sup 12}C(0{sub 2}{sup +})-{sup 8}Be-{sup 8}Be final states agree broadly with previous measurements but contain no structure, indicating that a {sup 28}Si chain state is probably not being observed. The yields for the inelastic scattering reaction {sup 12}C+{sup 16}O decaying to other excited states in {sup 12}C and {sup 16}O have also been studied. They also contain no gross structure.

The population of excited states in {sup 24}Mg and {sup 28}Si has been investigated through the reactions {sup 12}C({sup 16}O,{sup 12}C{sup 12}C){alpha} and {sup 16}O({sup 16}O,{sup 12}C{sup 16}O){alpha}, at beam energies of 80.5 and 99 MeV. The heavy-ion fragments from the breakup of the {sup 24}Mg and {sup 28}Si nuclei were detected in coincidence, permitting a study of both the reaction kinematics and the spins of the fissioning states. These measurements indicate a series of states in {sup 24}Mg between 25 and 32 MeV with spins ranging from {ital J}=10 to 14 {h_bar}. Evidence was also found for the breakup of {sup 28}Si into {sup 12}C + {sup 16}O from states between 27 and 29 MeV.

The breakup of {sup 23}Na nuclei into {sup 11}B+{sup 12}C and of {sup 24}Mg nuclei into {sup 12}C+{sup 12}C has been studied using the reactions {sup 12}C({sup 23}Na,{sup 11}B{sup 12}C){sup 12}C and {sup 12}C({sup 23}Na,{sup 12}C{sup 12}C){sup 11}B. Clear evidence was found for the breakup of the {sup 23}Na and {sup 24}Mg nuclei into the ground states of both fragments. The yieldrotect from the {sup 12}C({sup 23}Na,{sup 11}B{sub g.s.}{sup 12}C{sub g.s.}){sup 12}C{sub g.s.} reaction was concentrated in the region of excitationrotect energy in {sup 23}Na between 24 and 28 MeV and fragmented among a number of states. Therotect {sup 12}C({sup 23}Na,{sup 12}C{sub g.s.} {sup 12}C{sub g.s.)}{sup 11}B{sub g.s.} reaction was found to proceed chiefly via broad states at 22.1 and 23.9 MeV in {sup 24}Mg.

The $^{12}\mathrm{C}$${(}^{16}$O,4\ensuremath{\alpha}${)}^{12}$C reaction has been studied at a beam energy of 99 MeV. The data indicate the existence of sequential decays in the form $^{16}\mathrm{O}^{\mathrm{*}}$\ensuremath{\rightarrow}4\ensuremath{\alpha} in the exit channel. The excitation energy of the $^{16}\mathrm{O}$ nucleus and the nature of the partition process leading to the 4\ensuremath{\alpha} final state, has been reconstructed from the kinematics of the \ensuremath{\alpha} particles. States have been observed at excitation energies of 17.1, 17.5, 18.0, 18.7, 19.3, and 21.4 MeV which decay into $^{8}\mathrm{Be}$${+}^{8}$Be, $^{12}\mathrm{C}$(7.65 MeV, ${0}_{2}^{+}$)+\ensuremath{\alpha} and $^{12}\mathrm{C}$(9.64 MeV, ${3}^{\mathrm{\ensuremath{-}}}$)+\ensuremath{\alpha}. Relative partial decay widths for these three channels have been measured. Angular correlation measurements have been used to deduce the spins of several of the observed states, and indicate spins in the range 2 to 6\ensuremath{\Elzxh}.

A high resoution measurement of the $^{12}\mathrm{C}$${(}^{24}$Mg${,}^{12}$${\mathrm{C}}^{12}$C${)}^{12}$C reaction shows that the $^{24}\mathrm{Mg}$ breakup states have widths in the region of 100 to 250 keV. The energies, widths, and spins of these states are seen to be consistent with those of the $^{12}\mathrm{C}$ ${+}^{12}$C quasimolecular resonances which occur in the same region of excitation in the $^{24}\mathrm{Mg}$ nucleus.

A hybrid detector system has been constructed consisting of a gas filled ionization chamber and a large area silicon semiconductor strip detector within the same gas volume. The construction and operation of these detectors is described, together with a brief description of the electronics and data acquisition system used in cluster breakup studies. The techniques for software correction and gain matching of the detector energy signals are described and results are presented for the resolutions in energy, position and time. In a typical application, elements up to Ca are easily resolved and the positions of individual ions are measured with a resolution of

Data on the yield of the symmetric breakup of 24 Mg as a function of beam energy are presented and compared with detailed calculations of the energy dependence. The 24 Mg states seen in symmetric breakup agree with previously observed breakup states having spin and parities J π = 4 + ,(6 + ),8 + . The data allow the variations of yield for individual states to be judged, as the beam energy is varied. The variation in the yield of the 4 + states is compared in detail with calculations assuming several possible compound nuclear or direct reaction mechanisms. It is concluded that a massive ( 12 C) transfer or a simple statistical compound process are unlikely mechanisms, but that each of several other mechanisms is consistent with the data.

We review the experimental evidence for alpha chain states in 4N-nuclei. Bloch-Brink cranked cluster model calculations suggest that such states should exist in all light A=4N nuclei. Recently a strong resonance has been observed in the12C(12C,12C(O 2 + ))12C(O 2 + ) reaction at 33 MeV which has been taken as evidence of a 6-α chain state in24Mg. The angular distributions show strong peaks at 90° due to the simultaneous excitation of several nearly degenerate resonances with a range of L-values. We review our analysis of these data and present the results of calculations for the widths of resonances in hyperdeformed nuclei. We demonstrate that such resonances may have relatively narrow widths despite their high excitation energies. We surmise that the 33 MeV resonance in12C+12C scattering has a chain state structure.

We have investigated 12 C 12 C resonances via the reaction 12 C( 12 C,αα) 16 O. The reaction products were detected in coincidence at angular separations around 180° in the centre of mass. The resulting α-α angular correlations are sensitive to the spins of the excited resonances. The reaction was studied over the centre-of-mass energy region 19–32 MeV. The excitation functions reveal the presence of a number of intermediate-structure resonances. Many 12 + and 14 + resonances have been identified while there is evidence for 16 + strength at the highest energies. In addition a broad resonance is observed at E c.m. ∼ 25 MeV for the reactions which proceed via the 18.54 MeV 8 + state in 20 Ne to the 6.92 MeV 2 + (or 7.12 MeV 1 − ) state in 16 O.

We address the problem of calculating the particle decay widths from hyper-deformed nuclei. To simplify the calculation we treat the deformed nucleus as a prolate spheroid, and the particle-nucleus interaction as sharp-edged. This enables us to describe the deformed nuclear shape as an equipotential surface in a prolate spheroidal coordinate system. We model the particle-nucleus interaction by means of a spheroidal “square well” potential. Next we make the adiabatic approximation. This enables us to consider the deformed nucleus as being fixed in space . We then solve a system of coupled Schrodinger equations which describe the scattering of the particle from the deformed nucleus. These partial differential equations are separable in our chosen coordinate system. We generate prolate spheroidal wave functions to describe the particle both inside and outside the nuclear volume using a matrix diagonalization technique. The scattering problem is then solved by matching appropriate linear combinations of internal and external wave functions, and their first derivatives, at the nuclear boundary and searching for resonances as the Q -value for particle emission is varied. Using this formalism we calculate the alpha-decay widths of the recently discovered α-chain state in 24 Mg and of the proposed 16 O+ 16 O+ 16 O configuration in 48 Cr.

We demonstrate that there is a link between the underlying geometrical structure in the Bloch-Brink α-cluster model and shell structure in the axially-symmetric deformed Harmonic oscillator model. Indeed all the axially-symmetric Harmonic oscillator configurations can be related to structures formed from triangular layers of α-clusters whose centres lie on an fcc lattice. In particular all Harmonic oscillator closed-shell nuclei can be related to tetrahedral arrangements of α-cluster centers, generalizing the result known for 16O for many years. These results suggest that the octupole degree of freedom which can be associated with triangular and tetrahedral α-cluster structures could be important in such nuclei.

The α-transfer reaction 12C(16O, 20Ne∗)8Be has been studied at Elab = 150 MeV. The 16Oα angular correlations from the decay of 20Ne∗ have been measured and analysed with a strong absorption model to make spin assignments for many high-spin states at high excitation in 20Ne.

We investigate alpha-cluster geometries and collectivity in the Bloch-Brink alpha-cluster model. We find in many cases that the geometrical arrangements of the alpha-clusters can be derived from relaxed atomic and metallic ''cluster'' structures. The alpha-cluster model has a large number of collective degrees of freedom related to this geometrical structure. The most important are quadrupole and octupole deformations and we explain how these arise naturally in the model. Three other collective degrees of freedom are those associated with rotations in the three dimensional internal space defined by Buck et al. and Morinigo. Such rotations enable us to discuss mixing between different alpha-cluster configurations in a compact and elegant way. We speculate on the relevance of mixing to the excitation of the 6 alpha-chain state in Mg-24.

Resonances in C-12+C-12 and Mg-24+Mg-24 scattering have been associated with hyperdeformed configurations in the harmonic oscillator shell model and the alpha-cluster model. Resonances in Si-28+Si-28 scattering do net seem to fit into this picture so well. We present alpha-duster model calculations for superdeformed and hyperdeformed states in Ni-56. One configuration identified in our calculations corresponds to a 2:1 harmonic oscillator configuration. The others are more complex; however, none gives a totally satisfactory explanation of the Si-28+Si-28 resonances.

A study has been made of the 12C(20Ne, 12C12C)8Be reaction. The reaction is found to proceed via sequential breakup of states in 24Mg probably excited by alpha transfer onto the 20Ne projectile. The breakup occurs from a series of discrete narrow states at high excitation in 24Mg which appear to correlate with those previously observed in the 12C(24Mg,12C12C)12C reaction.

The predicted systematics of alpha chain states (one-dimensional alpha-cluster configurations) and two-dimensional alpha-cluster configurations calculated using the Bloch-Brink (BB) alpha-cluster model have recently been presented. Here we present systematics for other alpha-cluster states which arise from three-dimensional configurations predicted by the BB model. Many of the three-dimensional alpha-cluster configurations can be classed into families which are found to extend over a wide range of nuclei. We consider mostly sd-shell nuclei but present a few results for 44 Ti as well.

The recent experimental discovery of a shape eigenstate in 24 Mg has inspired calculations for one- and two-dimensional alpha-cluster configurations in a wide range of light nuclei. We review the alpha-cluster and heavy-ion resonance data available for A=4N nuclei from 12 C through 28 Si which indicate likely experimental candidates corresponding to some of these new theoretical predictions. In particular we assign the oblate structure in 24Mg to the resonances in [Formula: see text] first observed by Fulton et al. We also review the spin systematics of these data.

Some experimental techniques used in the measurement and analysis of inverse kinematic reactions are described and applied to a kinematically complete

Recently a six-alpha chain state has been discovered in 24 Mg. The Bloch-Brink cranked cluster model shows that linear chains of alpha particles are associated with stable minima in the potential-energy surface for all 4 N -nuclei. Experimental candidates in 8 Be, 12 C and 16 O have already been identified. Using a Brink-Boeker effective interaction, and allowing free variation of all parameters, we calculate the geometric arrangements and energies of the lowest alpha-chain states. These configurations are then cranked to predict the maximum angular momenta and the excitation energies that they can sustain. We conclude that states similar to that in 24 Mg should also be accessible to experimental investigation in other nuclei.

The pure harmonic oscillator model predicts a family of axially symmetric hyperdeformed states with 3:1 major to minor axis ratios. Two members of this family have previously been identified in 12C and 24Mg within the Bloch-Brink alpha-cluster model. Here we present cranked cluster model calculations for similar hyperdeformed states in 36Ar and 48Cr. We suggest that the configuration in 48Cr is associated with resonances observed in 24Mg+24Mg scattering, while that in 36Ar may be involved in the excitation of the 12C+12C barrier resonances reported recently in the 12C(24Mg, 12C, 12C)12C reaction and also in the excitation of those resonances previously observed in the 20Ne+16O reaction.

In several recent measurements the symmetric fission of 24 Mg has been reported. In this paper the results of a search for similar processes in 28 Si and 32 S are presented. In contrast to the results for 24 Mg, no evidence is seen for the fission of 28 Si to 16 O+ 12 C or 32 S to 16 O+ 16 O following inelastic excitation. However, these processes are observed to occur following pickup onto 24 Mg. The results are consistent with a simple model of the fission process developed by Harvey and suggest the existence of large scale cluster structure in all three nuclei.

A new high resolution measurement of the 12 C( 24 Mg, 12 C 12 C) 12 C breakup reaction has been performed. Sequential breakup is observed from specific states in 24 Mg at excitation energies ranging from 20 to 26 MeV. Angular correlation measurements indicate that states with spins ranging from J =4 to 8 are populated. These states are consistent with superdeformed shape isomeric bands predicted by cranked cluster model and Nilsson-Strutinsky calculations.

The decay of $^{24}\mathrm{Mg}$ at high excitation energies has been investigated by the interaction of a $^{16}\mathrm{O}$ beam with $^{24}\mathrm{Mg}$ and $^{12}\mathrm{C}$ targets. Coincident heavy-ion--heavy-ion detection allowed for the study of the $^{12}\mathrm{\ensuremath{-}}^{12}$C and $^{16}\mathrm{\ensuremath{-}}^{8}$Be decay modes of $^{24}\mathrm{Mg}$. No evidence for these processes was found in the interaction of the beam with the $^{24}\mathrm{Mg}$ target. The $^{12}\mathrm{\ensuremath{-}}^{12}$C relative energy spectra measured via the $^{16}\mathrm{O}$${+}^{12}$C reaction provide indication for the excitation of a few selected $^{24}\mathrm{Mg}$ states around 30 MeV. Spins as high as 12\ensuremath{\Elzxh}, deduced from the angular correlations, are consistent with a quasimolecular nature of these states.

A search has been performed for large cluster breakup from 40Ca following inelastic scattering. No evidence is seen for breakup to the 12C+28Si, 16O+24Mg or 20Ne+20Ne channels.

The population of 12C-12C molecular resonances in the 16O + 12C interaction has been studied in a kinematically complete experiment at 85 MeV. It was observed that the 12C-12C-α final state is mostly due to projectile excitation followed by α emission. Nevertheless in the region of higher 12C-α relative energy evidence is found for excitation of high-lying 24Mg states, decaying into the 12C-12C system.

We report the operation and performance of a compact, high-efficiency 8Be detector designed for use in breakup reaction studies. It offers a number of advantages over previous detectors in allowing accurate kinematical identification of 8Be excited states and scattering angle as well as allowing large solid angle coverage.

An analysis of the $^{12}\mathrm{C}$($^{12}\mathrm{C}$,$3\ensuremath{\alpha}$)$^{12}\mathrm{C}$ reaction was made at beam energies between 82 and 106 MeV. Decays to both the ground state and the excited states of $^{8}\mathrm{Be}$ were isolated, allowing states of different characters to be identified. In particular, evidence was found for a previously observed state at 11.16 MeV. An analysis of the angular distributions of the unnatural parity states at 11.83 and 13.35 MeV, previously assigned ${J}^{\ensuremath{\pi}}={2}^{\ensuremath{-}}$, calls into question the validity of these assignments, suggesting that at least one of the states may correspond to ${J}^{\ensuremath{\pi}}={4}^{\ensuremath{-}}$. Evidence is also found for ${1}^{\ensuremath{-}}$ and ${3}^{\ensuremath{-}}$ strengths associated with broad states between 11 and 14 MeV.

The {sup 12}C({sup 12}C,{sup 8}Be+{sup 12}C(0{sub 2}{sup +})){sup 4}He reaction has been studied with beam energies of 82-120 MeV to search for excited states in {sup 20}Ne that decay into {sup 8}Be+{sup 12}C(0{sub 2}{sup +}). The detection of five of the six final-state {alpha} particles in an array of eight, sixteen-element, strip detectors permitted the full reconstruction of the reaction kinematics. Two {sup 20}Ne resonances at 35.2 and 36.5 MeV are observed, particularly at beam energies less than 93 MeV. An analysis of the angular correlations associated with the observed resonances indicates that an angular momentum of 10 ({Dirac_h}/2{pi}) is important in this region, and thus it is possible that at least one of the resonances possesses J{sup {pi}}=10{sup +}.

The Bloch-Brink microscopic {alpha}-cluster model is used to investigate the structure of the positive and negative parity yrast bands of {sup 44}Ti. Unlike the resonating group method or the local potential model, we approximate the wave function of {sup 44}Ti by an intrinsic configuration which is obtained from a variational principle. States with good angular momenta are constructed using angular momentum projection techniques. The wave function is completely antisymmetrized and the center of mass motion is treated properly. The calculated {ital E}2 transition strengths reproduce experiment very well, but the energy spectra are in a poor agreement with the data. {copyright} {ital 1996 The American Physical Society.}

The $^{12}\mathrm{C}(^{12}\mathrm{C},^{8}\mathrm{Be}+^{8}\mathrm{Be})^{8}\mathrm{Be}$ reaction has been studied with 18 beam energies from $82\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}120\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$. The detection of four of the six final-state $\ensuremath{\alpha}$-particles in an array of eight 16-element strip detectors permitted the full reconstruction of the reaction kinematics. $^{16}\mathrm{O}$ excitation energy spectra spanning $19--40\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ were measured, which provided evidence for $^{16}\mathrm{O}$ excited states up to $35.1\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$. Angular correlation analysis indicates the dominant spins are 6 and $8\phantom{\rule{0.3em}{0ex}}\ensuremath{\hbar}$, possibly extending to $10\phantom{\rule{0.3em}{0ex}}\ensuremath{\hbar}$ at the highest excitation energies. The resulting energy-spin systematics are compared with the predictions of the $\ensuremath{\alpha}$ cluster model and cranked Nilsson-Strutinsky calculations.

An excitation function measurement has been performed over the laboratory range $52--94\phantom{\rule{0.3em}{0ex}}\text{MeV}$ investigating resonance phenomena in the single excitation $^{16}\mathrm{O}$ $(^{16}\mathrm{O},{^{16}\mathrm{O}}^{*}\ensuremath{\rightarrow}^{12}\mathrm{C}_{\mathrm{g.s.}}+\ensuremath{\alpha})^{16}\mathrm{O}_{\mathrm{g.s.}}$ breakup reaction. A number of enhancements are observed in these excitation functions for excitation to the ${4}_{1}^{+}$, $10.35\phantom{\rule{0.3em}{0ex}}\text{MeV}$ and ${4}_{2}^{+}$, $11.09\phantom{\rule{0.3em}{0ex}}\text{MeV}$ excited states in $^{16}\mathrm{O}$. The overlap between these and previously measured enhancements is discussed. Excitation functions for the ${2}_{2}^{+}$, $9.84\phantom{\rule{0.3em}{0ex}}\text{MeV}$ and ${2}_{3}^{+}$, $11.52\phantom{\rule{0.3em}{0ex}}\text{MeV}$ excited states are also presented.

A study of the $^{12}\mathrm{C}$${(}^{20}$Ne${,}^{12}$${\mathrm{C}}^{16}$O${)}^{4}$He reaction has revealed $^{16}\mathrm{O}$${+}^{12}$C breakup from states in $^{28}\mathrm{Si}$. These states may correspond to highly deformed shape isomeric configurations.