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The present paper identifies unique symmetry properties of the [ital [rvec d]]+[ital d][r arrow][ital d]+[ital p]+[ital n] breakup reaction that make it an excellent probe for studying charge-symmetry breaking. Measurements were made for two configurations of the ejected particles in the breakup reaction to obtain values of the spin observables [ital A][sub [ital y]], [ital A][sub [ital y][ital y]], and [ital A][sub [ital z][ital z]]. These observables are compared for the mirror reactions [sup 2]H([ital [rvec d]],[ital dp])[ital n] and [sup 2]H([ital [rvec d]],[ital dn])[ital p] for the two angle pairs ([theta][sub [ital d]],[phi][sub [ital d]],[theta][sub [ital N]],[phi][sub [ital N]])=(17.0[degree],0[degree],17.0[degree],180[degree]) and (17.0[degree],0[degree],34.5[degree],180[degree]) for an incident deutron energy of 12 MeV. In addition, spin observables for the [sup 2]H([ital [rvec d]],[ital pn])[ital d] reaction at [theta][sub [ital p]]=[theta][sub [ital n]] and [phi][sub [ital p]]=[phi][sub [ital n]]+180[degree] are shown to provide a particularly good test of charge symmetry. Our [ital A][sub [ital y]], [ital A][sub [ital y][ital y]], and [ital A][sub [ital z][ital z]] data for the [sup 2]H([ital [rvec d]],[ital pn])[ital d] reaction at ([theta][sub [ital p]],[phi][sub [ital p]],[theta][sub [ital n]],[phi][sub [ital n]])=(17.0[degree],0[degree],17.0[degree],180[degree]) are used to illustrate this latter point. Of the ten charge-symmetric sets of observables measured, two were foundmore » to differ by 2.5 standard deviations.« less

In this paper we review the results of a series of high-accuracy measurements on the neutron-deuteron (n-d) scattering system at incident neutron energies below 20 MeV. These measurements were designed to: 1) provide data of sufficient accuracy to be used to refine the parametrization of the nucleon-nucleon force, 2) to test the reaction dynamics in the “rigorous” calculations of three-nucleon (3N) breakup reactions, and 3) identify 3N scattering observables that are specifically sensitive to three-nucleon forces and/or off-shell effects. At TUNL we have measured vector analyzing powers Ay (θ) for n-d elastic scattering and the breakup reaction to an accuracy better than ± 0.005 and ± 0.020, respectively. Recent results on items 1) and 2) will be presented. Also, results of cross-section measurements for n-d and p-d breakup will be compared to a “rigorous” 3N calculation.

New absolute and relative cross sections for elastic scattering of electrons from the proton have been measured using the linac facilities at NIST. The data were obtained using a high-pressure, flowing-gas target cell alternately filled with H 2 and CH 4 gas. The measurements span a momentum transfer range from 0.22 to 0.73 fm −1 . These new results have been combined with an extensive set of existing elastic electron scattering data in a Fourier-Bessel analysis to obtain the charge density parameters and the rms radius of the proton. Some selection among the available data was necessary because of inconsistencies between published data sets. We obtain an rms radius of 0.865 ±0.020 fm.

Recently we have made kinematically incomplete and complete measurements of the vector analyzing powers Ay(8) for the n-p final-state interaction (FSI) in the n-d breakup reaction at 12 MeV. The kinematitally incomplete (KI) experimental arrangement, measuring the momentum of one outgoing neutron and the energy of the proton, permitted us to measure several breakup processes simultaneously to a high statistical aCCUracy and was therefore favored over the kinematically complete (KC) arrangement in which both outgoing neutrons were detected. Consequently, the KC measurements were conducted by parasiting on the KI experiment by adding a pair of neutron detectors at forward angles to detect the Second outgoing neutron. The incentives for performing the measurements are multiple. The investigation of polarization effects in the n-d breakup processes Should provide unique information about various aspects of the nuclear force acting in this three-nucleon system. As is well known, the predictions of Ay(e) for n-d elastic scattering at low energies are strongly Sensitive to the inclusion of the Pand D-wave interactions, while in Contrast, the description of the dlfferentlal cross section ~(8) data displays only slight sensitivity to the Pand D-wave interactions.l, 2 Because of the sensitivities observed in the Ay(8) data for elastic Scattering, it is likely that the Ay(8) data for the breakup processes Wlll exhibit sensitlvlties to aspects of the nuclear force that are SUpPressed in the a(8) data. Also, effects due to the three-nucleon force and charge-symmetry breaking might be revealed in such polarization data. The technique employed in these measurements used the pulsed polar~zed beam facilities at Triangle University Nuclear Laboratory (TUNL). The experimental setup is shown in Fig. I. The polarized neutrons were ~roduced via the 2H(~,~) source reaction, using the neutrons emerging at 0o. The incident deuteron beam was pulsed to enable the use of

Experimental methods to measure the vector analyzing powers over a broad range of kinematic configurations in the n-d breakup reaction have been developed at TUNL. These techniques employ the polarized beam facilities at TUNL and use the 2H( d , n )3He reaction as a source of low-energy polarized neutrons. Our methods permit measurements to a high statistical accuracy over a large fraction of three-nucleon phase space. The techniques are described and experimental spectra along with kinematic calculations are presented.

Experimental and theoretical cross sections are presented for the /sup 6/Li(/sup 3/He,/sup 3/He/sup 3/He)/sup 3/H and /sup 6/Li(/sup 3/He,t/sup 3/He)/sup 3/He reactions for the symmetric angle pairs 20/sup 0/-20/sup 0/, 28.3/sup 0/-28.3/sup 0/, and 35/sup 0/-35/sup 0/. The theoretical cross sections are calculated in a three-body model where the trions (i.e., mass-3 nuclei) are treated as elementary particles with /sup 6/Li being a /sup 3/He-/sup 3/H bound state. The trion-trion interaction is represented by S wave separable potentials with the breakup cross sections calculated with the tree-body Haftel-Ebenhoeh code. the Coulomb interaction is taken into account by fitting the separable potential parameters to the trion-trion scattering data and is included approximately in the breakup code. The experimental cross sections are compared with both the plane-wave impulse approximation and the three-body model predictions. The plane-wave impulse approximation predicts both the shapes and magnitudes poorly (10 to 20 times experiment). Without Coulomb corrections the three-body model gives good agreement with experiment for the shapes of the spectra with the magnitudes generally being about 40% of experiment for /sup 6/Li(/sup 3/He,/sup 3/He/sup 3/He)/sup 3/H and about 80% for /sup 6/Li(/sup 3/He,t /sup 3/He)/sup 3/He. The Coulomb corrections improve the magnitudes predicted by themore » three-body model but not the shapes. It is observed that for these reactions S wave separable potentials describe the breakup data much better than they do the two-body trion-trion scattering data. This result should encourage further three-body treatment of these and similar reactions.« less

The cross section and the analyzing powers Ay, Axx, Axz and Ayy for the reaction H ( d , 2 p ) n are studied by kinematically overdetermined measurements at an incident energy of 16 MeV at collinear and somewhat off-collinear kinematic conditions. A three-body Faddeev model using two realistic separable potentials that have different short-range parts gives a good fit to the data. Uncertainties in Coulomb corrections make it difficult to draw definitive conclusions about possible three-nucleon force effects at collinearity conditions.

Optical emission spectra from thin CsBr, Cu, and Ni films on a thick Al foil have been obtained with 100 keV Ar + ion bombardment. The photon emission from all samples showed a pronounced AlI peak, whose intensity was rising with bombardment time. For the CsBr thin film sample, the AlI line was superimposed on a continuum spectrum.

Two-spectator quasifree processes (graphs with two spectator particles) for the 3 He( 3 He, dd)pp reaction at the symmetric angle pairs θ = 30.1° at E 3 He = 50 MeV and θ = 37° at E 3 He = 78 MeV are investigated. The theoretical cross sections are calculated with the PWIA model. The measured cross sections are smaller but have shapes which are in good agreement with the calculation. The ratio N = experiment/theory is approximately 0.05 at 50 MeV and 0.1 at 78 MeV. The reaction 2 H(d, pp)nn also was studied at the symmetric angle pair θ = 34.8° and E 2 H = 34.7 MeV and the ratio is about 0.14.

Quasifree scattering and quasifree reaction processes have been examined in the 3 He+ 2 H → p+d+d, 3 He + 2 H → n+p+ 3 He and 3 He+ 2 H → p+p+t reactions. Beam energies of E d = 22.3 and 35 MeV and of E 3He = 30, 33.5, and 52.5 MeV were used. The experimental results are compared with PWIA calculations and Fourier transforms of the wave functions are extracted. The quasifree processes are described qualitatively by the PWIA, but some features cannot be described by either PWIA or DWIA.

The sputtering yield, joint polar and azimuthal angular distributions and the energy distribution of atoms sputtered from copper single crystals by 100 keV copper ions has been calculated as a function of crystal orientation using the cascade simulation code MARLOWE. The calculated yields and angular distributions are compared with experimental results for ions incident parallel to a close-packed axial channelling direction, parallel to a plane, and along a pseudo-random direction. Significant channeling effects are exhibited in both calculations and experiment. Strong peaking in the backscattered direction is calculated and observed for the axial irradiations alone. Primary range distributions and damage profiles are calculated for the three crystal orientations and compared with lattice damage measurements. The distributions of sputtered ions in both energy and angle are presented.

The4He(\(\vec d\),pα)n cross section, vector and tensor analyzing-power data with 12 and 17 MeV deuterons at kinematic conditions including proton-alpha quasifree scattering, neutron-alpha and proton-alpha final-state interactions, as well as collinearity, are compared with the predictions of the three-body model using different nucleon-alpha and neutron-proton forces. In general, better two-body potentials give a better fit to the data, except for the vector analyzing-power data. The roles of the impulse and multiple-scattering amplitudes are studied to understand the sensitivity to two-body potentials and to understand the reason for the successes and the failures of the model.

Quasifree scattering and quasifree reaction processes have been examined in ten 3 H + 3 He and 3 He + 3 He reactions with at least two of the three or more final state particles being charged. Beam energies of 50, 65 and 78 MeV were used. The experimental results are compared with PWIA predictions and Fourier transforms of the wave functions are extracted. The quasifree processes are described in a consistent, but qualitative, manner by the PWIA; distortion in the intial state appears to be the cause of the consistent deviation of the data from the PWIA predictions. Extracted values for the 3 H(d, 3 He)2n cross section are given.

Copper targets were implanted with 125 keV gold and tantalum ions at selected incident angles of the beam relative to the target normal to examine the effect of the incident angle on the sputtering yields, the dose retained in the modified layer, and the atomic surface fractions. Sputtered particles were collected on aluminum foils to measure the angular distribution of the sputtered particles and to determine the partial sputtering yields of the beam and target species. A 1.5 MeV xenon beam implanted markers into the copper targets to determine the average sputtering yield for the surface during the implantation. Theoretical predictions from a surface binding energy correction model were compared with the experimental results. Although the predictions from the model were not exact, the trends of the data were in agreement with the model. The measured total sputtering yield increases with increasing incident beam angle, and, correspondingly, the fluence retained decreases with incident beam angle.

The sputtering yield and the angular distribution of sputtered atoms have been measured as a function of copper-ion-beam orientation with respect to copper single-crystal targets. Alpha-particle channeling has been employed to measure the lattice damage induced during the sputtering experiments. The experimental results have been compared with results from the cascade simulation program MARLOWE. Both planar and axial channeling of incident ions have been shown to significantly reduce the sputtering yield relative to a psuedo-random irradiation direction. Channeling of the incident particles also increases the depth to which lattice damage is produced. Surface preparation is found to strongly influence the orientation effects, with mechanical polishing reducing the channeling of incident ions, relative to electropolishing.

The applicability of the particle induced x-ray emission (PIXE) in the determination of sputtering distributions and yields was studied. Sputtered particles were caught on foils for the 45 keV to 125 keV self sputtering of Fe, Ni, Cu, Ti, Mo and Au and for the 90 keV sputtering of both target and implanted particles of Ni+ + Cu, Cu+ + Ni, Ni+ + Fe, and As+ + Ag, and for the target particles of Ar+ + Au. Sputtered particles were collected in an ultra high vacuum (UHV) and in a poorer vacuum system with 99.99% pure Al catcher foils. PIXE data, the x-ray yields from 1 MeV proton and 2 MeV alpha particle beam bombardments, were used to determine the angular distribution of the sputtered products. The sputtering yield was calculated from the angular disbution data by integration over a hemisphere assuming azimuthal symmetry. The efficiency of the PIXE systems was calibrated with a standardized target such as 18 ?g/cm2 Fe on the same 99.99% Al foil material. The Al x-ray yield of the catcher foils provided a normalization of all data from a given catcher foil. For a number of samples studied, we have been able to compare the distribution and yields obtained with PIXE to those measured by the Rutherford backscattering (RBS) technique. Also separate RBS analysis of Xe markers in the sputtering targets provided yield values. Comparision of the PIXE and RBS results indicate that the PIXE sputtering distribution and yield measurements are comparable.

The cross section and the analyzing powers A y , A xx and A yy for the reaction 4 He( d , αp)n are studied with kinematically complete measurements at incident energies of 12 and 17 MeV. Spectral structures due to the final-state interactions and quasifree scattering are measured. A three-body model of the Faddeev type gives a satisfactory fit to the cross-section and A y data, but it fails to fit adequately the tensor analyzing-power data. The tensor analyzing powers in the breakup process should be sensitive to the input two-body force, and that sensitivity seems to be somewhat greater near the three-body 1 + resonance.

During 250 keV Ar+ ion bombardment of an Cr/Ni sandwich on Si samples [1] X-ray and optical emissions have been recorded. The optical spectrum showed pronounced Cr I lines from the first Cr layer of the bombarded sample. The X-ray spectra showed Ar K. lines. The Al foils bombarded by 100 keV Ar+ ions showed the optical line spectra with pronounced Al I optical lines as well as Al II and Al III optical lines, while the X-ray spectra obtained by 250 keV Ar+ ion bombardment showed pronounced K X-ray Al lines and less pronounced K X-ray argon lines. The correlation diagram for the Ar+→ Cr collisions shows that the Ar 1s electron can be promoted to the 2p levels of the united atom with a probability of vacancy creation in the Ar K shell. The Al Kα lines appeared as a consequence of the Al Is electron promotion to the 2p level of the united atom. The promoted Al Is electron left a vacancy in the Al K shell. Deexcitation in both the Ar and Al excited atom occurs when the K vacancy is filled by an electron from the upper shells.

Surface barrier detectors can measure the characteristics of neutron fields and related light-ion fluxes (LIF). Some of us have shown that a photodiode, with a suitably chosen radiator, can measure fluences of monoenergetic neutrons and have studied the shapes of a few continuous neutron spectra. Others have used silicon detectors to measure the energy of neutrons from reactions. We have attempted to perfect a simple, compact and inexpensive single surface barrier detection system to measure both the intensities and approximate spectral shape of continuous neutron and LIFs. We have measured such fluxes for three known collimated and uncollimated neutron beams with two geometrical configurations and with at least two different thicknesses of CH2 and CD2 radiators. All neutron flux data were obtained with a Au shield in front of the detector; this was removed for LIF measurements. The known shapes of the impinging neutron beams were used to calculate the expected recoil-particle spectra and such predictions have been compared with the experimental data. Also, data have been obtained with telescopes, with carbon foil and thin detector-grade silicon foil radiators. These data allow us to estimate contributions to the higher-energy portion of the recoil-particle spectra from reactions due to the carbon in the CH2 and CD2 radiators and due to the silicon in the detector. Corrections for rim effects in the detector and multiple scattering in the radiator are calculable.

Self-ion sputtering yields were determined for copper, nickel, and aluminum at 60 keV, 90 keV, and 120 keV. The sputtering yields were determined by Rutherford backscattering measurements of the energy shifts of a deeply implanted xenon marker layer and by measuring the distribution and amount of sputtered material on a catcher foil using backscattering and particle induced X-ray emission. The effect of dose rate and net fluence on the yield were examined. Optical monitoring of the light intensity emitted by the sputtered particle confirmed no measurable change in the yield using self ion bombardment. The self-ion sputtering yields measured in this study are less than predicted by theory but are self consistent within experimental error independent of measurement technique. Additional measurement of self-ion sputtering yields in this energy range are needed for applications in materials modification.

A variety of analyzing powers for d + p breakup reactions initiated by polarized deuterons incident on protons have been measured at deuteron bombarding energies of 16 and 79 MeV. The results are compared with Faddeev calculations using both separable (at 16 and 79 MeV) and local (at 79 MeV) interactions. These calculations include nucleon-nucleon forces in the S, P and D states and the 3S1−3D1 tensor force.

In this paper the surface binding energy model proposed by Reynolds for a binary alloy has been extended to a ternary system. From this model extension the steady state atomic surface fractions were calculated for a ternary surface alloy to be prepared by ion implanting a binary alloy of known composition. These predictions were compared with the results of the subsequent ion implantation experiments. The total implantation process was monitored by the observation of light emitted through de-excitation processes from sputtered neutral atoms. The experimental results reported are for nickel-chromium alloy implanted with 90 keV copper and tantalum and were analyzed using Rutherford backscattering, particle induced X-ray emission, and Auger surface analysis. From these results the partial sputtering yield for each component, net sputtering yield and surface atomic fractions were determined, and then compared with the predicted values. The different analytical techniques show consistent agreement within experimental error and there is reasonable agreement between the experimental results and the predicted values.

The 7 Li (α, t) 8 Be (α) 4 He and 7 Li (α, α') 7 Li ∗ ( t ) 4 He reactions have been observed in a kinematically complete experiment with E α = 50 MeV, particle identification, and on-line computer coincidence electronics. Sequential decay through the ground, 2.9, 11.4, 16.6 and 16.9, and 19.9 MeV states of 8 Be and the 4.63 and 7.48 MeV states of 7 Li has been observed. Triton angular distributions for the decay through the ground state of 8 Be were obtained with and without coincidence requirements. Agreement of these distributions implies isotropic decay in the c.m. of the 8 Be ground state. The contribution of quasi-elastic processes is small due to the specific limited portion of phase space observed.

Approximately seventy resonances were observed for the $^{56}\mathrm{Fe}(p,\ensuremath{\gamma})^{57}\mathrm{Co}$ reaction in the range of proton energy from 1300 to 1800 keV. Gamma-ray energy measurements performed with scintillation and lithium-drift silicon spectrometers yield 6.040\ifmmode\pm\else\textpm\fi{}0.030 MeV for the $Q$ value of the $^{56}\mathrm{Fe}(p,\ensuremath{\gamma})^{57}\mathrm{Co}$ reaction and show the existence of intermediate states in $^{57}\mathrm{Co}$ at 1.381\ifmmode\pm\else\textpm\fi{}0.010, 1.506\ifmmode\pm\else\textpm\fi{}0.020, 1.760\ifmmode\pm\else\textpm\fi{}0.020, 1.921\ifmmode\pm\else\textpm\fi{}0.020, 2.136\ifmmode\pm\else\textpm\fi{}0.020, 2.60\ifmmode\pm\else\textpm\fi{}0.03, 2.74\ifmmode\pm\else\textpm\fi{}0.03, 2.80\ifmmode\pm\else\textpm\fi{}0.03, 2.88\ifmmode\pm\else\textpm\fi{}0.03, 3.11\ifmmode\pm\else\textpm\fi{}0.03, 3.18\ifmmode\pm\else\textpm\fi{}0.03, 3.27\ifmmode\pm\else\textpm\fi{}0.03, and 3.52\ifmmode\pm\else\textpm\fi{}0.03 MeV. Triple-correlation measurements performed with a double sum-coincidence spectrometer permit ${J}^{\ensuremath{\pi}}$ assignments of ${\frac{3}{2}}^{\ensuremath{-}}$, ${\frac{5}{2}}^{\ensuremath{-}}$, ${\frac{5}{2}}^{\ensuremath{-}}$, and ${\frac{5}{2}}^{+}$ to the intermediate states in $^{57}\mathrm{Co}$ at 1.38, 1.76, 1.92, and 2.14 MeV, respectively. These measurements were performed at resonance energies of 1525, 1598, 1622, 1637, 1645, and 1800 keV, where the capturing states at the 1637- and 1800-keV resonances are assigned a ${J}^{\ensuremath{\pi}}$ value of ${\frac{5}{2}}^{+}$, and for the others ${J}^{\ensuremath{\pi}}$ is ${\frac{3}{2}}^{\ensuremath{-}}$. Ambiguities exist for the $\frac{E2}{M1}$ amplitude ratios for all of the mixed secondary gamma-ray transitions observed in these studies. All measurements were in agreement with the established value of ${\frac{7}{2}}^{\ensuremath{-}}$ for the ground state of $^{57}\mathrm{Co}$.

The spectra of gamma radiation following reactor-neutron capture in separated tungsten isotopes have been measured with a three-crystal scintillation pair spectrometer as well as with a single-crystal scintillation counter, and with both in coincidence. Energies and intensities of the gamma rays from product nuclei 183 W, 184 W, 185 W and 187 W are reported. From those gamma rays identified as ground-state transitions, the neutron binding energies of these four isotopes respectively are deduced to be 6.10, 7.48, 5.86 and 5.34 MeV. The presence of considerable high-energy structure in each of the spectra indicates that direct capture and/or anomalous resonance capture processes may be of importance.

Gamma-ray spectra, angular distributions and coincidence spectra have been studied in the reaction 8up(p, 7) 32S at bombarding energies of 355, 440 and 540 keV. Several cascades have been identified and branching ratios have been measured. The spins and parities of the 9.39, 9.29, 9.21 and 4.70 MeV levels in 3zS are found to be 2 c-), 1 +, (1 +) and 1 +, respectively. An extensive study of the reaction 31p(p, ~)32 S at the two lowest proton resonance energies was recently published by Nelson, Carlson and Schlenker 1). At about the same time, an oral report 2) on the same reaction including the third resonance was given by the present authors. As the two accounts differed in several respects, we have extended our investigations with particular attention to the analysis of the gamma-ray spectra and to the elimination of systematic errors in the angular distribution measure- ments. We have verified the spin assignments of Nelson, Carlson and Schlenker for the 9.21 and 9.29 MeV levels, and made a new assignment for the 9.39 MeV level. The gamma-ray decay, particularly at the second proton resonance, is considerably more complex than previously reported. In particular, one of the angular correlation measurements made by Nelson, Carlson and Schlenker must be re-interpreted, such that the spin value of 1 + which they reported for the 4.47 MeV state should instead be attributed to the 4.70 MeV state in 32S.

The quasielastic scattering of 50-MeV $\ensuremath{\alpha}$ particles has been used as a tool to study the cluster configurations of the $^{6}\mathrm{Li}$ nucleus by means of the $^{6}\mathrm{Li}(\ensuremath{\alpha},\ensuremath{\alpha}x)Y$ reaction. Data have been obtained in kinematically complete experiments and at exact quasielastic angles for those cases corresponding to $x=p, d, t$, He, and $\ensuremath{\alpha}$. Analysis has been carried out in the framework of the plane-wave impulse approximation. Quasielastic cross sections have been measured and experimental momentum distributions extracted. Theoretical fits to these distributions using simple Gaussian and exponential functions have been calculated and used to determine both absolute and relative clustering probabilities with fair success. The more reliable relative probabilities indicate strong $p, d$, and $\ensuremath{\alpha}$ clustering in $^{6}\mathrm{Li}$ and rather weak $t$ and $^{3}\mathrm{He}$ clustering.

Approximately 50 resonances having a yield of greater than 100 gamma rays per μC were discernible from the 62Ni(p, γ)63Cu reaction in the range of proton energy from 1100 keV to 1850 keV. Gamma-ray energy measurements obtained by utilizing scintillation and lithium-drifted silicon spectrometers yield 3.42±0.02 MeV and 6.14±0.02 MeV for the Q-value of the 58Ni(p, γ)59Cu and 62Ni(p, γ)63Cu reactions, respectively. The existence of intermediate states was observed in 59Cu at 0.49±0.01, 0.91±0.01, 1.38±0.02, 2.00±0.02 and 2.32±0.02 MeV; and in 63Cu at 0.67±0.01 and 1.55±0.02 MeV. Triple-correlation measurements were performed with a double sum-coincidence spectrometer at resonance energies of 1424, 1663 and 1715 keV for the 58Ni(p, γγ)59Cu reaction and at resonance energies of 1374, 1414, 1507 and 1634 keV for the 62Ni(p, γγ)63Cu reaction. These measurements permitted Jπ assignments of ( 1 2 ), 5 2 − , 5 2 − , 5 2 − and ( 3 2 − ) or ( 5 2 − ) to the intermediate states in 59Cu at 0.49, 0.91, 1.38, 2.00 and 2.32 MeV, respectively; and ( 1 2 ) and either ( 3 2 − ) 5 2 − ), or ( 3 2 + ) to the intermediate states in 63Cu at 0.67 and 1.55 MeV, respectively. The E2/M1 amplitude ratios were obtained whenever possible from the correlation data.

The 7 Li (τ, α) 6 Li and 7 Li(τ, α) 6 Li∗(d) 4 He reactions have been used to study the energy levels of 6 Li. Singles spectra provide evidence for five states below 6 MeV of excitation energy. These include the ground state and four excited states at 2.18, 3.56, 4.57 and 5.36 MeV. One- and two-parameter coincidence data confirm the identification of these levels and aid in the determination of decay modes and isospin assignments. The deduced isospin assignments for the five levels are T = 0, 0, 1, 0 and 1 with a small T = 0 impurity, respectively.

The (α, α') and (p, p') reactions have been used to populate states in 24 Mg in order to measure lifetimes of ten states by the Doppler-shift attenuation method. The shifted γ-rays were observed by a planar 5.6 cm 3 Ge(Li) detector at 90° to the beam at the target in coincidence with the scattered particles observed in either of two particle detectors located symmetrically with respect to the beam. A computer coupled dual two-parameter arrangement permitted concurrent measurements for all states appreciably populated. The present measured transition probabilities are compared with predictions from a truncated j - j coupling shell-model calculation.

The α-α angular correlation from the sequential decay of the 11 B(p,α) 8 Be 2.9 (α) 4 He reaction indicates that this reaction proceeds by compound-nucleus formation of 12 C states of E x , J π = 16.11(2 + ), 16.58(2 − and 17.23(1 − ). For E p = 0.163, 0.675, 1.00 and 1.39 MeV, and for a first-emitted α-partiele angle of 90°, kinematically complete experiments provide observed symmetry axes for the 8 Be 2.9 break-up distribution in its own c.m. system. The axis for each correlation function, when compared to the momentum transfer and recoil directions associated with various possible mechanisms, indicates that compound-nucleus formation is the predominating mechanism at each beam energy. The correlation functions at the resonant proton energies of 0.163, 0.675 and 1.39 MeV are consistent with the capture states having J π = 2 + , 2 − and 1 − , respectively.

The sputtering yield can be determined for thin films on a much thicker substrate by sputtering the film material completely. Optical emission intensities for spectral lines from the thin film and substrate elements can be measured as a function of the incident ion fluence. Thin Cu, Ni and Mn films of 17 μg/cm2, 22 μg/cm2 and 28 μg/cm2 on thick Al substrates have been sputtered by 100 keV Ar+ ions with current densities of less than 2 μA/cm2. The Cu I, Ni I, Mn I and Al I optical lines were used to determine the sputtering yields.

The $sup 2$H(p,2p)n reaction has been investigated under the special kinematic condition that the neutron is at rest in the center of mass. A comparison of experiment and theory is used to examine the significance of the spectral structure observed for such collinearity conditions. (AIP)

A system to simultaneously measure Auger-electron, X-ray and optical emissions, induced by 100–400 keV heavy ions from surfaces, has been designed, constructed and tested. The Auger spectrometer is a rotatable, 30°-entrance-angle, parallel-plate electron energy analyzer with a channeltron detector and it has a resolution of 0.29%. The X-ray and optical emissions are measured with a standard Si(Li) PIXE detector and electronics and with a Jarrell-Ash monochrometer, respectively. Preliminary data are presented.

The sputtering yields from thin Cu films of various thicknesses on aluminum backings, with 180 keV Ar+ ions, have been determined. The evolution of the ion-induced optical emission from the substrate, used to determine the ion dose necessary to sputter the film, was compared with predictions from the EVOLVE code for similar film thicknesses and sputtering conditions. The data and the predictions coincide for a 200 A film. For thicker films, they are similar but don't overlap. The sputtering process is well described by the EVOLVE code. For two of the films the experimental yield values are slightly lower than the predictions from the code, but the results, both experimental and from the simulation, are consistent with the idea that for very thin films the yield is smaller than that of infinitely thick targets and decreases as the film thickness decreases.

The alpha induced deuteron breakup reactions have been of interest since the nucleon induced deuteron breakup problem was addressed with tractable and predictive models based on the Faddeev formalism and with appropriate nucleon-nucleon forces. In this paper we discuss a few special features of the alpha induced deuteron breakup reactions. Specifically, we point out the importance of the n-p tensor force in the predictions of the three-body model that fit the tensor analyzing powers better and the concomitant deterioration of the fit to the vector analyzing power caused by the inclusion of the tensor force. We suggest that there exists evidence for the 1S0 n-p interaction, which is isospin forbidden, in both the cross section and spin observables data. Finally, we discuss certain characteristics of the p-? quasi-free-scattering and n-? final-state-interaction processes.

Sputtering yields and angular distributions have been measured as functions of sample preparation techniques and incident ion-beam orientation with respect to the crystal axes for 100 keV Cu-ion beams on Cu crystals and polycrystalline samples. The angular distributions have structure requiring an n th order cosine with two Gaussians superimposed to fit the data; strong peaking is observed near the backscatter direction. The yield is dependent on the beam to crystal and beam to polycrystalline-rod axis orientation, on the grain size of the polycrystals and on sample-preparation techniques. Yield measurements vary by as much as a factor of 4. Lattice-damage differences, measured with alpha particle channeling, are much smaller and seem to be saturated by fluences of the order of 1 × 10 16 /cm 2 .

On-line measurement of the degradation of a small set of commercial LED devices bombarded with a 15 MeV median energy neutron beam has been obtained. During irradiation the light output of an LED was recorded via a fiber optic link to an external area free of radiation where a photodiode detector viewed the fiber optic signal. All data were recorded on DVMs, on chart recorders and on magnetic tape with an on-line computer. The data for each LED can be described by one primary damage function and the amount of damage is rather strongly dependent on the amount of phosphorous in the GaAsP LEDs studied. The neutron energy distribution and intensity are well known from previous dosimetry measurements. Radiographic data determined that a homogeneous spatial distribution of neutron flux is used. The neutron beam was uniform over the dimension of the samples and 2 × 1010 neutrons/cm2/sec are easy to obtain.

The atomic simulation code EVOLVE is used to calculate the fluence-dependent sputtering yield of a 200 A thick Cu film bombarded by 180 keV Ar atoms incident at 50° with respect to the target normal. The EVOLVE code has also simultaneously calculated the fluence-dependent compositional changes in the target which had bulk Al backing behind the Cu film. Comparison of the calculational results with the experimentally available Cu total sputtering yield and Al differential sputtering yield measurements shows good agreement.

In recent years computer simulations, experimental observations and analyses of the collected sputtered products from the interaction of ion beams on solid materials have demonstrated the sensitivity of the sputtering process to the surface characteristics of the material being investigated or modified. The usual characterization of the target material has been a post bombardment analysis of the surface for the relative concentration of the implanted atoms compared with the initial target components coupled with an examination of the profile of the implanted atoms in the surface region. Recent experiments have collected sputtered products during ion implantation and have compared the distribution of sputtered particles with theory. Techniques have been developed to measure the partial and net sputtering yields from the amount of material collected on the foils in these experiments. Typically the evaluation of the target material and the collected sputtered products has been reported for the steady state conditions during ion implantation. Our experimental group has chosen to evaluate the sputtering process from the onset of ion bombardment through the steady state condition. From these experiments models have been proposed for the behavior of the surface composition and the sputtering yields. Techniques developed for monitoring of the surface have provided data supporting the concept that the average surface binding energy of the bombarded target material is sensitive to the sputtering process. Calculating the manner in which the surface binding energy will change with the developing atomic surface fraction can qualitatively lead to more precise prediction of implantation requirements.

Publisher Summary This chapter reviews the N–P Final State Interaction (FSI) angular distribution in deuteron breakup at 45 MeV. An experiment described in the chapter was performed to provide an FSI angular distribution at energy higher than previously available. The experiment was performed with the NRL Sector Focusing Cyclotron using standard coincidence electronics for kinematically complete experiments. The chapter presents a comparison of the data with the results of calculations using several S-wave separable potentials tailored to test for sensitivity to off-shell and on-shell effects. These potentials have been described previously. The potentials have two different form factors A and B: A has off-shell behavior similar to that of the Reid soft core potential while B has off-shell behavior resembling the softer Yamaguchi. The potentials fit two different sets of phase shifts: set 1 corresponds nearly to experimental p–p 90° cross sections and set 2 corresponds to cross sections less than the p–p experimental values at energies above 10 MeV. The results, when put in the context of previous experiments and calculations, emphasize that there are still some basic factors not being considered in deuteron breakup calculations.

Publisher Summary This chapter examines the double spectator process in the 3He(3He,dd)pp reaction. Measurements of nuclear systems with three or four particles in the final state can be influenced by a number of processes: (1) quasifree scattering (QFS), (2) quasifree reactions (QFR), (3) final state interactions (FSI), (4) simultaneous breakup, which results in phase space distribution of events, and (5) second-order effects. The chapter describes an investigation on the four-body continuum for the reaction 3He(3He,dd)pp with two detector-telescopes in coincidence to determine whether the double quasifree scattering (DQFS) process is observable. The 3He(2H,dd)p and 2H(3He,dd)p reactions were also measured for DQFS-equivalent d–d center of momentum conditions with proton spectators in the target and projectile, respectively. The results obtained suggest that the DQFS process is observable, and the comparison of the data to PWIA predictions indicate that 3He has a reasonably strong p + d cluster configuration and that a PWIA analysis is as appropriate for DQFS processes as it is for QFS processes.

Publisher Summary This chapter explores a few nucleon reactions for mass fields greater than three. The majority of these experiments are being done to investigate quasi-free (QF) processes with all possible pairs being observed, including both QF scattering and QF reactions. An important question being addressed is to what extent distorted waves improve the impulse approximation predictions. In few cases, substantial improvements are obtained using distorted waves, but in the tightly bound alpha particle, evidence that plain waves are as appropriate as distorted waves exists. An experimental situation that can cause problems is the spectral structure as a result of 4He excited states. This can cause severe problems with n–n scattering-length experiments, and the success or failure of these experiments can depend upon preselecting the most advantageous regions of phase space. Also, Coulomb FSI occurs in few of these experiments, and this FSI can produce dramatic reductions in the observed cross sections. This effect occurs when two charged particles have almost zero relative energy and no threshold resonance structure. The Coulomb repulsion can dominate, causing a striking dip in the cross section and can interfere with the investigation of other processes.

This chapter discusses quasi-free processes in the 2 H+ 3 He reactions. In the interaction between 3 He and 2 H, there are several three-particle breakup combinations possible. Kinematically, complete measurements were obtained with 2 H beam energies of 22.3 and 35 MeV and 3 He beam energies of 30.0, 33·4, and 52.5 MeV. Charged particle pairs were detected with conditions favoring the observation of quasi-free processes, both quasi-free scattering (QFS) and quasi-free reactions (QFR). The d + d, p + d, and 3 He + p QFS interactions and the 3 He + n→ p + t, d + d → p + t, and 3 He + n → d + d QFR interactions were observed. The chapter presents the analysis of data for a given interaction and comparison of a plane-wave-impulse-approximation prediction. The momentum wave function is extracted for small values of spectator momentum. Data were acquired primarily with a gas cell target having either 2 H or 3 He gas and fixed detector-aperture geometry. The results indicate that there is little difference in d 3 σ (exper)/d 3 σ (PWIA) as a function of beam energy (incoming channel CM energy), and this ratio does not depend on whether the spectator is in the projectile or in the target.

This chapter discusses quasi-free processes in the reaction 3 He + 3 He for E 3He = 50, 65 and 78 MeV. There are several three-particle breakup combinations that can occur when 3 He bombards 3 He. Measurements for a number of quasifree scattering (QFS) and quasifree reactions (QFR) interactions for 3 He + 3 He have been obtained in kinematically complete experiments. Charged particle pairs are detected and conditions are chosen favoring the observation of quasifree processes. The data are analyzed in terms of the plane-wave-impulse-approximation with the Hulthen wave function. In a study described in the chapter, gas cell target and fixed detector-aperture geometry was used. The effective target thickness and detector solid angles were calculated. The calculations were compared to measurements of the product of these parameters from 2 H(p,p) 2 H and 2 H(p,pp)n two- and three-body reactions for E =22 MeV where the d 2 σ and d 3 σ are well known.

Publisher Summary This chapter describes that in a coplanar, kinematically complete experiment, the evidence for a strong p–d final state Coulomb interaction (FSCl) was observed with the 2 H(α, dt) 1 H reaction. Identified particle and coincidence energy information for d and t with various angle pairs was obtained. Such an experiment has the distinct advantages of determining the kinematics of the final state and of distinguishing the final state interaction of interest from other interactions and sequential or quasi-free scattering processes. These advantages have made the application of the Watson–Migdal formalism and other appropriate formulations quite successful in predicting the shape of the spectral structure. In this particular experiment, comparison of theoretical predictions to the data is constrained by the low counting rates encountered and the presence of spectral structure. Though the chapter does not explain the three-body final state cross section for multiparticle breakup experiments with sequential and FSI processes, it explains the factors that contribute to the cross section. The presence of sequence and the insensitivity of the fitting to the effective range parameters limit the interpretation of the p–d FSI. The fits generated suggest that no 3 He excited state exists near its p–d breakup threshold.