Recent Articles

RAPID COMMUNICATION

Cross sections for the reaction ${}^{16}O (γ, p_{0}) {}^{15}N$ at forward angles for $E_{γ} = 80$ MeV

B. Schoch, H. Göringer, P. Jennewein, F. Klein, G. Lührs, and F. Zettl

Phys. Rev. C 22, 2630(R) (1980) - Published 1 December, 1980

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Via the reaction ${}^{16}O (e, p_{0}) {}^{15}N$ cross sections for the transition ${}^{16}O (γ, p_{0}) {}^{15}N$ have been extracted at angles $θ_{p} = 5 ° - 40 °$ . Whereas a modified quasideuteron model fails to describe the data, a calculation of Gari and Hebach with the inclusion of spin currents comes close to the results.

NUCLEAR REACTIONS ${}^{16}O (e, p_{0}) {}^{15}N$ , $E_{e} = 80$ MeV, measured $σ_{e} (E_{e}, θ)$ , deduced $σ_{γ} (E_{γ}, θ)$ ; BeO target.

RAPID COMMUNICATION

Forward-angle proton spectra in the continuum from the ${}^{58}{Ni} (p, x p)$ reaction at 100 MeV

A. A. Cowley, C. C. Chang, and H. D. Holmgren

Phys. Rev. C 22, 2633(R) (1980) - Published 1 December, 1980

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Forward-angle proton energy spectra in the continuum were measured for the reaction ${}^{58}{Ni} (p, x p)$ at 100 MeV with a plastic scintillator used as an active collimator. With this system it was possible to take measurements at angles as small as 8°. It was found that a previously observed broad peak in the continuum, which is suspected to appear as a result of a quasi-free nucleon-nucleon scattering, becomes even more pronounced as the scattering angle decreases. The active collimators were essential in eliminating contributions due to the penetration of collimator edges by elastically scattered protons. At small angles such effects can obscure the quasi-free peak.

NUCLEAR REACTION ${}^{58}{Ni} (p, x p)$ , $E_{p} = 100$ MeV; $θ_{L} = 8 ° - 25 °$ , measured $\frac{d^{2} σ}{d Ω d ε}$ .

RAPID COMMUNICATION

Hypervirial theorems and the Breit-type recoil correction for pionic atoms

J. L. Friar

Phys. Rev. C 22, 2636(R) (1980) - Published 1 December, 1980

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Hypervirial theorems are developed for the Klein-Gordon equation, which allow the Breit part of the pionic atom recoil correction (including the nuclear finite size) to be recast exactly into a form similar to the results for the Dirac equation. This form facilitates both numerical calculation and interpretation.

NUCLEAR STRUCTURE Pionic atoms, finite size, recoil correction, hypervirial theorems.

RAPID COMMUNICATION

Pion-nucleus charge exchange reactions at low energies

Gerald A. Miller and James E. Spencer

Phys. Rev. C 22, 2639(R) (1980) - Published 1 December, 1980

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Elastic charge exchange cross sections are calculated using the Kisslinger and Michigan State University potentials. Each is consistent with elastic sccattering data, and predicts observable charge exchange cross sections. However, the charge exchange cross sections obtained by the two models have substantial differences.

NUCLEAR REACTIONS ${}^{208}{Pb} (π^{+}, π^{-}) {}^{208}{Po}$ (double analog); cross sections predicted for 50 MeV $π^{+}$ .

RAPID COMMUNICATION

$E 2$ interference terms in the Coulomb excitations of the Os and Pt nuclei

H. L. Yadav, B. Castel, and H. Toki

Phys. Rev. C 22, 2644(R) (1980) - Published 1 December, 1980

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The sign of the $E 2$ interference term in the Coulomb excitation of the $2_{1}^{+}$ state in the even Pt nuclei is known to be in contradiction with the existing model calculations. This "sign anomaly" is examined in the framework of the extended asymmetric rotor model where it is shown that the $2 - q p$ exictations and their coupling to the collective states are essential for a proper description of the sign.

NUCLEAR STRUCTURE Coulomb excitation; asymmetric rotor model; nuclear structure of Pt isotopes.

${}^{2}H (α, p α) n$ reaction between 9.735 and 11.30 MeV

S. S. Dasgupta, R. J. Slobodrian, R. Roy, C. Rioux, and F. Lahlou

Phys. Rev. C 22, 1815 (1980) - Published 1 November, 1980

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A kinematically complete experiment has been performed to study the deuteron breakup by $α$ particles at six incident energies between $E_{α} = 9.735$ and $E_{α} = 11.30$ MeV (3.245 to 3.77 MeV in c.m.), very close to threshold. The data show strong energy dependence. Final-state calculations with the $α p$ and $α n$ interactions provide only fair fits, but the addition of three-body forces produces a significant improvement.

NUCLEAR REACTIONS ${}^{2}H (α, p α) n$ , $E = 9.735 to 11.30$ MeV; measured $σ (E_{p}, θ_{p}, θ_{α})$ : gas target.

Widths of ${}^{11}B$ levels below 9.0 MeV

R. Moreh, W. C. Sellyey, and R. Vodhanel

Phys. Rev. C 22, 1820 (1980) - Published 1 November, 1980

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The widths of nine energy levels in ${}^{11}B$ at 2.125, 4.445, 5.021, 6.743, 6.793, 7.286, 7.978, 8.559, and 8.920 MeV were determined by carrying out self-absorption and photon scattering measurements. The temperature variation of the scattering cross section was measured at $T = 298$ K and $T = 730$ K to study in some detail the effective temperature $T_{e}$ of ${}^{11}B$ in $B_{4}$ C, BN, and elemental B. The influence of $T_{e}$ on the deduced values of the radiative widths of ${}^{11}B$ is discussed.

NUCLEAR REACTIONS ${}^{11}B (γ, γ^{'})$ , $E = 10.3$ MeV bremsstrahlung. Deduced $Γ_{0}$ , effective temperatures. BN, $B_{4}$ C, B natural targets.

${}^{12}C (p, n) {}^{12}N$ reaction at 99 MeV

J. N. Knudson, B. D. Anderson, P. C. Tandy, J. W. Watson, R. Madey, and C. C. Foster

Phys. Rev. C 22, 1826 (1980) - Published 1 November, 1980

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Cross sections were measured for ${}^{12}C (p, n) {}^{12}N$ reaction at 99.1 MeV for nine laboratory angles between 0° and 48.5°. Two detector stations were used: one at 68.0 m was for angles between 0° and 24.5°, the other at 76.3 m for angles between 24° and 48.5°. Overall energy resolutions of 260 and 230 keV for neutrons of about 80 MeV were achieved at the first and second detector stations, respectively, with large-volume mean-timed counter assemblies. Cross sections for the ${}^{12}N$ ground state ( $1^{+}$ ) and 0.96 MeV state ( $2^{+}$ ) are compared with a distorted-wave impulse approximation calculation using an effective nucleon-nucleon interaction derived from nucleon-nucleon scattering data. For the ground state, the magnitudes of the calculated cross sections agree with the measured cross sections at forward angles but significantly underestimate the measured values beyond about 30°; for the 0.96 MeV state, the calculated cross sections must be reduced by 30% to obtain agreement with the cross sections measured at forward angles.

NUCLEAR REACTIONS ${}^{12}C (p, n)$ , $E = 99.1$ MeV; measured neutron spectra at nine angles between $θ = 0 ° and 48.5 °$ extracted $σ (E; θ)$ to 0.0 and 0.96 MeV states of ${}^{12}N$ . Compared angular distributions with calculations based on a nucleon-nucleon effective interaction.

Giant multipole resonances from inelastic scattering of 152-MeV alpha particles

F. E. Bertrand, G. R. Satchler, D. J. Horen, J. R. Wu, A. D. Bacher, G. T. Emery, W. P. Jones, D. W. Miller, and A. van der Woude

Phys. Rev. C 22, 1832 (1980) - Published 1 November, 1980

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Giant resonance spectra have been measured for ${}^{208}{Pb}$ , ${}^{120}{Sn}$ , ${}^{90}{Zr}$ , ${}^{58}{Ni}$ , and ${}^{46}{Ti}$ , using inelastic scattering of 152-MeV alpha particles. In addition to some low-lying states, the spectra were analyzed to yield separate peaks for the giant quadrupole resonance and giant monopole resonance, except in ${}^{46}{Ti}$ , where no evidence was found for a giant monopole resonance. The results for the monopole resonance when compared to distorted-wave Born-approximation calculations show that ∼100% (±20%) of the $T = 0$ , $L = 0$ energy weighted sum rule is depleted for nuclei with $A > 90$ . For ${}^{58}{Ni}$ only 40% of the monopole sum rule is found. The excitation energy of the giant monopole resonance follows the systematic trend $\sim 80 A^{- \frac{1}{3}}$ MeV. The data are also compared with folding model calculations using Tassie transition densities and an effective interaction derived from elastic data. Good agreement was obtained for low-lying quadrupole and octopole excitations, but this model yields considerably too little cross section for the monopole resonance. This probably indicates a deficiency in the Tassie model breathing mode transition density.

NUCLEAR REACTIONS ${}^{208}{Pb}$ , ${}^{120}{Sn}$ , ${}^{90}{Zr}$ , ${}^{58}{Ni}$ , ${}^{46}{Ti} (α, α^{'})$ , $E_{α} = 152$ MeV, $E_{χ} = 0 - 40$ MeV; measured $σ (E_{χ}, θ)$ ; discuss giant resonances, folding model calculations, deduced $L$ , $β_{L}$ .

Phenomenological model for elastic and inelastic scattering of high energy $α$ particles from nuclei

D. C. Choudhury

Phys. Rev. C 22, 1848 (1980) - Published 1 November, 1980

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A simple model within the framework of partial wave expansions in the adiabatic approximation is developed to calculate the elastic and inelastic scattering of high energy nucleons or composite systems of nucleons from nuclei. It is shown that the present model, apart from a multiplicative form factor depending on scattering angles and the nuclear surface thickness, is approximately equivalent to that of the diffractìon of waves by a black sphere of radius equal to that of the target nucleus in the Fraunhofer approximation. There appear two parameters in the formulation. One is the effective equilibrium radius of the target nucleus and the other is the effective thickness of the nuclear surface. The model is applied to analyze the recent experimental data from Saclay on the elastic and inelastic scattering of 1.37 GeV $α$ particles from ${}^{40, 42, 44, 48}{Ca}$ . It is found that the calculated differential cross sections of elastic and inelastic scattering and those measured experimentally are in very good agreement.

NUCLEAR REACTIONS ${}^{40, 42, 44, 48}{Ca} (α, α)$ , ${}^{40, 42, 44}{Ca} (α, α^{'})$ $E_{α}^{lab} = 1.37$ GeV. Calculated $σ (θ)$ and compared with experiments.

Effects of deformation on neutron total cross sections of even- $A$ Nd and Sm isotopes

R. E. Shamu, E. M. Bernstein, J. J. Ramirez, and Ch. Lagrange

Phys. Rev. C 22, 1857 (1980) - Published 1 November, 1980

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Neutron total cross sections of ${}^{144}{Nd}$ and ${}^{148}{Sm}$ and total cross-section differences for the pairs of isotopes ${}^{144, 142}{Nd}$ , ${}^{146, 144}{Nd}$ , ${}^{148, 144}{Nd}$ , ${}^{150, 144}{Nd}$ , ${}^{150, 148}{Sm}$ , ${}^{152, 148}{Sm}$ , and ${}^{154, 148}{Sm}$ have been measured at 25 energies from 0.75 to 14 MeV. Each sample consisted of about 40 g of powdered oxide with an isotopic enrichment >94%. For each isotopic pair the total cross-section difference was determined directly by measuring the ratio of transmitted flux for matched samples. This difference was found to have an oscillatory behavior when plotted as a function of incident neutron energy. The oscillations have been explained as a deformation effect qualitatively in terms of the nuclear Ramsauer effect and quantitatively using a deformed optical model potential. Adding two neutrons to a nucleus in this mass region was found to have a different effect on the neutron total cross section than adding two protons. A coupled channel analysis was performed using as input data the present total cross sections, low-energy neutron scattering parameters, and elastic and inelastic ( $2^{+}$ ) differential cross sections for neutron scattering at 4 and 7 MeV. Excellent total cross-section fits were obtained for the Sm isotopes; however, the total cross-section fits for the Nd isotopes were only fair. Quadrupole deformation parameters have been deduced for all the isotopes studied. The sensitivity of neutron total cross-section differences to this parameter and to the real isospin term of the nuclear potential is discussed.

NUCLEAR REACTIONS ${}^{142, 144, 146, 148, 150}{Nd}$ , $E_{n} = 0.75 - 13.89$ MeV, ${}^{148, 150, 152, 154}{Sm}$ , $E_{n} = 0.75 - 14.49$ MeV; measured $σ_{n, tot} (E)$ . Enriched targets. Deduced coupled-channel optical-potential parameters, quadrupole deformation parameters.

${}^{24}{Mg}$ ( ${}^{18}O$ , ${}^{16}O$ ) ${}^{26}{Mg}$ reaction at $E_{{}^{18}O} = 50$ MeV including scattering in entrance and exit channel

M. Bernas, F. Pougheon, M. Roy-Stephan, G. P. A. Berg, B. Berthier, J. P. Le Fèvre, and B. H. Wildenthal

Phys. Rev. C 22, 1872 (1980) - Published 1 November, 1980

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Cross section angular distributions of ${}^{24}{Mg}$ ( ${}^{18}O$ , ${}^{16}O$ ) ${}^{26}{Mg}$ reaction at 50 MeV incident energy leading to the first four excited states in ${}^{26}{Mg}$ and the elastic and inelastic scattering for ${}^{18}O$ + ${}^{24}{Mg}$ at 50 MeV and ${}^{16}O$ + ${}^{26}{Mg}$ at 56 MeV have been measured in order to investigate the reaction mechanism of the two-nucleon transfer reaction including the analysis of incident and exit channels. The measured angular distributions were analyzed in the framework of the exact finite-range distorted-wave Born approximation. Two neutron transfer amplitudes were determined using the $2 s - 1 d$ shell model amplitudes calculated by Chung and Wildenthal. The large experimental cross section in contrast to the smallness of the direct transfer amplitude and the peculiar shape of the measured angular distribution of the lowest $2_{1}^{+}$ state suggests that this level is mainly excited by two-step processes. It is shown that a coupled-channel Born approximation calculation describes successfully the angular distributions of the ground state and the $2_{1}^{+}$ state in ${}^{26}{Mg}$ .

NUCLEAR REACTIONS ${}^{24}{Mg}$ ( ${}^{18}O$ , ${}^{16}O$ ) ${}^{26}{Mg}$ , $E_{{}^{18}O} = 50$ MeV, measured $σ (θ, E_{x})$ ; ${}^{24}{Mg}$ ( ${}^{18}O$ , ${}^{18}O$ ) ${}^{24}{Mg}$ , $E_{{}^{18}O} = 50$ MeV and ${}^{26}{Mg}$ ( ${}^{16}O$ , ${}^{16}O$ ) ${}^{26}{Mg}$ , $E_{{}^{16}O} = 56$ MeV, elastic and inelastic scattering, measured $σ (θ)$ ; enriched targets; optical model parameters deduced from scattering: microscopic EFR-DWBA and CCBA analysis with shell-model wave functions.

Monte Carlo calculation of high-energy heavy-ion interactions

J. Cugnon

Phys. Rev. C 22, 1885 (1980) - Published 1 November, 1980

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A relativistic Monte Carlo model for high-energy heavy-ion collisions is presented. The interaction process is described as a sequence of classical, binary, on-shell baryon-baryon collisions. Pion production is taken into account by allowing $Δ$ resonance formation. The latter are given a definite mass and a lifetime larger than the collision time. They are, however, allowed to scatter or disappear by collisions with the nucleons. The results of the calculations are compared with experimental results for the inclusive proton and pion cross sections and two-proton correlations in the ${}^{12}C$ + ${}^{12}C$ , ${}^{20}{Ne}$ +NaF, and ${}^{40}{Ar}$ +KCl systems at 800 MeV per nucleon. The predictions of the model agree fairly well with the experimental measurements, except for the low-energy pion cross section, which is underestimated. The relation of this feature to the zero-width mass spectrum of the $Δ$ resonances is briefly discussed. The model is used to separate the direct knockout and the thermal contributions to the proton inclusive cross section. Attention is drawn to the fact that these two contributions are not unambiguously defined.

NUCLEAR REACTIONS High-energy heavy-ion collisions; Monte Carlo simulation; calculated proton and pion spectra for ${}^{12}C$ + ${}^{12}C$ , ${}^{20}{Ne}$ +NaF, and ${}^{40}{Ar}$ +KCl at $\frac{E}{A} = 800$ MeV.

Target fragmentation of ${}^{197}{Au}$ by relativistic heavy ions

S. B. Kaufman, E. P. Steinberg, B. D. Wilkins, and D. J. Henderson

Phys. Rev. C 22, 1897 (1980) - Published 1 November, 1980

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The cross sections and recoil properties of a number of target fragmentation products formed by the reactions of 4.8- and 25-GeV ${}^{12}C$ and 7.6-GeV ${}^{20}{Ne}$ with ${}^{197}{Au}$ have been measured. Comparisons between these data for relativistic heavy ions and those for relativistic protons have been used to test the hypotheses of factorization and limiting fragmentation. The cross sections for most of the nuclides measured are related for different projectiles by the ratio of the total reaction cross sections. An exception is the light nuclides ( $A < 30$ ), for which enhanced yields are found for heavy-ion projectiles compared to protons. The velocities imparted to recoil fragments by the projectiles are considerably larger for the heavy ions of $\sim 0.4 A$ GeV than for protons, but are the same for $2.1 A$ GeV ${}^{12}C$ (25-GeV kinetic energy) and 28-GeV protons. Limiting fragmentation has not been reached at energies of $0.4 A$ GeV, as shown by the large change in recoil properties with increasing energy. The projectile kinetic energy appears to be more significant as a scaling variable than the velocity for relativistic heavy ions.

NUCLEAR REACTIONS ${}^{197}{Au} ({}^{12}C, X)$ , ( ${}^{20}{Ne}$ , $X$ ), $X = {}^{24}{Na} - {}^{196}{Au}$ , $E_{{}^{12}C} = 4.8 and 25$ GeV, $E_{{}^{20}{Ne}} = 7.6$ GeV; measured cross sections and recoil properties; deduced mean kinetic parameters; test of factorization and limiting fragmentation.

Influence of nuclear-trajectory variations on atomic-excitation probabilities

Berndt Müller and Volker Oberacker

Phys. Rev. C 22, 1909 (1980) - Published 1 November, 1980

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Slight variations in the relative motion of two colliding atoms on the excitation amplitudes of the electronic states are discussed. A new theoretical method is proposed which leads to a simple calculation of the electronic amplitudes for a modified classical trajectory $\bar{R} (t)$ provided the exact solution is known for one particular time dependence $R (t)$ . This is of considerable importance for practical calculations. The method is applied to deeply inelastic collisions between very heavy atoms and may be utilized also for muonic states during muon-induced fission.

NUCLEAR REACTIONS Heavy ions; influence of nuclear trajectory on atomic excitations.

Resonant behavior of the ${}^{24}{Mg}$ ( ${}^{16}O$ , ${}^{12}C$ ) ${}^{28}{Si}$ * ( $6.4 \leq E_{x} \leq 10$ MeV) reaction

S. J. Sanders, C. Olmer, D. F. Geesaman, W. Henning, D. G. Kovar, M. Paul, and J. P. Schiffer

Phys. Rev. C 22, 1914 (1980) - Published 1 November, 1980

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Excitation functions have been measured for the ${}^{24}{Mg}$ ( ${}^{16}O$ , ${}^{12}C$ ) ${}^{28}{Si}$ reaction populating states in ${}^{28}{Si}$ with $6.4 \leq E_{x} \leq 10$ MeV over the energy range $24 \leq E_{c . m .} \leq 36$ MeV. At each incident beam energy, cross sections were measured at three angles over the range $17 ° \leq θ_{c . m .} \leq 21 °$ . More complete angular distributions with $10 ° \leq θ_{c . m .} \leq 50 °$ were measured at $E_{c . m .} = 30.5 and 32.6$ MeV. Resonance-like structures are observed in the excitation functions and strongly correlate with those seen previously at forward angles for the ${}^{24}{Mg}$ ( ${}^{16}O$ , ${}^{12}C$ ) ${}^{28}{Si}$ (g.s.) transition. Estimates are made for the partial decay widths of the resonance at $E_{c . m .} = 30.8$ MeV to the excited states in ${}^{28}{Si}$ . Using different background assumptions, between 5% and 40% of the total width of this resonance can be atrributed to ${}^{12}C$ + ${}^{28}{Si}$ * ( $E_{x} < 10$ MeV) decays.

NUCLEAR REACTIONS ${}^{24}{Mg}$ ( ${}^{16}O$ , ${}^{12}C$ ) ${}^{28}{Si}$ * ( $6.4 <~ E_{x} <~ 10$ MeV); $24 <~ E_{c . m .} <~ 36$ MeV; measured $σ (E, θ)$ ; DWBA analysis; deduced partial widths.

Effect of the nuclear compressibility coefficient on the expansion of compressed nuclear matter

Arnold J. Sierk and J. Rayford Nix

Phys. Rev. C 22, 1920 (1980) - Published 1 November, 1980

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On the basis of a conventional nonrelativistic fluid-dynamics model, we study the expansion of spherically symmetric nuclear matter that is initially compressed and excited in head-on collisions of equal targets and projectiles at a laboratory bombarding energy per nucleon of 250 MeV. We use a new functional form for the nuclear equation of state which has the property that the speed of sound approaches the speed of light in the limit of infinite compression. For various values of the nuclear compressibility coefficient, the fluid-dynamical equations of motion are solved until the matter expands to a freezeout density at which fluid dynamics ceases to be valid. At this point the remaining thermal energy is superimposed in terms of a Maxwell-Boltzmann distribution with appropriate nuclear temperature. For nonzero values of the compressibility coefficient ranging form 100 to 400 MeV, the energy distribution at the freezeout density of the expanding matter depends slightly upon the compressibility coefficient. However, the final-energy distribution after thermal folding is independent of the compressibility coefficient to within graphical accuracy. For zero compressibility coefficient, which corresponds to the expansion of a perfect gas, the energy distribution is significantly different form that for nonzero compressibility coefficient at the freezeout point, and is slightly different from that for nonzero compressibility coefficient after thermal folding. For both zero and nonzero values of the compressibility coefficient, the final energy distributions are significantly different from a Maxwell-Boltzmann distribution corresponding to entirely thermal energy, and are moderately different from the energy distribution corresponding to the Siemens-Rasmussen approximation.

NUCLEAR REACTIONS Equal target and projectile, $\frac{E_{bom}}{nucleon} = 250$ MeV; calculated energy distribution of expanding spherically symmetric nuclear matter. High-energy heavy-ion collisions, nonrelativistic nuclear fluid dynamics, nuclear equation of state, nuclear freezeout, thermal folding with Maxwell-Boltzmann distribution, Siemens-Rasmussen approximation.

Correlated fission fragments emitted in the reaction of ${}^{16}O$ on ${}^{238}U$ at 20 MeV/nucleon

B. B. Back, K. L. Wolf, A. C. Mignerey, C. K. Gelbke, T. C. Awes, H. Breuer, V. E. Viola, Jr., and P. Dyer

Phys. Rev. C 22, 1927 (1980) - Published 1 November, 1980

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The reactions induced by 315-MeV ${}^{16}O$ ions on ${}^{238}U$ have been studied by observing the folding angle between the two fission fragments resulting from the sequential fission decay of the target residue in coincidence with reaction products ranging from protons to ${}^{16}O$ ions. A kinematical analysis shows that the emission of light particles ( $p$ , $d$ , $t$ , $α$ ) plays an important role for both central and peripheral reactions. It is concluded that these particles, most likely, are emitted during the early stages of the reaction.

NUCLEAR REACTIONS, FISSION ${}^{238}U ({}^{16}O, X f)$ , $X = p, d, t, \dots$ , $O$ , $E = 315$ MeV; measured $σ (E_{x})$ and fission fragment folding angle distributions. Deduced missing momentum and fission fragment mass distributions.

Alpha particle emission in peripheral heavy ion reactions at 20 MeV/u

M. Bini, C. K. Gelbke, D. K. Scott, T. J. M. Symons, P. Doll, D. L. Hendrie, J. L. Laville, J. Mahoney, M. C. Mermaz, C. Olmer, K. Van Bibber, and H. H. Wieman

Phys. Rev. C 22, 1945 (1980) - Published 1 November, 1980

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The reaction ${}^{197}{Au} ({}^{16}O, HI α)$ has been investigated at 310 MeV. The angular correlations of alpha particles measured in coincidence with projectile-like fragments are very strongly forward peaked; the reaction is dominated by large negative values of the three-body $Q$ value. Most of the observed alpha particles are emitted from projectile-like fragments. Within a factor of 2, no anisotropy of emission in the center-of-mass frame of the coincident projectile residue and alpha particle was found.

NUCLEAR REACTIONS ${}^{197}{Au} ({}^{16}O, HI α)$ , $E = 310$ MeV; measured two-dimensional HI- $α$ coincident energy and angular correlations; deduced reaction mechanisms.

Quasiparticle properties of the pion and heavy-ion collisions

Hans J. Pirner

Phys. Rev. C 22, 1962 (1980) - Published 1 November, 1980

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The quasiparticle spectrum of the pion in nuclear matter is discussed. It contains the three branches: spin-isospin sound, quasifree pion, and the $Δ$ -hole branch. It is demonstrated how the spin-isospin branch is related to the phenomena of pion condensation and precritical scattering. Experimental consequences are derived. An event-by-event analysis of the $n$ -particle momentum distribution allows one to measure the order parameter ${\vec{k}}_{π}$ of the condensate and the amount of pre-equilibrium to equilibrium cross section. The importance of the quasifree pion branch for subthreshold pion production is shown. The inclusive $π^{\pm}$ -production cross section at 0 degrees and a kinetic energy of 34 MeV is calculated for Ne + NaF at 100, 200, and 300 MeV/N.

NUCLEAR REACTIONS Heavy-ion collisions, pion in nuclear matter, pion condensation, precritical scattering, $n$ -particle momentum distribution, collective parameters, subthreshold pion production $Ne + NaF \to π^{+} + X$ at 100, 200, and 300 MeV/N.

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Cross sections for the reaction ${}^{16}O (γ, p_{0}) {}^{15}N$ at forward angles for $E_{γ} = 80$ MeV

Forward-angle proton spectra in the continuum from the ${}^{58}{Ni} (p, x p)$ reaction at 100 MeV

Hypervirial theorems and the Breit-type recoil correction for pionic atoms

Pion-nucleus charge exchange reactions at low energies

$E 2$ interference terms in the Coulomb excitations of the Os and Pt nuclei

${}^{2}H (α, p α) n$ reaction between 9.735 and 11.30 MeV

Widths of ${}^{11}B$ levels below 9.0 MeV

${}^{12}C (p, n) {}^{12}N$ reaction at 99 MeV

Giant multipole resonances from inelastic scattering of 152-MeV alpha particles

Phenomenological model for elastic and inelastic scattering of high energy $α$ particles from nuclei

Effects of deformation on neutron total cross sections of even- $A$ Nd and Sm isotopes

${}^{24}{Mg}$ ( ${}^{18}O$ , ${}^{16}O$ ) ${}^{26}{Mg}$ reaction at $E_{{}^{18}O} = 50$ MeV including scattering in entrance and exit channel

Monte Carlo calculation of high-energy heavy-ion interactions

Target fragmentation of ${}^{197}{Au}$ by relativistic heavy ions

Influence of nuclear-trajectory variations on atomic-excitation probabilities

Resonant behavior of the ${}^{24}{Mg}$ ( ${}^{16}O$ , ${}^{12}C$ ) ${}^{28}{Si}$ * ( $6.4 \leq E_{x} \leq 10$ MeV) reaction

Effect of the nuclear compressibility coefficient on the expansion of compressed nuclear matter

Correlated fission fragments emitted in the reaction of ${}^{16}O$ on ${}^{238}U$ at 20 MeV/nucleon

Alpha particle emission in peripheral heavy ion reactions at 20 MeV/u

Quasiparticle properties of the pion and heavy-ion collisions

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