Recent Articles

Measurement of pre- and post-fission neutron emission at moderate excitation energies

Z. Fraenkel, I. Mayk, J. P. Unik, A. J. Gorski, and W. D. Loveland

Phys. Rev. C 12, 1809 (1975) - Published 1 December, 1975

Show Abstract

Fission fragment mass-energy distributions and the coincident neutron velocity distributions have been measured at 0° and 90° with respect to the fragment direction. The fissioning systems studied were ${}^{209}{Bi}$ , ${}^{232}{Th}$ , ${}^{233}U$ , ${}^{238}U$ , and ${}^{239}{Pu}$ bombarded with 45 MeV $α$ particles and ${}^{226}{Ra}$ bombarded with 16 MeV protons. From the above measured quantities the number of pre-fission neutrons and the number of post-fission neutrons were obtained as a function of fragment mass and total fragment kinetic energy. The average number of pre-fission neutrons emitted is 2.9±0.9 for the ${}^{232}{Th}$ target, 3.3±1.5 for ${}^{233}U$ , 3.6±1.6 for ${}^{238}U$ , and 2.7±0.8 for ${}^{239}{Pu}$ . The average number of post-fission neutrons emitted by these systems is 4.4±0.3, 4.2±0.7, 4.6±0.7, and 5.1±0.3, respectively. (The values reported for pre-fission neutrons include also contributions from scission neutrons.) The number of pre-fission neutrons from the ${}^{226}{Ra}$ + 16 MeV proton system is 0.5±0.3. The number of post-fission neutrons is 3.6±0.4. The number of neutrons emitted from the ${}^{209}{Bi}$ +45 MeV $α$ particle system is 3.6±0.2. The number of post-fission neutrons as a function of fragment mass and total kinetic energy which were obtained by the direct neutron measurements of this work are lower and are more consistent with calculated total energy balances than the values obtained by the indirect method based on the simultaneous measurement of both the kinetic energy and the velocity of the fission fragments. Our results for the average number of pre-fission neutrons are compared with calculations based on the conventional expression for $\frac{Γ_{f}}{Γ_{n}}$ . The agreement between the calculated results and our experimental results is satisfactory. However, the calculations predict spallation cross sections which are much larger than those obtained experimentally by radiochemical methods.

NUCLEAR REACTIONS, FISSION ${}^{209}{Bi} (α, f)$ , ${}^{232}{Th} (α, x n f)$ , ${}^{233, 238}U (α, x n f)$ , ${}^{239}{Pu} (α, x n f)$ , $E = 45$ MeV; ${}^{226}{Ra} (p, x n f)$ , $E = 16$ MeV; measured coin. fragment energy, neutron velocity at $θ = 0 °, 90 °$ with respect to fragment; deduced number of pre-fission, post-fission neutrons.

Neutron hole states of ${}^{99}{Mo}$

P. K. Bindal, D. H. Youngblood, R. L. Kozub, and P. H. Hoffmann-Pinther

Phys. Rev. C 12, 1826 (1975) - Published 1 December, 1975

Show Abstract

The ( $p, d$ ) and ( $d, t$ ) reactions on ${}^{100}{Mo}$ have been used at bombarding energies of ∼ 40 MeV to populate neutron hole states of ${}^{99}{Mo}$ . Excitation energies and angular distributions were measured for levels up to 4.25 MeV in excitation. A distorted wave Born approximation analysis was used to make $l$ assignments and to obtain spectroscopic factors. Three distinct groups of weakly excited levels, one corresponding to $l = 4$ and two corresponding to $l = 1$ , were observed lying above 2.15 MeV excitation. A hole-core-coupling model is used to predict the properties of ${}^{99}{Mo}$ and fair agreement with the experiment is obtained.

NUCLEAR REACTIONS, NUCLEAR STRUCTURE ${}^{100}{Mo} (p, d)$ , ${}^{100}{Mo} (d, t)$ , $E ≃ 40$ MeV; measured $σ (θ)$ , ${}^{99}{Mo}$ levels, deduced $l$ , $S$ ; calculated $J$ , $π$ , $S$ , particle-core-coupling model.

Recoil properties of ${}^{232}{Th} (γ, x n)$ evaporation products

H. Jungclas, R. Brandt, and G. Stark

Phys. Rev. C 12, 1834 (1975) - Published 1 December, 1975

Show Abstract

Photonuclear recoil studies with thick Th $F_{4}$ targets and thick catcher foils for the emitted products after neutron evaporation were carried out with bremsstrahlung of a 55 MeV electron beam. The hypothetical range ( $R_{0}$ ) of the ${}^{232}{Th} (γ, x n) {}^{232 - x}{Th}$ reaction recoils ( $x = 5, 6$ ) in the target material was found to be about 12 μg/ ${cm}^{2}$ (in the frame of the moving compound nucleus). The effective ranges in beam and in the opposite direction ( $R_{+}$ and $R_{-}$ ) lead to forward-backward recoil ratios ( $\frac{R_{+}}{R_{-}}$ ) of 2-4, increasing with the number of evaporated neutrons ( $x = 4, 5, 6$ ). The reaction kinematics are discussed in the compound nucleus model, first by a step-by-step Monte Carlo calculation, then by a mean value analysis. The calculated mean ranges and forward-backward recoil ratios agree satisfactorily with the experimental results for most residual nuclei studied.

NUCLEAR REACTION ${}^{232}{Th} (γ, x n)$ , $E_{γ} \leq 55$ MeV measured ranges ( $x = 5, 6$ ) and forward-backward recoil ratios ( $x = 4, 5, 6$ ) compared with estimations based on compound nucleus model.

( $d, p$ ) reactions in the continuum

K. C. Chan, B. L. Cohen, L. Shabason, J. E. Alzona, and T. Congedo

Phys. Rev. C 12, 1844 (1975) - Published 1 December, 1975

Show Abstract

${}^{65}{Cu}$ , ${}^{116}{Cd} (d, p)$ reaction cross sections in the continuum regions have been measured for deuteron energies 9, 10.5, and 12 MeV. They are compared to a theoretical calculation in which the spectroscopic factors of usual ( $d, p$ ) reaction calculations for nuclear states are replaced by the strength distributions for different single neutron configurations. These distributions are Gaussian curves centered at single neutron orbits with widths proportional to their excitation energies. Good agreement is found for angular distributions and incident deuteron energy dependences, although the predicted absolute cross sections are about 50% higher than the measurements. Uncertainties in the calculations are discussed.

NUCLEAR REACTION ${}^{65}{Cu}$ , ${}^{116}{Cd} (d, p)$ , $E_{d} = 9 - 12$ MeV, continuum. Excitation energies 2-6 MeV, angular distribution. DWBA calculations compared.

Parameters of the subthreshold fission structure in ${}^{240}{Pu}$

George F. Auchampaugh and Lawrence W. Weston

Phys. Rev. C 12, 1850 (1975) - Published 1 December, 1975

Show Abstract

The neutron subthreshold fission cross section of ${}^{240}{Pu}$ has been measured from 500 to 10000 eV using the Oak Ridge electron linear accelerator neutron facility. A total of 82 fission widths were obtained from area and shape analysis of those resonances which define the class II states at ≅ 782, ≅ 1405, ≅ 1936, and ≅ 2700 eV. The average square of the coupling matrix element for the first three class II states is 1.85 ± 1.43 e $V^{2}$ [standard deviation (SD)]. The average class II fission width is 2.5 ± 1.0 eV (SD). Approximately 22 clusters of class I resonances were observed below 10 keV, which results in a value of 450 ± 50 eV for the average class II level spacing. Assuming parabolic inner and outer barriers, the following barrier parameters were obtained: $V_{A} - \frac{B_{n}}{ℏ ω_{A}} = {0.71}_{- 0.09}^{+ 0.21}$ and $V_{B} - \frac{B_{n}}{ℏ ω_{B}} = {0.53}_{- 0.06}^{+ 0.09}$ .

NUCLEAR REACTIONS ${}^{240}{Pu} (n, f)$ ; 500 to 10 000 eV; $Γ_{f λ^{'}}$ , $Γ_{f λ^{''}}^{II}$ , $〈 {H_{λ^{'} λ^{''}}}^{2} 〉$ .

High-spin states in ${}^{109}{Cd}$

M. Meyer, R. Béraud, J. Danière, R. Rougny, J. Rivier, J. Tréherne, and D. Barnéoud

Phys. Rev. C 12, 1858 (1975) - Published 1 December, 1975

Show Abstract

Levels of ${}^{109}{Cd}$ populated by ${}^{108}{Pd} (α, 3 n γ) {}^{109}{Gd}$ have been studied by measuring $γ$ -ray excitation functions, direct $γ$ spectra, $γ - γ$ coincidences, and $γ$ -ray angular distributions and by performing lifetime measurements. An intense $γ$ -ray cascade has been observed, built on the ${\frac{11}{2}}^{-}$ intrinsic state and involving states of spin ${\frac{11}{2}}^{-}$ , ${\frac{15}{2}}^{-}$ , ${\frac{19}{2}}^{-}$ , ${\frac{23}{2}}^{-}$ , and ( ${\frac{27}{2}}^{-}$ ). A decay level scheme is proposed including states up to 4502 keV.

NUCLEAR REACTION ${}^{108}{Pd} (α, 3 n γ)$ , $E = 36.7 - 45.8$ MeV; enriched ${}^{108}{Pd}$ target; measured $σ (E)$ , $γ - γ$ coin, $σ (θ) γ$ , $T_{\frac{1}{2}}$ , deduced decay scheme, $J$ , $π$ .

Magnetic moment of the $d_{\frac{3}{2}}$ hole state in ${}^{45}{Ti}$

B. Haas, A. Chevallier, J. Chevallier, C. Gehringer, J. C. Merdinger, N. Schulz, J. Styczen, P. Taras, M. Toulemonde, and J. P. Vivien

Phys. Rev. C 12, 1865 (1975) - Published 1 December, 1975

Show Abstract

The nuclear $g$ factor of the 330 keV $\frac{3}{2^{+}}$ state in ${}^{45}{Ti}$ has been measured as $g = 0.65 \pm 0.16$ using the ${}^{42}{Ca} (α, n) {}^{45}{Ti}$ reaction and the time-integral perturbed angular distribution method. The deduced magnetic moment value $μ = (0.98 \pm 0.24) μ_{N}$ is consistent with a $d_{\frac{3}{2}}$ neutron hole state interpretation of this level.

NUCLEAR REACTION ${}^{42}{Ca} (α, n)$ , $E = 9.0$ MeV; measured $γ (θ, H)$ . 330 keV ${}^{45}{Ti}$ level deduced $μ$ . Enriched target, Ge(Li) detectors.

Energy levels of ${}^{12}B$

F. Ajzenberg-Selove, R. Middleton, and J. D. Garrett

Phys. Rev. C 12, 1868 (1975) - Published 1 December, 1975

Show Abstract

The ${}^{9}{Be} ({}^{7}{Li}, α) {}^{12}B$ reaction has been studied at $E ({}^{7}{Li}) = 20$ MeV using a multiangle spectrograph. Thirty-seven states of ${}^{12}B$ with $E_{x} < 14$ MeV have been observed. Angular distributions are presented for the first seven states of ${}^{12}B$ . The neutron reduced widths extracted from experimental total widths of the positive parity states are compared with shell-model predictions.

NUCLEAR REACTIONS ${}^{9}{Be} ({}^{7}{Li}, α)$ , $E = 20$ MeV; measured $σ (θ)$ . $Γ$ , ${}^{12}B$ deduced levels.

Hyperfine interactions of light nuclei recoil-implanted into iron

E. Bożek, A. Z. Hrynkiewicz, J. C. Merdinger, and J. P. Vivien

Phys. Rev. C 12, 1873 (1975) - Published 1 December, 1975

Show Abstract

The perturbed integral angular distribution technique has been used to study hyperfine interactions of light nuclei recoil-implanted into iron. Heavy-ion-induced fusion-evaporation reactions populated the excited states of ${}^{37}{Ar}$ , ${}^{39, 40, 41}K$ , and ${}^{41}{Ca}$ , whose deexciting $γ$ rays were observed in a Ge(Li) detector. In all cases the measured shifts of the angular distributions were found much smaller than the ones calculated using the known values of $g$ factors, lifetimes, and strengths of the internal hyperfine fields. This can be explained under the assumption that only a fraction of the nuclei feel the full internal magnetic field, while the rest of them do not feel any magnetic interaction at all. Different fractions obtained for ${}^{40}K$ and ${}^{41}K$ suggest a migration process on a ns time scale of the implanted ions in the lattice.

NUCLEAR REACTIONS ${}^{28}{Si} ({}^{14}N, x n, y p) {}^{37}{Ar}$ , ${}^{39}K$ , ${}^{40}K$ ; ${}^{27}{Al} ({}^{16}O, x n, y p) {}^{41}K$ , ${}^{41}{Ca}$ ; $E = 30 - 35$ MeV. Measured $I_{γ} (θ, H)$ . Deduced $H_{hyp}$ at Ar(Fe), K(Fe), Ca(Fe).

${}^{10}B ({}^{14}N, α) {}^{20}{Ne}$ reaction in the region of the Coulomb barrier

J. L'Ecuyer, R. Volders, C. Cardinal, L. Deschênes, and N. Marquardt

Phys. Rev. C 12, 1878 (1975) - Published 1 December, 1975

Show Abstract

The differential cross sections for the reaction ${}^{10}B ({}^{14}N, α) {}^{20}{Ne}$ leading to the lower excited states of ${}^{20}{Ne}$ were measured at ${}^{14}N$ energies of 25 and 35 MeV. The excitation functions of those states were also measured at 0, 30, and 110° over the range $5.2 \leq E_{c . m .} < 13$ MeV. The data were analyzed in terms of the statistical compound nucleus model. The average behavior of this reaction is fairly reproduced by these calculations with reasonable values of the level density and spin cutoff parameters for this excitation energy region. Some features, however, could not be explained by this model. In particular, a large structure was seen in the 0° excitation function at 10 MeV(c.m.) in many channels, which is clearly not of statistical origin. A possible explanation is the presence of a doorway state in ${}^{24}{Mg}$ at the corresponding excitation energy.

NUCLEAR REACTIONS ${}^{10}B ({}^{14}N, α) {}^{20}{Ne}$ , $E = 13 - 35$ MeV; measured $σ (θ)$ at $E = 25, 35$ MeV and $σ (E)$ at $θ_{lab} = 0, 30, 110 °$ . Enriched targets; Hauser-Feshbach and correlation analysis; deduced resonance energy and width.

Abrasion-ablation in reactions between relativistic heavy ions

J. Hüfner, K. Schäfer, and B. Schürmann

Phys. Rev. C 12, 1888 (1975) - Published 1 December, 1975

Show Abstract

The abrasion-ablation model for reactions between relativistic heavy ions is derived from Glauber's multiple scattering theory. Simple expressions are found for the abrasion cross section and for the excitation energy of the projectile after abrasion. Both quantities depend on nuclear densities and on the nucleon-nucleon forward scattering amplitude. They do not contain any adjustable parameters. With a very simple model for the ablation process, fragmentation cross sections for the production of individual isotopes are calculated. The agreement with experiment is good for most cases. Systematic discrepancies are observed and are analyzed in terms of an extension of the abrasion-ablation model.

NUCLEAR REACTIONS Relativistic heavy ions, calculated fragmentation cross sections.

Low-lying states in ${}^{20}{Ne}$ populated by the ${}^{19}F$ ( ${}^{7}{Li}$ , ${}^{6}{He}$ ) ${}^{20}{Ne}$ reaction at 34 MeV

M. E. Williams-Norton, G. M. Hudson, K. W. Kemper, G. E. Moore, G. A. Norton, R. J. Puigh, and A. F. Zeller

Phys. Rev. C 12, 1899 (1975) - Published 1 December, 1975

Show Abstract

Angular distributions have been measured for transitions to ${}^{20}{Ne}$ states up to 7.43 MeV in excitation populated in the ${}^{19}F$ ( ${}^{7}{Li}$ , ${}^{6}{He}$ ) ${}^{20}{Ne}$ reaction at $E_{{}^{7}{Li}} = 34$ MeV. Elastic scattering of ${}^{6}{Li}$ and ${}^{7}{Li}$ at 34 MeV from ${}^{19}F$ was also performed and optical model parameters were determined from fits to the measured angular distributions. These optical model parameters were used in finite-range distorted-width Born-approximation analyses of the single nucleon transfer data to extract spectroscopic factors for states at 0.0, 1.634, 4.247, 5.785, 6.722, and 7.424 MeV excitation in ${}^{20}{Ne}$ . Spectroscopic factors obtained from this reaction agree well with those from light-ion transfer reactions. However, the $2 s_{\frac{1}{2}}$ calculation for the ${}^{20}{Ne}$ ground state is out of phase with the data by 7°. The " $j$ -forbidden" $4^{+}$ state at 4.247 MeV excitation is found to be weakly excited in the ${}^{19}F$ ( ${}^{7}{Li}$ , ${}^{6}{He}$ ) ${}^{20}{Ne}$ reaction.

NUCLEAR REACTIONS ${}^{19}F$ ( ${}^{6}{Li}$ , ${}^{6}{Li}$ ), ( ${}^{7}{Li}$ , ${}^{7}{Li}$ ), ( ${}^{7}{Li}$ , ${}^{6}{He}$ ), $E = 34 and 37$ MeV; measured $σ (θ)$ ; deduced optical model parameters, deduced $S$ for ${}^{20}{Ne}$ . Natural targets, finite range DWBA analysis, resolution 150 keV, $θ = 1 - 50 °$ , $Δ θ = 2 - 2.5 °$ .

Experimental studies of the resonance at $E_{c . m .} = 19.7$ MeV in the ${}^{12}C$ + ${}^{16}O$ system

D. Shapira, R. G. Stokstad, M. W. Sachs, A. Gobbi, and D. A. Bromley

Phys. Rev. C 12, 1907 (1975) - Published 1 December, 1975

Show Abstract

A resonance appearing in the ${}^{12}C$ + ${}^{16}O$ system at a center-of-mass incident energy of 19.7 MeV has been studied experimentally. Excitation functions for the ${}^{12}C$ + ${}^{16}O$ inelastic scattering and the ${}^{12}C ({}^{16}O, α) {}^{24}{Mg}^{*}$ and ${}^{12}C ({}^{16}O, p) {}^{27}{Al}^{*}$ reaction channels were measured. The width of the resonance was shown to be more than double the average level width in ${}^{28}{Si}$ at excitation energies around 36.5 MeV where this resonance appears. The resonance is enhanced at large angles in the elastic and inelastic channels and it is found to be equally strong at $θ_{c . m .} = 3 ° and 177 °$ for the ${}^{12}C ({}^{16}O, p) {}^{27}{Al}$ reaction. The yield of 6.13 MeV $γ$ radiation has been measured and is observed to resonate at $E_{c . m .} = 19.7$ MeV. High resolution measurements of the particle yield at $E_{c . m .} = 19.7$ MeV, $θ_{lab} = 7.5 °$ for the reaction ${}^{12}C$ ( ${}^{16}O$ , ${}^{12}C$ ) ${}^{16}O$ * (6.05, 6.13 MeV) show that the $3^{-}$ (6.13 MeV) state is populated much more strongly than the $0^{+}$ (6.05 MeV) state. These results do not support the suggestion that the resonance has a ${}^{12}C$ - $α$ - ${}^{12}C$ molecular structure. Measurements of inelastic scattering at higher energies suggest the existence of additional correlated structures. A statistical analysis of the $α$ -particle yields indicates that both compound and direct mechanisms contribute to the reaction. A discussion of the properties of the resonance in terms of intermediate structure and the statistical theory of Moldauer is given.

NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{16}O$ , ${}^{12}C$ ) ${}^{16}O$ *, ${}^{12}C ({}^{16}O, α) {}^{24}{Mg}$ , and ${}^{12}C ({}^{16}O, p) {}^{27}{Al}$ $18 \leq E_{c . m .} \leq 21$ MeV, $θ_{c . m .} = 3 °, 177 °$ . Resonance in ${}^{28}{Si}$ at 36.5 MeV excitation energy. Decay channels studied. Measured $γ$ ray excitation functions [NaI(Tl)] and charged particle yield with magnetic spectrograph. Fluctuation and Hauser-Feshbach analysis of ${}^{12}C ({}^{16}O, α) {}^{24}{Mg}^{*}$ data.

Analysis of the ${}^{12}C ({}^{6}{Li}, α) {}^{14}N$ reaction for $E ({}^{6}{Li}) = 33$ MeV

R. L. White, L. A. Charlton, and K. W. Kemper

Phys. Rev. C 12, 1918 (1975) - Published 1 December, 1975

Show Abstract

The ${}^{12}C ({}^{6}{Li}, α) {}^{14}N$ reaction to the first eight $T = 0$ states was studied at $E ({}^{6}{Li}) = 33$ MeV in the angular range $12.5 ° \leq θ \leq 165 °$ . The measurements for the positive parity states in ${}^{14}N$ also included the angular range from 2.5°-12.5°. Calculations for the angular distributions were done within the framework of the distorted-wave Born approximation (DWBA) with three different prescriptions: (1) zero-range two-particle transfer, (2) finite-range deuteron-cluster transfer, and (3) finite-range two-particle transfer, which included a full microscopic description of the two nucleon wave function. None of the three types of DWBA calculations could reproduce the data. Consequently, the possibility of multistep contributions was investigated by computing the spectroscopic amplitudes for transitions from the $2^{+}$ first excited state in ${}^{12}C$ to the first two states in ${}^{14}N$ . It was found that the transfer strengths from the ${}^{12}C$ (4.43 MeV) to the ${}^{14}N$ (0.00 MeV) and ${}^{14}N$ (3.95 MeV) $J^{π} = 1^{+}$ levels are larger than those from the ${}^{12}C$ ground state. These results coupled with previous results showing that the ${}^{12}C ({}^{6}{Li}, α) {}^{14}N$ reaction is not compound at this energy imply that multistep mechanisms may be very important.

NUCLEAR REACTIONS ${}^{12}C ({}^{6}{Li}, α)$ ; $E = 33$ MeV; measured $σ (θ)$ , $θ_{lab} = 2.5 ° - 165 °$ ; compared with zero range and finite range DWBA.

Lifetimes of rotational states in ${}^{232}{Th}$

Noah R. Johnson, R. J. Sturm, E. Eichler, M. W. Guidry, G. D. O'Kelley, R. O. Sayer, D. C. Hensley, N. C. Singhal, and J. H. Hamilton

Phys. Rev. C 12, 1927 (1975) - Published 1 December, 1975

Show Abstract

Lifetimes of the $4^{+}$ through $10^{+}$ members of the ground-state rotational band in ${}^{232}{Th}$ have been measured by the Doppler-shift recoil-distance technique. These states were Coulomb excited by 152-MeV ${}^{40}{Ar}$ ions, and measurements were carried out in coincidence with the backscattered projectiles. The half-lives for the $4^{+}$ through $10^{+}$ states are 164 ± 13, 66.2 ± 5.1, 25.1 ± 2.3, and 11.2 ± 1.7 ps, respectively. The $B (E 2)$ values deduced for these states are systematically about 10% smaller than rigid-rotor values; however, the constancy of the transition quadrupole moments is interpreted as an indication of rotational behavior.

NUCLEAR REACTIONS ${}^{232}{Th} ({}^{40}{Ar}, {}^{40}{Ar}^{'}, γ)$ , $E = 152$ MeV; measured life-times $4^{+}$ , $6^{+}$ , $8^{+}$ , and $10^{+}$ members g.s. band ${}^{232}{Th}$ ; deduced $B (E 2)$ values, compared with theory.

Sign of the $E 4$ moment in ${}^{236}U$ by multiple Coulomb excitation with ${}^{40}{Ar}$ ions

M. W. Guidry, E. Eichler, N. R. Johnson, G. D. O'Kelley, R. J. Sturm, and R. O. Sayer

Phys. Rev. C 12, 1937 (1975) - Published 1 December, 1975

Show Abstract

Multiple Coulomb excitation with ${}^{40}{Ar}$ projectiles has been used to excite the ground state rotational band of ${}^{236}U$ through the $12^{+}$ state. A comparison of the experimental and theoretical excitation probabilities confirms a positive value for the $E 4$ moment, removing the sign ambiguity inherent in the determination of this moment by $alpha$ -particle Coulomb excitation.

NUCLEAR REACTIONS Multiple Coulomb excitation, ${}^{40}{Ar}$ + ${}^{236}U$ , $E_{lab} = 145.8, 152.4$ MeV; measured excitation probabilities, compared to theoretical predictions; deduced sign of $E 4$ moment.

Inelastic scattering of heavy ions

K. E. Rehm, H. J. Körner, M. Richter, H. P. Rother, J. P. Schiffer, and H. Spieler

Phys. Rev. C 12, 1945 (1975) - Published 1 December, 1975

Show Abstract

Angular distributions and excitation functions for elastic and inelastic scattering have been measured with ${}^{16}O$ , ${}^{18}O$ , and ${}^{32}S$ projectiles on Ca, Ni, Mo, and Sn isotopes. The experimental data show oscillations in the angular distributions which are more pronounced for projectile excitations than for target excitations. These oscillations are discussed within the semiclassical model. The experimental results have been analyzed with the modified distorted-wave Born-approximation (DWBA) code dwuck. The theoretical predictions using conventional (macroscopic form factor) DWBA calculations fail to describe the data accurately; a modification of the form factor is required to achieve a satisfactory description.

NUCLEAR REACTIONS ${}^{58, 60, 62, 64}{Ni}$ ( ${}^{18}O$ , ${}^{18}O$ ), ( ${}^{18}O$ , ${}^{18}O$ '), ( ${}^{18}O$ , ${}^{18}O$ *), $E = 63$ MeV; ${}^{60}{Ni}$ ( ${}^{16}O$ , ${}^{16}O$ ), ( ${}^{16}O$ , ${}^{16}O$ '), $E = 61.4$ MeV; ${}^{92}{Mo}$ ( ${}^{18}O$ , ${}^{18}O$ ), ( ${}^{18}O$ , ${}^{18}O$ '), ( ${}^{18}O$ , ${}^{18}O$ *), $E = 72$ MeV; ${}^{92}{Mo}$ ( ${}^{16}O$ , ${}^{16}O$ ), ( ${}^{16}O$ , ${}^{16}O$ '), $E = 70.7$ MeV; ${}^{120}{Sn}$ ( ${}^{18}O$ , ${}^{18}O$ ), ( ${}^{18}O$ , ${}^{18}O$ '), ( ${}^{18}O$ , ${}^{18}O$ *), $E = 72$ MeV; ${}^{122}{Sn}$ ( ${}^{16}O$ , ${}^{16}O$ ), ( ${}^{16}O$ , ${}^{16}O$ '), $E = 73.95$ MeV; ${}^{40}{Ca}$ ( ${}^{32}S$ , ${}^{32}S$ ), ( ${}^{32}S$ , ${}^{32}S$ *), $E = 100$ MeV; $θ \approx 20 - 60 °$ , $Δ θ = 1 ° or 2 °$ . ${}^{60}{Ni}$ ( ${}^{18}O$ , ${}^{18}O$ ), ( ${}^{18}O$ , ${}^{18}O$ '), ( ${}^{18}O$ , ${}^{18}O$ *). Measured $σ (E)$ , $E = 30 - 44$ MeV, $Δ E = 1 - 2$ MeV, $θ = 175 °$ ; ${}^{92}{Mo}$ -( ${}^{18}O$ , ${}^{18}O$ ), ( ${}^{18}O$ , ${}^{18}O$ '), ( ${}^{18}O$ , ${}^{18}O$ *). Measured $σ (E)$ , $E = 40 - 56$ MeV, $Δ E = 1 - 2$ MeV, $θ = 178 °$ . ( ${}^{18}O$ * denotes inelastic excitation of the projectile.) Optical-model, DWBA, and semiclassical analysis.

Implications of high energy pion-nucleon scattering data for pion-nucleus scattering

D. J. Ernst and Gerald A. Miller

Phys. Rev. C 12, 1962 (1975) - Published 1 December, 1975

Show Abstract

Energy-dependent separable potentials are generated by solving the inverse problem for three sets of pion-nucleon phase shifts which differ only at very high ( $E_{c . m .} > 1900$ MeV) energies. While the off-shell $t$ matrices thus generated have substantial differences, these effects are small for $π$ -nucleus cross sections as calculated within the impulse approximation.

NUCLEAR REACTIONS $π$ -nucleus elastic scattering, impulse approximation; $π$ -nucleon off-shell models.

$T$ asymmetry in the strong interaction at medium energies

R. A. Bryan

Phys. Rev. C 12, 1968 (1975) - Published 1 December, 1975

Show Abstract

We examine current intermediate-energy nucleon-nucleon data sensitive to $T$ asymmetry and conclude that of these data, some $np$ polarization and asymmetry measurements give the best evidence that $T$ is good, despite the fact that these data have the largest errors of any of the data considered. This conclusion is reached using a one-boson-exchange potential due to Bryan and Gersten, wherein $T$ is violated at short distances. We argue that any short-range $T$ -asymmetric model would probably lead to the same conclusion. We show that the current $N - N$ data admit the possibility of strong-interaction $T$ asymmetry, so long as it be of short range. For experimentalists who may search for strong-interaction $T$ violation in intermediate energy $N - N$ scattering, we suggest maximum errors for several measurements so that any such $T$ violation may not be missed.

NUCLEAR REACTIONS $E = 145, 500, 600, 635$ MeV, $P_{A} - P_{B}$ , $P - G$ null measurements ranked according to a time-reversal-asymmetric one-boson-exchange model.

Proton-induced ${}^{3}{He}$ breakup at 156 MeV

J. P. Didelez, R. Frascaria, N. Fujiwara, I. D. Goldman, E. Hourany, H. Nakamura-Yokota, F. Reide, and T. Yuasa

Phys. Rev. C 12, 1974 (1975) - Published 1 December, 1975

Show Abstract

The ${}^{3}{He}$ breakup induced by a 156 MeV proton beam was studied using a liquid target and the adequate kinematic conditions for $p - p$ , $p - n$ , and $p - d$ quasifree scattering or three nucleon final state interactions. The ( $p, 2 p$ ) and ( $p, pn$ ) differential cross section spectra ( $d^{3} σ$ ) are similar to each other for recoil energy less than 10 MeV and coincide to those calculated with the plane-wave impulse approximation. The $d^{3} σ$ spectrum of the ( $p, pd$ ) reaction shows a peak at the minimum $p - d$ relative energy indicating their final state interaction.

NUCLEAR REACTIONS ${(\frac{d^{3} σ}{d Ω_{1} d Ω_{2} d E_{1}})}_{e x p, P W I A}$ for ${}^{3}{He} (p, d p)$ , ( $p, 2 p$ ), and ( $p, pn$ ) at 156 MeV. Studies of $p - p$ , $p - n$ , and $p - d$ quasifree interactions. The $p - d$ final state interaction observed.

Select page:

Physical Review C

Recent Articles

Filter

Recent Issues

Measurement of pre- and post-fission neutron emission at moderate excitation energies

Neutron hole states of ${}^{99}{Mo}$

Recoil properties of ${}^{232}{Th} (γ, x n)$ evaporation products

( $d, p$ ) reactions in the continuum

Parameters of the subthreshold fission structure in ${}^{240}{Pu}$

High-spin states in ${}^{109}{Cd}$

Magnetic moment of the $d_{\frac{3}{2}}$ hole state in ${}^{45}{Ti}$

Energy levels of ${}^{12}B$

Hyperfine interactions of light nuclei recoil-implanted into iron

${}^{10}B ({}^{14}N, α) {}^{20}{Ne}$ reaction in the region of the Coulomb barrier

Abrasion-ablation in reactions between relativistic heavy ions

Low-lying states in ${}^{20}{Ne}$ populated by the ${}^{19}F$ ( ${}^{7}{Li}$ , ${}^{6}{He}$ ) ${}^{20}{Ne}$ reaction at 34 MeV

Experimental studies of the resonance at $E_{c . m .} = 19.7$ MeV in the ${}^{12}C$ + ${}^{16}O$ system

Analysis of the ${}^{12}C ({}^{6}{Li}, α) {}^{14}N$ reaction for $E ({}^{6}{Li}) = 33$ MeV

Lifetimes of rotational states in ${}^{232}{Th}$

Sign of the $E 4$ moment in ${}^{236}U$ by multiple Coulomb excitation with ${}^{40}{Ar}$ ions

Inelastic scattering of heavy ions

Implications of high energy pion-nucleon scattering data for pion-nucleus scattering

$T$ asymmetry in the strong interaction at medium energies

Proton-induced ${}^{3}{He}$ breakup at 156 MeV

Filter

Recent Issues

Filter

Article Lookup

Enter a citation