Recent Articles

${}^{34}S$ by the ${}^{32}S (t, p) {}^{34}S$ reaction

D. J. Crozier, H. T. Fortune, R. Middleton, and S. Hinds

Phys. Rev. C 17, 455 (1978) - Published 1 February, 1978

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The ${}^{32}S (t, p) {}^{34}S$ reaction was studied at a bombarding energy of $E_{t} = 10$ MeV. The outgoing protons were analyzed in a multiangle magnetic spectrograph. Levels in ${}^{34}S$ below $E_{x} = 8.50$ MeV were identified and angular distributions were extracted for 30 groups. These angular distributions were analyzed using distorted-wave techniques. Results are compared to recent shell-model calculations.

[NUCLEAR REACTIONS ${}^{32}S (t, p)$ , $E = 10$ MeV; measured $σ (E_{p}, θ)$ . Deduced ${}^{34}S$ levels, $J$ , $π$ , configurations. DWBA analysis.]

Neutron-proton polarization at 50 MeV

J. L. Romero, M. W. McNaughton, F. P. Brady, N. S. P. King, T. S. Subramanian, and J. L. Ullmann

Phys. Rev. C 17, 468 (1978) - Published 1 February, 1978

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Data are presented for the polarization parameter $P (θ)$ in $n - p$ scattering at 50.0 MeV. The results confirm the overall trend of previous data and are in good agreement with phase shift predictions.

[NUCLEAR REACTIONS ${}^{1}H (\vec{n}, p) n$ , $E = 50.0$ MeV; measured $P (θ)$ for $69.3 \leq θ_{c . m .}$ ≤149.6, about every 10° c.m.]

Theory of ( $p, 2 p$ ) reactions at medium energies

P. C. Wright, R. G. Storer, and I. E. McCarthy

Phys. Rev. C 17, 473 (1978) - Published 1 February, 1978

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A new and effective means of calculating matrix elements relevant to direct interactions is introduced and applied to a distorted-wave $t$ matrix approximation analysis of the ${}^{12}C (p, 2 p) {}^{11}B$ and ${}^{16}O (p, 2 p) {}^{15}N$ reactions at 45-50 MeV incident energy. A realistic separable two-body $t$ matrix has been employed and core polarization, whereby the final state is generated after excitation of giant resonance target states, has been included. The integrals involved in the matrix elements were calculated analytically by making a parametrization of the distorted scattering wave functions, the nucleon-nucleon interaction, and the bound state wave function, the parameters being chosen in accordance with elastic ( $p, p$ ) and inelastic ( $p, p^{'}$ ) data and realistic shell model wave functions. The results indicate the inadequacy of a distorted-wave $t$ -matrix approximation analysis at these energies.

[NUCLEAR REACTIONS ${}^{12}C (p, 2 p)$ , $E = 50$ MeV; ${}^{16}O (p, 2 p)$ , $E = 45$ MeV; DWTA analysis, including resonance effects.]

Isospin conservation in the reactions ${}^{16}O (p, t) {}^{14}O (g . s .)$ and ${}^{16}O (p, {}^{3}{He}) {}^{14}N (2.31 MeV)$

C. D. Goodman, D. L. Hanson, D. C. Hensley, and R. G. Stokstad

Phys. Rev. C 17, 493 (1978) - Published 1 February, 1978

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Differential cross section measurements are given for the isospin related reaction channels ${}^{16}O (p, t) {}^{14}O (g . s .)$ and ${}^{16}O (p, {}^{3}{He}) {}^{14}N (2.31 MeV)$ for several proton energies near 29 MeV. The isospin mixture of the exit channel changes significantly with small changes in bombarding energy. Distorted-wave Born-approximation calculations reproduce the changes reasonably well. Calculations show, however, that compound nuclear contributions might be large.

[NUCLEAR REACTIONS ${}^{16}O (p, t)$ , $(p, {}^{3}{He}) E = 27 - 30.7$ MeV; measured $σ (E; θ)$ ; DWBA analysis; Hauser-Feshbach calculations.]

${}^{188, 190, 192}{Os} (t, p)$ reaction at 15 MeV

E. R. Flynn and D. G. Burke

Phys. Rev. C 17, 501 (1978) - Published 1 February, 1978

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A study of the heavier osmium isotopes ${}^{190}{Os}$ , ${}^{192}{Os}$ , and ${}^{194}{Os}$ has been made with the ( $t, p$ ) reaction using a 15 MeV triton beam. The osmium nuclei may be considered as transitional nuclei going from a deformed to a spherical shape with increasing neutron number and the ( $t, p$ ) reaction is used to probe this change. The study principally investigates the position and strength of the $0^{+}$ states, a number of new such states being observed. The nucleus ${}^{194}{Os}$ is also reported in some detail for the first time with 15 excited levels observed and 7 spin assignments made.

[NUCLEAR REACTIONS ${}^{188, 190, 192}{Os} (t, p)$ , $E_{t} = 15$ MeV. Measured $σ (θ)$ ; enriched targets; DWBA calculations deduced $J$ , $π$ .]

Charged-particle—producing reactions of 15-MeV neutrons on ${}^{51}V$ and ${}^{93}{Nb}$

S. M. Grimes, R. C. Haight, and J. D. Anderson

Phys. Rev. C 17, 508 (1978) - Published 1 February, 1978

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Cross sections for the ( $n, x p$ ), ( $n, d$ ), and ( $n, x α$ ) reactions for 15-MeV neutrons on ${}^{51}V$ and ${}^{93}{Nb}$ have been measured with a magnetic quadrupole spectrometer. The importance of the ( $n, n^{'} p$ ) reaction as a source of protons is examined by comparing these results with those recently obtained for ${}^{46}{Ti}$ . Good fits to the ( $n, x p$ ) and ( $n, x α$ ) energy spectra require contributions from both equilibrium and nonequilibrium reactions, while only the latter appear in the ( $n, d$ ) spectra. Calculated values for the ( $n, n^{'} p$ ) and ( $n, n^{'} α$ ) cross sections agree well with the experimental values. The cross sections are ${}^{51}V (n, x p)$ 91 ± 14 mb, ${}^{51}V (n, x d)$ 7 ± 3 mb, ${}^{51}V (n, x α)$ 17 ± 3 mb, ${}^{93}{Nb} (n, x p)$ 51 ± 8 mb, ${}^{93}{Nb} (n, x d)$ 8 ± 3 mb, and ${}^{93}{Nb} (n, x α)$ 14 ± 3 mb.

[NUCLEAR REACTIONS ${}^{51}V (n, x p)$ , ${}^{51}V (n, x d)$ , ${}^{51}V (n, x α)$ , ${}^{93}{Nb} (n, x p)$ , ${}^{93}{Nb} (n, x d)$ , ${}^{93}{Nb} (n, x α)$ , $E_{n} = 14.8$ MeV, measured $σ (E_{p}, θ)$ , $σ (E_{d}, θ)$ , $σ (E_{α}, θ)$ , Hauser-Fesh-bach analysis; deduced reaction mechanism.]

Evidence for the first 9/ $2^{+}$ state in ${}^{75}{Br}$ and maximum deformation at $N \sim 42$

M. Behar, A. Filevich, G. García Bermúdez, and M. A. J. Mariscotti

Phys. Rev. C 17, 516 (1978) - Published 1 February, 1978

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Evidence for the first 9/ $2^{+}$ state in ${}^{75}{Br}$ at 694 keV has been obtained through the ${}^{75}{As}$ (55 MeV $α, 4 n$ ) reaction. This result shows a sharp change in the systematics of the 9/ $2^{+}$ states in the Br isotopes and implies that the maximum of prolate deformation is reached for $N \sim 42$ . The previously postulated correlation between 9/ $2^{+}$ and $2^{+}$ states in the neighboring even-even nuclei is confirmed by the present experiment.

[NUCLEAR REACTION ${}^{75}{As} (α, 4 n γ)$ , $E = 30 to 55$ MeV; measured $σ (E, E_{γ}, θ)$ , $γ - γ$ coin. ${}^{75}{Br}$ deduced levels, $J$ , $π$ , $T_{\frac{1}{2}}$ . Ge(Li) detector.]

Neutron capture cross section of ${}^{159}{Tb}$ from 2.6 to 700 keV

M. Mizumoto, R. L. Macklin, and J. Halperin

Phys. Rev. C 17, 522 (1978) - Published 1 February, 1978

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The ${}^{159}{Tb} (n, γ)$ cross section was measured using a neutron time of flight facility. The average capture cross section was deduced from 2.6 to 700 keV and in combination with recently reported transmission results, was well fitted with energy independent strength functions. Resonance parameters for many of the observed peaks from 2.6 to 3.4 keV were determined by a nonlinear least squares fitting program. The $γ$ -ray multiplicity for average capture was measured, giving the relatively low value, 2.45 ± 0.01 at 4 keV, implying a high proportion of two-step cascades. The fluctuations in the cross section about that computed from strength functions were analyzed. No significant nonrandom structure in the cross section was indicated.

[NUCLEAR REACTIONS ${}^{159}{Tb} (n, γ)$ , $E = 2.6 - 700$ keV; measured $σ (E)$ , ${\bar{E}}_{γ} (E)$ ; deduced ${}^{160}{Tb}$ resonance parameters, average $γ$ -ray multiplicities, average level spacing, $S_{1}$ , $S_{2}$ strength functions, $s$ -wave inelastic competition to the ${\frac{5}{2}}^{+}$ 58 keV level of ${}^{159}{Tb}$ .]

Nuclear levels in ${}^{191, 193, 195, 197}{Pt}$ excited via neutron pickup

G. Berrier-Ronsin, M. Vergnes, G. Rotbard, J. Vernotte, J. Kalifa, R. Seltz, and H. L. Sharma

Phys. Rev. C 17, 529 (1978) - Published 1 February, 1978

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The ( $p, d$ ) reaction has been performed at 26 MeV incident energy on targets of ${}^{196}{Pt}$ (97.5%), ${}^{194}{Pt}$ (97.4%), and ${}^{192}{Pt}$ (57%) and natural Pt. The deuterons were detected in the focal plane of the split pole magnetic spectrometer with a resolution of 16 to 20 keV full width at half maximum. In ${}^{193}{Pt}$ , 32 levels, 23 of which are observed for the first time, are populated below 1250 keV; in ${}^{195}{Pt}$ , 24 levels are observed below 1200 keV; in ${}^{191}{Pt}$ , due to low enrichment and target uniformity problems, only 7 levels are clearly separated. Comparison of the measured angular distributions with distorted-wave Born-approximation calculations allows parity assignments and spin limits for most of the final levels. Spectroscopic factors are deduced. A cursory investigation of the ( $d, t$ ) reaction on the same targets with about 10 keV resolution has permitted us to separate several clustered low lying levels and to identify and study, using a ${}^{198}{Pt}$ target, a few levels of ${}^{197}{Pt}$ .

[NUCLEAR REACTIONS ${}^{198, 196, 194, 192}{(p, d)} (d, t) {}^{197, 195, 193, 191}{Pt}$ , $E = 26$ MeV; measured $σ (θ)$ ; ${}^{197}{Pt}$ , ${}^{195}{Pt}$ , ${}^{193}{Pt}$ , ${}^{191}{Pt}$ levels deduced, $J$ , $π$ , $C {}^{2}S$ . Natural and separated targets.]

Microscopic calculation of the form factors for deeply inelastic heavy-ion collisions within the statistical model

B. R. Barrett, S. Shlomo, and H. A. Weidenmüller

Phys. Rev. C 17, 544 (1978) - Published 1 February, 1978

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Agassi, Ko, and Weidenmüller have recently developed a transport theory of deeply inelastic heavy-ion collisions based on a random-matrix model. In this work it was assumed that the reduced form factors, which couple the relative motion with the intrinsic excitation of either fragment, represent a Gaussian stochastic process with zero mean and a second moment characterized by a few parameters. In the present paper, we give a justification of the statistical assumptions of Agassi, Ko, and Weidenmüller and of the form of the second moment assumed in their work, and calculate the input parameters of their model for two cases: ${}^{40}{Ar}$ on ${}^{208}{Pb}$ and ${}^{40}{Ar}$ on ${}^{120}{Sn}$ . We find values for the strength, correlation length, and angular momentum dependence of the second moment, which are consistent with those estimated by Agassi, Ko, and Weidenmüller. We consider only inelastic excitations (no nucleon transfer) caused by the penetration of the single-particle potential well of the light ion into the mass distribution of the heavy one. This is combined with a random-matrix model for the high-lying excited states of the heavy ion. As a result we find formulas which relate simply to those of Agassi, Ko, and Weidenmüller, and which can be evaluated numerically, yielding the results mentioned above. Our results also indicate for which distances of closest approach the Agassi-Ko-Weidenmüller theory breaks down.

[NUCLEAR REACTIONS Random-matrix model and shell model used to calculate distribution of form factors.]

Surface transparent potentials and a coupled-channel Born-approximation study of diffractive behavior in heavy-ion induced reactions

A. J. Baltz and S. Kahana

Phys. Rev. C 17, 555 (1978) - Published 1 February, 1978

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Coupled channel explanations, which have been offered for the diffractive behavior observed in the differential ground state-ground state cross sections of ( ${}^{16}O$ , ${}^{18}O$ ) reactions on Ni isotopes, are in apparent disagreement with data for transfer to the ${}^{18}O$ ( $2^{+}$ ) state. A study of available quasielastic reaction data, elastic, inelastic, and transfer suggests the surface-transparent potentials both can better describe the optical phenomena observed in the angular shapes and can minimize effects due to coupled channels. As a byproduct a description, which does not require a large ${}^{18}O$ ( $2_{1}^{+}$ ) quadrupole moment, is obtained for the troublesome angular distribution in ${}^{18}O$ + ${}^{58}{Ni}$ inelastic scattering.

[NUCLEAR REACTIONS CCBA analysis ( ${}^{16}O$ , ${}^{18}O$ ) reaction on Ni isotopes and all related quasielastic processes. Dependence on optical potentials examined.]

Levels in ${}^{23}{Na}$ populated by the ${}^{12}C ({}^{15}N, α)$ reaction

S. T. Thornton, D. E. Gustafson, K. R. Cordell, L. C. Dennis, T. C. Schweizer, and J. L. C. Ford, Jr.

Phys. Rev. C 17, 576 (1978) - Published 1 February, 1978

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Forty-nine angular distributions for states in ${}^{23}{Na}$ up to 16.6 MeV in excitation energy populated by the ${}^{12}C ({}^{15}N, α) {}^{23}{Na}$ reaction have been measured in 400 keV intervals for bombarding energies from 36.0 to 39.2 MeV. Hauser-Feshbach calculations have been made to suggest spins for most of the states observed. Shell-model predictions were used to guide the suggestions for positive-parity spin state locations. High-spin members of three rotational bands, $K^{π} = \frac{3}{2^{+}}, \frac{1}{2^{+}}, and \frac{1}{2^{-}}$ , were suggested and average moment-of-inertia parameters were extracted from the band systematics.

[NUCLEAR REACTIONS ${}^{12}C ({}^{15}N, α)$ , $E_{{}^{15}N} = 36.0 to 39.2$ MeV, measured $σ (E)$ for $θ_{lab} = 7^{\circ}$ ; $E_{{}^{15}N} = 36.4, 37.2, 38.0, 38.8$ MeV, measured $σ (θ)$ ; ${}^{23}{Na}$ deduced levels, classification into rotational bands. Hauser-Feshbach calculations, suggested $J$ values, moment of inertia calculations. Natural target.]

${}^{10}B$ -induced $2 n$ and $2 p$ transfer reactions on light targets

M. Hamm and K. Nagatani

Phys. Rev. C 17, 586 (1978) - Published 1 February, 1978

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A systematic study is made of 100 MeV ${}^{10}B$ -induced $2 n$ and $2 p$ transfer reactions on light targets of ${}^{12}C$ , ${}^{14}N$ , and ${}^{16}O$ . These reactions are seen to selectively populate only a few states in the residual nuclei, showing them to be useful for studying states of particular structures. Known states with ${(p_{\frac{1}{2}} d_{\frac{5}{2}})}_{3}$ - and ${(d_{\frac{5}{2}})}^{2}_{4^{+}}$ structures are strongly populated in the $T = 1$ mass-14 nuclei. The known ${(d_{\frac{5}{2}})}^{2}_{4^{+}}$ states in the $T = 1$ mass-18 nuclei are also strongly populated. The lowest $2^{+}$ states (also of a $d_{\frac{5}{2}}^{2}$ nature) in these latter nuclei are populated more weakly. Exact finite-range distorted-wave Born-approximation calculations, assuming a cluster transfer of the two neutrons or protons, are presented for the strongly populated levels in the mass-14 and -18 residual nuclei, and for the $2^{+}$ level in ${}^{18}O$ . With the exception of this $2^{+}$ state and the unbound $4^{+}$ state in ${}^{14}O$ , the shapes of the angular distributions are well fitted by the cluster approximation. The distorted-wave Born-approximation normalizations to the data are compared to cluster spectroscopic factors calculated from shell model wave functions for the various states involved. In most cases, the extracted factors agree with the calculated spectroscopic factors to within a factor of 3. This agreement suggests that the reaction mechanism is predominantly a one-step transfer of a $T = 1$ , $S = 0$ pair of neutrons or protons. The known structures of the strongly populated states in the mass-14 and -18 nuclei can be used to interpret newly observed states in the mass-16 spectra, in which there are two groups of strongly populated levels in each nucleus. The doublet in the low excitation region corresponds to the known $2^{-}$ and $3^{-}$ states presumably populated through the transfer of the nucleon pair into a ${(p_{\frac{1}{2}} d_{\frac{5}{2}})}_{3}$ - configuration coupled to the ${}^{14}N_{1 +}$ target core. The higher group of states is predicted to arise from the transfer of the nucleon pair into a ${(d_{\frac{5}{2}})}^{2}_{4^{+}}$ configuration coupled to the $1^{+}$ core. The results of a Bansal-French-Zamick weak coupling model calculation for the center of gravity of the triplet of states from this ${(d_{\frac{5}{2}})}^{2}_{4^{+}}$ configuration in the $T = 1$ mass-16 nuclei are presented. These are seen to be in agreement with the observed energies of the high excitation peaks in the data.

[NUCLEAR REACTIONS ${}^{12}C$ , ${}^{14}N$ , ${}^{16}O$ ( ${}^{10}B$ , ${}^{8}{Li}$ ), $E = 100$ MeV; ${}^{12}C$ , ${}^{14}N$ , ${}^{16}O$ ( ${}^{10}B$ , ${}^{8}B$ ), $E = 100$ MeV; measured $σ (θ)$ ; DWBA analysis; extracted and calculated $2 n$ and $2 p$ spectroscopic factors; weak coupling model predictions.]

Gamma-ray linear polarization measurements in ${}^{129}{Ba}$

J. Gizon, A. Gizon, Y. K. Lee, and D. O. Elliott

Phys. Rev. C 17, 596 (1978) - Published 1 February, 1978

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The linear polarization of $γ$ rays in ${}^{129}{Ba}$ produced by the reaction ${}^{120}{Sn} ({}^{12}C, 3 n)$ was measured using a Compton polarimeter made of two Ge(Li) coaxial detectors. The results establish unambiguously the $h_{\frac{11}{2}}$ band structure and its separation into the $\tilde{Ω} = j = \frac{11}{2}$ and $\tilde{Ω} = j - 1 = \frac{9}{2}$ level subsystems. The existence of the $g_{\frac{7}{2}}$ band is shown for the first time in the mass region $A \approx 130$ .

[NUCLEAR REACTIONS ${}^{120}{Sn} ({}^{12}C, 3 n)$ , $E = 52$ MeV; measured linear polarization of $γ$ rays; deduced spins and parities of levels and multipole mixing ratios of transitions in ${}^{129}{Ba}$ ; triaxial shape.]

Angular-momentum effects in pre-equilibrium processes

D. G. Sarantites, L. Westerberg, R. A. Dayras, M. L. Halbert, D. C. Hensley, and J. H. Barker

Phys. Rev. C 17, 601 (1978) - Published 1 February, 1978

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Cross sections and the first three moments of the $γ$ -ray multiplicity distribution were measured for many transitions corresponding to $xn$ and $xn α$ products from bombardments of ${}^{166}{Er}$ with ${}^{4}{He}$ , ${}^{150}{Nd}$ with ${}^{20}{Ne}$ , and ${}^{130}{Te}$ with ${}^{40}{Ar}$ . The ${}^{4}{He}$ and ${}^{20}{Ne}$ bombarding energies were chosen to produce ${}^{170}{Yb}$ compound nuclei at similar excitation energies, approximately 63, 77, and 92 MeV. A Ge(Li)-NaI anti-Compton spectrometer was used in coincidence with nine 5.1-cm by 7.6-cm NaI(Tl) detectors. For the reactions ( ${}^{20}{Ne}, x n$ ) and ( ${}^{40}{Ar}, x n$ ), the average $γ$ -ray multiplicity ${〈 M 〉}_{x}$ increases linearly with decreasing $x$ as expected from the statistical decay of compound nuclei. In the ( ${}^{4}{He}, x n$ ) reactions, ${〈 M 〉}_{x}$ is similar for large $x$ but for small $x$ it decreases substantially with decreasing $x$ . The latter corresponds to a shift in the population toward the low $J$ values of levels in ${}^{170 - x}{Yb}$ prior to $γ$ decay. Also, in the few-neutron channels the average multiplicity associated with a given gating transition in the residual nucleus is much smaller for transitions between low-lying levels. These features, absent in the heavy-ion bombardments, indicate a strong contribution from pre-equilibrium neutron emission. The measured ( ${}^{4}{He}, x n$ ) cross sections are in reasonable agreement with those calculated from the geometry-dependent hybrid model of pre-equilibrium emission except for the smallest values of $x$ ; the latter results and the low ${〈 M 〉}_{x}$ values for $x \leq 4$ suggest that more than one pre-equilibrium neutron is emitted in these channels.

[NUCLEAR REACTIONS ${}^{150}{Nd} ({}^{20}{Ne}, x n γ)$ , ( ${}^{20}{Ne}, x n α γ$ ), $x = 4 - 8$ , $E = 94.2, 110.7$ MeV; ${}^{130}{Te} ({}^{40}{Ar}, x n γ)$ , $x = 3 - 5$ , $E = 154.5$ MeV; ${}^{166}{Er} ({}^{4}{He}, x n γ)$ , ( ${}^{4}{He}, x n α γ$ ), $x = 2 - 8$ , $E = 67.6 - 95.3$ MeV; measured $σ (E, E γ)$ , $γ$ -ray multiplicities; deduced $J$ distributions in evaporation residues. Enriched target, anti-Compton Ge(Li)-NaI spectrometer.]

Lifetime measurements and multiple Coulomb excitation in ${}^{162}{Dy}$

Ph. Hubert, Noah R. Johnson, and E. Eichler

Phys. Rev. C 17, 622 (1978) - Published 1 February, 1978

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Rotational states up to spin $12^{+}$ in ${}^{162}{Dy}$ have been Coulomb excited by 148.6 MeV ${}^{40}{Ar}^{8 +}$ ions. The half-lives of the $4^{+}$ , $6^{+}$ , and $8^{+}$ states were measured by the Doppler-shift recoil-distance method and were found to be 132±6, 18.4±1.0, and 4.6±0.3 ps, respectively. In addition, relative Coulomb excitation probabilities up through the $12^{+}$ member in the ground-state band were measured. All $B (E 2)$ values are in good agreement with rotational model expectations except for the $10^{+}$ state, and within $2 σ$ it is in agreement.

[NUCLEAR REACTIONS ${}^{162}{Dy} ({}^{40}{Ar}, {}^{40}{Ar}^{'} γ)$ , $E = 148.6$ MeV; measured half-lives of $4^{+}$ , $6^{+}$ , and $8^{+}$ states and Coulomb excitation probabilities up through the $12^{+}$ level; deduced $B (E 2)$ values, compared with theory.]

Reorientation effect measurements in ${}^{122}{Te}$ and ${}^{128}{Te}$

M. J. Bechara, O. Dietzsch, M. Samuel, and U. Smilansky

Phys. Rev. C 17, 628 (1978) - Published 1 February, 1978

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Measurements of the Coulomb excitation probabilities of the first $2^{+}$ state of ${}^{122}{Te}$ and ${}^{128}{Te}$ were carried out using back-scattered ions of ${}^{4}{He}$ , ${}^{14}N$ , ${}^{16}O$ , and ${}^{18}O$ . Quadrupole moments $Q_{2^{+}}$ and reduced transition probabilities $B (E 2; 0^{+} \to 2^{+})$ were determined. The $Q_{2^{+}}$ deduced for the positive sign of the $2_{2}^{+}$ interference term are $- 0.57 \pm 0.05 e$ b and $- 0.06 \pm 0.05 e$ b for ${}^{122}{Te}$ and ${}^{128}{Te}$ , respectively.

[NUCLEAR REACTIONS ${}^{122, 128}{Te} (α, α^{'})$ , $E_{α} = 8 - 10$ MeV; ${}^{122, 128}{Te}$ ( ${}^{14}N$ , ${}^{14}N$ '), $E_{14_{N}} = 32 - 37$ MeV; ${}^{122, 128}{Te}$ ( ${}^{16}O$ , ${}^{16}O$ '), $E_{16_{O}} = 30.5 - 42$ MeV; ${}^{122}{Te}$ ( ${}^{18}O$ , ${}^{18}O$ '), $E_{18_{O}} = 34 - 35$ MeV; measured $σ (E_{α}, E_{α^{'}})$ , $σ (E_{14_{N}}, E_{14_{N^{'}}})$ , $σ (E_{16_{O}}, E_{16_{O^{'}}})$ , $σ (E_{18_{O}}, E_{18_{O^{'}}})$ . ${}^{122, 128}{Te}$ deduced $Q_{2^{+}}$ , $B (E 2, 0^{+} \to 2^{+})$ . Enriched targets.]

Lifetimes of ground-band states in ${}^{150}{Nd}$

S. W. Yates, Noah R. Johnson, L. L. Riedinger, and A. C. Kahler

Phys. Rev. C 17, 634 (1978) - Published 1 February, 1978

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Members of the ground-state band of ${}^{150}{Nd}$ to spin $8^{+}$ have been Coulomb excited with 149-MeV ${}^{40}{Ar}$ ions, and the lifetimes of these states have been measured by the Doppler-shift recoil distance method. The half-lives of the $2^{+}$ , $4^{+}$ , $6^{+}$ , and $8^{+}$ states are 1.44±0.07 ns, 63.0±3.2 ps, 12.4±1.1 ps, and 4.0±0.4 ps, respectively. The observed enhancement of the experimental $B (E 2)$ 's over rotational values is found to be in agreement with a simple band-mixing description.

[NUCLEAR REACTIONS ${}^{150}{Nd} ({}^{40}{Ar}, {}^{40}{Ar}^{'} γ)$ , $E = 149$ MeV; measured lifetimes of $2^{+}$ , $4^{+}$ , $6^{+}$ , and $8^{+}$ ground-band states, recoil distance method; deduced $B (E 2)$ values, compared with theory.]

Coulomb-nuclear interference in the inelastic projectile excitation of ${}^{20}{Ne}$ by ${}^{40}{Ca}$

Nguyen Van Sen, G. Ratel, R. Darves-Blanc, J. C. Gondrand, and F. Merchez

Phys. Rev. C 17, 639 (1978) - Published 1 February, 1978

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Coulomb-nuclear interference effects were investigated in the inelastic scattering of ${}^{20}{Ne}$ by ${}^{40}{Ca}$ with excitation of the first $2^{+}$ state in ${}^{20}{Ne}$ . Measurements were performed at 54 and 60.5 MeV for the elastic and inelastic angular distributions and from 36 to 95 MeV for the excitation functions. The elastic data were analyzed in terms of the optical model. The inelastic results were compared with distorted-wave Born-approximation and coupled channel calculations. The reorientation effect was investigated.

[NUCLEAR REACTIONS ${}^{40}{Ca}$ ( ${}^{20}{Ne}$ , ${}^{20}{Ne}$ ); $E = 54, 60.5$ MeV measured $σ (θ)$ ; $E = 36 - 95$ MeV, measured $σ (θ, E)$ , $θ = 20, 28, 36, 44, 52^{\circ}$ ; for g.s., first $2^{+}$ in ${}^{20}{Ne}$ . Optical model and DWBA analysis. Coupled-channel calculations with reorientation effects. Natural target.]

Modified one-body nuclear dissipation

Arnold J. Sierk, Steven E. Koonin, and J. Rayford Nix

Phys. Rev. C 17, 646 (1978) - Published 1 February, 1978

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We study a modification of the one-body dissipation mechanism for the conversion of energy of collective nuclear motion into internal single-particle excitation energy. One-body nuclear dissipation is a consequence of the long mean free path of nucleons inside a nucleus, and arises from nucleons colliding with the moving boundary of the nucleus rather than with other individual nucleons. In our modification, which attempts to incorporate self-consistency, the dissipation rate is proportional to an integral over the nuclear surface of the square of the normal component of the normal derivative of the velocity. The resulting properties of this dissipation are qualitatively similar to those of ordinary two-body viscosity rather than to those of the original one-body dissipation. In particular, for small oscillations about a sphere the dissipation rate increases with increasing multipole degree, and in fission this dissipation leads to more elongated scission shapes and to decreased fission-fragment kinetic energies. By adjusting the parameter that specifies the magnitude of this dissipation, we are able to reproduce adequately the experimental most probable fission-fragment kinetic energies for the fission of nuclei throughout the Periodic Table.

[NUCLEAR REACTIONS, FISSION Calculated dependence of fission-fragment kinetic energies upon modified one-body dissipation. Dynamics of large-scale nuclear collective motion, nuclear dissipation, hydrodynamical model, Werner-Wheeler method.]

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${}^{34}S$ by the ${}^{32}S (t, p) {}^{34}S$ reaction

Neutron-proton polarization at 50 MeV

Theory of ( $p, 2 p$ ) reactions at medium energies

Isospin conservation in the reactions ${}^{16}O (p, t) {}^{14}O (g . s .)$ and ${}^{16}O (p, {}^{3}{He}) {}^{14}N (2.31 MeV)$

${}^{188, 190, 192}{Os} (t, p)$ reaction at 15 MeV

Charged-particle—producing reactions of 15-MeV neutrons on ${}^{51}V$ and ${}^{93}{Nb}$

Evidence for the first 9/ $2^{+}$ state in ${}^{75}{Br}$ and maximum deformation at $N \sim 42$

Neutron capture cross section of ${}^{159}{Tb}$ from 2.6 to 700 keV

Nuclear levels in ${}^{191, 193, 195, 197}{Pt}$ excited via neutron pickup

Microscopic calculation of the form factors for deeply inelastic heavy-ion collisions within the statistical model

Surface transparent potentials and a coupled-channel Born-approximation study of diffractive behavior in heavy-ion induced reactions

Levels in ${}^{23}{Na}$ populated by the ${}^{12}C ({}^{15}N, α)$ reaction

${}^{10}B$ -induced $2 n$ and $2 p$ transfer reactions on light targets

Gamma-ray linear polarization measurements in ${}^{129}{Ba}$

Angular-momentum effects in pre-equilibrium processes

Lifetime measurements and multiple Coulomb excitation in ${}^{162}{Dy}$

Reorientation effect measurements in ${}^{122}{Te}$ and ${}^{128}{Te}$

Lifetimes of ground-band states in ${}^{150}{Nd}$

Coulomb-nuclear interference in the inelastic projectile excitation of ${}^{20}{Ne}$ by ${}^{40}{Ca}$

Modified one-body nuclear dissipation

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