Recent Articles

Separable expansions to local potentials in a quasipotential approach

Francisco Luciano Viana and Sadhan K. Adhikari

Phys. Rev. C 19, 1655 (1979) - Published 1 April, 1979

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A recently proposed method which was successfully used to make separable expansions for the nonrelativistic two-body $t$ matrix is here used to construct separable expansions for the two-body $t$ matrix satisfying relativistic unitarity in a quasipotential approach. The present method, unlike other commonly used methods, does not require the calculations of eigenfunctions and eigenvalues of the kernel of the scattering equations and yields simple form factors. The method is illustrated for a simple nucleon-nucleon potential in the context of the Blankenbecler-Sugar equation.

NUCLEAR REACTIONS Finite rank approximations to the $t$ matrix of a local potential, relativistic unitarity, Blankenbecler-Sugar equation solved, phase shift calculated.

$R$ -matrix method for nuclear reaction theory

C. Chandler and W. Tobocman

Phys. Rev. C 19, 1660 (1979) - Published 1 April, 1979

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The $R$ -matrix method has been used by Tobocman as a basis for deriving the equations of $N$ -body scattering theory. It is claimed that this method avoids some of the ambiguities inherent in the more conventional approaches. We point out and correct some errors in Tobocman's treatment. We also give arguments to support the contention that our correction terms make a negligible contribution to the final equations.

NUCLEAR REACTIONS Errors in Tobocman's $R$ -matrix method formulation of $N$ -body scattering theory are pointed out and corrected; correction terms appear to be negligible.

Photonuclear cross sections for ${}^{18}O$

J. G. Woodworth, K. G. McNeill, J. W. Jury, R. A. Alvarez, B. L. Berman, D. D. Faul, and P. Meyer

Phys. Rev. C 19, 1667 (1979) - Published 1 April, 1979

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All the major photonuclear cross sections for ${}^{18}O$ , including $σ (γ, p)$ , $σ [(γ, n) + (γ, n p)]$ , and $σ (γ, 2 n)$ , were measured as a function of photon energy from threshold to 42 MeV. The photon energy resolution was between 200 and 300 keV. The source of radiation was the monoenergetic photon beam obtained from the annihilation in flight of fast positrons. The partial photoneutron cross sections were determined by neutron multiplicity counting, and the average neutron energies for both single- and double-photoneutron events were determined simultaneously with the cross-section data by the ring-ratio technique. The photoproton cross section was determined by counting the delayed neutrons from the $β$ -decay of the residual ${}^{17}N$ nuclei. Integrated cross sections were extracted from the data and compared with sum-rule predictions. Resonances in the pygmy-resonance region exhibit substantial decay branching to negative-parity states in ${}^{17}O$ . Significant differences in the branching of resonances in the giant-resonance region to the various partial cross sections, together with the photoneutron-energy data, allow isospin assignments to be made for all the resonances, with the consequent delineation of the isospin strength distribution for ${}^{18}O$ . Evidence was found for two weak but broad resonances above the giant-resonance region. Finally, comparison with the corresponding cross sections for ${}^{16}O$ shows considerable differences between the two nuclei.

NUCLEAR REACTIONS ${}^{18}O$ ( $γ$ , $n$ ), $E_{γ} = 8.0 - 41.8$ MeV; measured $4 π$ prompt, delayed neutron yield for monoenergetic photons; $σ (E_{γ}, 1 n)$ , $σ (E_{γ}, 2 n)$ , $σ (E_{γ}, p)$ , integrated cross sections; detailed distribution of isospin strength; comparison with ${}^{16}O$ .

Photoneutron cross sections for ${}^{13}C$

J. W. Jury, B. L. Berman, D. D. Faul, P. Meyer, K. G. McNeill, and J. G. Woodworth

Phys. Rev. C 19, 1684 (1979) - Published 1 April, 1979

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The photoneutron cross sections for ${}^{13}C$ have been measured from near threshold to over 40 MeV using monoenergetic photons from positron in-flight annihilation. Several sharp features below the giant resonance were distinguished. The results both for this "pygmy-resonance" region and for the giant resonance near 24 MeV differ markedly from previously reported measurements and provide a much better quantitative comparison with recent theoretical calculations of the photoneutron reaction in ${}^{13}C$ . Comparison of the measured total photoneutron cross section with recent data on the ground-state photoreaction and with average photoneutron energies provides evidence for the isospin splitting of the giant resonance for this nucleus.

NUCLEAR REACTIONS: ${}^{13}C$ ( $γ$ , $n$ ), $E_{γ} = 7.6 - 41.8$ MeV; measured $4 π$ neutron yield for monoenergetic photons; $σ (E_{γ}, 1 n)$ , $σ (E_{γ}, 2 n)$ , integrated cross sections, isospin splitting of the giant resonance.

Interaction current effects in proton-neutron bremsstrahlung

M. A. Preston and W. van Dijk

Phys. Rev. C 19, 1693 (1979) - Published 1 April, 1979

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A phenomenological interaction current density is used to investigate the effect on non-minimal coupling on $np$ bremsstrahlung when the $np$ interaction is nonlocal. The interaction current density depends upon a parameter which varies so that in one limit minimal coupling obtains and for other values of the parameter non-minimal couplings due to exchanges of charged particles of various masses are simulated. It is shown that for small photon energies minimal coupling is a good approximation. At higher energies, the effect on the matrix element is studied for several nucleon interactions. We find that the electric current part of the cross section may vary by as much as 10% depending on the type of coupling used. This result has implications in considering the extent to which bremsstrahlung experiments can discriminate between different $N - N$ interaction models.

NUCLEAR REACTIONS $p - n$ bremsstrahlung; dependence on structure of interaction currents; calculation matrix elements.

Structure in the giant resonance region of ${}^{16}O$ observed with the reaction ${}^{13}C$ ( ${}^{3}{He}$ , $γ$ ) ${}^{16}O$

E. Ventura, J. R. Calarco, C. C. Chang, E. M. Diener, D. G. Mavis, S. S. Hanna, and G. A. Fisher

Phys. Rev. C 19, 1705 (1979) - Published 1 April, 1979

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The capture reaction ${}^{13}C$ ( ${}^{3}{He}$ , $γ$ ) ${}^{16}O$ has been studied over an excitation energy range of 25 to 30 MeV in ${}^{16}O$ . The 90° differential yield curve for the ground state transition shows resonances at $E_{x} = 25.1, 26.0 and 27.3$ MeV. The measured angular distributions are consistent with a spin and parity assignment of $J^{π} = 1$ — to these states. The relation between this structure and that observed in the ${}^{15}N$ ( $p$ , $γ_{0}$ ) ${}^{16}O$ reaction is discussed. The 90° differential yield curves for the doublet transitions $γ_{1} + γ_{2}$ and $γ_{3} + γ_{4}$ were also measured. The former shows resonances at $E_{x} = 26.0, 26.6, 27.2, 27.7, and 28.6$ MeV, while the latter shows a broad resonance centered at $E_{x} ≃ 27.5$ MeV with mild structure. Both curves suggest the existence of giant resonance strength built on the excited states of ${}^{16}O$ .

NUCLEAR REACTIONS ${}^{13}C$ ( ${}^{3}{He}$ , $γ$ ) ${}^{16}O$ , ${}^{E}3_{He}$ = 3.0-8.5 MeV, measured $σ (E_{{}^{3}{He}}, E_{γ}, θ)$ . ${}^{16}O$ deduced resonances and structure in giant resonance region. Enriched ${}^{13}C$ target.

Four-body model of the four-nucleon system

A. C. Fonseca

Phys. Rev. C 19, 1711 (1979) - Published 1 April, 1979

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Using a nonrelativistic field theoretic formalism a soluble model of the four-nucleon system is developed and solved numerically. Two- and three-body scattering proceeds through intermediate quasiparticles and the resulting $T$ matrices are separable in momentum space and satisfy two- and three-body unitarity. The 2 + 2 subamplitudes are treated exactly by the convolution method. The resulting four-body equations reduce to single variable integral equations following partial wave decomposition and can be solved numerically by rotation of contour together with matrix inversion. A complete phase shift calculation is performed for the isospin triplet interaction. The differential cross sections for all two-to-two processes initiated by $p$ + ${}^{3}{He}$ , $n$ + ${}^{3}H$ and $d + d$ are compared with experiment for energies up to 25 MeV in the center of mass. Total elastic and reaction cross sections for the processes initiated by $n$ + ${}^{3}H$ are also calculated and compared with experimental data.

NUCLEAR REACTIONS Four-body calculation of ${}^{3}H$ ( $n$ , $n$ ) ${}^{3}H$ , ${}^{3}{He}$ ( $p$ , $p$ ) ${}^{3}{He}$ , ${}^{2}H$ ( $d$ , $d$ ) ${}^{2}H$ , ${}^{2}H$ ( $d$ , $n$ ) ${}^{3}{He}$

Method for scattering equations

Sadhan K. Adhikari

Phys. Rev. C 19, 1729 (1979) - Published 1 April, 1979

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A method is proposed for calculating fully off-shell $t$ matrix elements which are solutions of Lippmann-Schwinger-type equations. This is a generalization of the Kowalski version of the Sasakawa theory of scattering. The method relies on the Fredholm reduction of an integral equation whose kernel has a singularity at a fixed point. The method yields a $t$ matrix which satisfies the conditions of on-shell unitarity and can be readily generalized to the case of multichannel scattering problems.

NUCLEAR REACTIONS: Singular scattering equations, off-shell $t$ -matrix elements, multichannel scattering theory.

${}^{72}{Ge}$ from the ${}^{70}{Ge}$ ( $t$ , $p$ ) reaction

S. Mordechai, H. T. Fortune, R. Middleton, and G. Stephans

Phys. Rev. C 19, 1733 (1979) - Published 1 April, 1979

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The reaction ${}^{70}{Ge}$ ( $t$ , $p$ ) ${}^{72}{Ge}$ has been investigated with a 15-MeV triton beam. 30 levels of ${}^{72}{Ge}$ were observed up to about 4-MeV excitation, four of which were unreported previously. Angular distributions were measured and compared with distorted-wave Born-approximation calculations. Several new $0^{+}$ states have been observed in ${}^{72}{Ge}$ , one of which, at 1.709 MeV, is a new state and is the third $0^{+}$ level in ${}^{72}{Ge}$ . Many additional spin and parity assignments have been made. The ${}^{72}{Ge}$ nucleus shows a pattern of $0^{+}$ states that is considerable different from that of other even Ge isotopes. But for higher spins and both parities, ${}^{72}{Ge}$ is very similar to other even Ge nuclei.

NUCLEAR REACTIONS ${}^{70}{Ge}$ ( $t$ , $p$ ), $E_{t} = 15.0$ MeV; measured $σ (E_{p}, θ) {}^{72}{Ge}$ deduced levels, $L$ , $π$ , $J$ . DWBA analysis.

Levels in ${}^{78, 80, 82}{As}$ from the ${}^{78, 80, 82}{Se}$ ( $t$ , ${}^{3}{He}$ ) reactions

F. Ajzenberg-Selove, E. R. Flynn, D. L. Hanson, and S. Orbesen

Phys. Rev. C 19, 1742 (1979) - Published 1 April, 1979

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Levels of the neutron rich arsenic isotopes are studied by the Se( $t$ , ${}^{3}{He}$ ) As reactions. In ${}^{78}{As}$ , 33 levels up to $E_{x} = 2383$ keV are identified. In ${}^{80, 82}{As}$ where no levels have previously been assigned, 18 and 9 levels respectively were observed. A mass excess of -72182±20 keV is obtained for ${}^{80}{As}$ which disagrees substantially with recent $β$ -decay measurements. For ${}^{82}{As}$ the measured mass excess is -70067±27 keV which differs by 300 keV from previous measurements.

NUCLEAR REACTIONS ${}^{78}{Se}$ ( $t$ , ${}^{3}{He}$ ), ${}^{80}{Se}$ ( $t$ , ${}^{3}{He}$ ), ${}^{82}{Se}$ ( $t$ , ${}^{3}{He}$ ), $E = 23.0$ MeV; measured $σ (θ)$ . ${}^{78}{As}$ , ${}^{80}{As}$ , ${}^{82}{As}$ deduced levels. New masses of ${}^{80}{As}$ , ${}^{82}{As}$ .

Four-nucleon pickup from ${}^{14}N$

W. Oelert, A. Djaloeis, C. Mayer-Böricke, and P. Turek

Phys. Rev. C 19, 1747 (1979) - Published 1 April, 1979

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Spectroscopic factors for four-nucleon transfer have been extracted for states in ${}^{10}B$ populated via the ${}^{14}N$ ( $d$ , ${}^{6}{Li}$ ) reaction, at an incident energy of 80 MeV. The experimental angular distributions were analyzed in the framework of finite-range distorted wave Born approximation calculations. The results are compared to theoretical shell model predictions.

NUCLEAR REACTIONS ${}^{14}N$ ( $d$ , ${}^{6}{Li}$ ) ${}^{10}B$ ; $E_{d} = 80$ MeV measured $σ (E_{{}^{6}{Li}}, θ)$ . Gas target. Finite-range DWBA calculations.

${}^{79}{Br}$ and ${}^{81}{Br}$ ( $p$ , $xn$ ) and ( $p$ , $pxn$ ) excitation functions in the energy range 10-85 MeV

M. Dikšić, J. -L. Galinier, H. Marshall, and L. Yaffe

Phys. Rev. C 19, 1753 (1979) - Published 1 April, 1979

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A study of ( $p$ , $xn$ ) and ( $p$ , $pxn$ ) reactions on ${}^{79}{Br}$ and ${}^{81}{Br}$ was made. The excitation functions were measured in the energy range 10-85 MeV. The excitation functions experimentally obtained were compared with those predicted by intranuclear cascades and two pre-equilibrium models followed by equilibrium evaporation. None of the three computer codes was able to reproduce all excitation functions satisfactorily. The relative success of the computer codes tested is discussed.

NUCLEAR REACTIONS ${}^{79}{Br}$ ( $p$ , $n$ ), ( $p$ , $3 n$ ), ( $p$ , $4 n$ ), ( $p$ , $pn$ ), ( $p$ , $p 2 n$ ), ( $p$ , $p 3 n$ ), ( $p$ , $p 4 n$ ), ( $p$ , $p 5 n$ ). ${}^{81}{Br}$ ( $p$ , $3 n$ ), ( $p$ , $5 n$ ), ( $p$ , $6 n$ ), ( $p$ , $pn$ ), ( $p$ , $p 3 n$ ), ( $p$ , $p 4 n$ ), ( $p$ , $p 5 n$ ), ( $p$ , $p 6 n$ ), enriched target, $E = 10 - 85$ MeV, measured $σ (E)$ .

Gamma decay of $g_{\frac{9}{2}}$ isobaric analog resonance in ${}^{57}{Co}$

C. Rangacharyulu, I. M. Szöghy, C. Pierre, St-, and K. Ramavataram

Phys. Rev. C 19, 1762 (1979) - Published 1 April, 1979

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The isobaric analog resonance in ${}^{57}{Co}$ , corresponding to the $J^{π} = \frac{9}{2^{+}}$ parent state at 2.454 MeV in ${}^{57}{Fe}$ , has been located and its $γ$ decay to various $T_{<}$ levels studied by means of the ${}^{56}{Fe}$ ( $p$ , $γ$ ) ${}^{57}{Co}$ reaction. We have identified the level at 4.597 MeV in ${}^{57}{Co}$ as the antianalog state with $J^{π} = \frac{9}{2^{+}}$ . Additional information on the $M 1$ strength systematics in the isovectorial $\frac{9}{2^{+}} \to \frac{9}{2^{+}}$ transitions in the $f - p$ shell nuclei is provided.

NUCLEAR REACTIONS ${}^{56}{Fe}$ ( $p$ , $γ$ ) ${}^{57}{Co}$ , $E_{p} = 3.7 - 3.8$ MeV; measured $E_{γ}$ , $σ (E_{γ}, θ)$ , $\frac{Γ_{p} Γ_{γ}}{Γ_{tot}}$ . ${}^{57}{Co}$ deduced $E 1$ and $M 1$ strengths. $\frac{9}{2^{+}}$ analog and antianalog states. Enriched target.

Population of intrinsic high spin states with the direct ${}^{116}{Sn}$ ( $α$ , $p$ ) ${}^{119}{Sb}$ reaction

P. A. Smith, R. A. Emigh, N. J. DiGiacomo, G. R. Smith, and R. J. Peterson

Phys. Rev. C 19, 1767 (1979) - Published 1 April, 1979

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The ${}^{116}{Sn}$ ( $α$ , $p$ ) ${}^{119}{Sb}$ reaction at $E_{α} = 35.6$ MeV has been used to locate previously unknown high spin states in ${}^{119}{Sb}$ . Cluster distorted-wave Born-approximation calculations have been employed to identify $L = 10$ ( $J^{π} = \frac{19}{2^{+}}, \frac{21}{2^{+}}$ ) transfers to states at 4.120±0.015 and 4.210±0.015 MeV. A state located at 4.020±.015 MeV may be fit by either $L = 12 or 14$ distorted-wave Born-approximation curves. These high spin states are not members of the previously identified $K^{π} = \frac{9}{2^{+}}$ rotational band. No evidence for population of this $\frac{9}{2^{+}}$ band was observed. Residual interaction matrix elements for the ${(ν h_{\frac{11}{2}} π s_{\frac{1}{2}})}_{5^{-}, 6^{-}}$ configurations have been deduced, assuming simple wave functions for the states populated by $L = 10$ transfers. The resulting matrix elements are in excellent agreement with the predictions of a $δ$ force, as are other matrix elements extracted from the odd-odd Sb spectra.

NUCLEAR REACTIONS ${}^{116}{Sn}$ ( $α$ , $p$ ) ${}^{119}{Sb}$ , separated isotope, measured $σ (E_{p}, θ)$ , cluster DWBA analysis, deduced residual interaction matrix elements.

$α$ clustering in ${}^{208}{Pb}$ from ( $d$ , ${}^{6}{Li}$ ) at $E_{d} = 55$ MeV

F. D. Becchetti, J. Jänecke, D. Overway, J. D. Cossairt, and R. L. Spross

Phys. Rev. C 19, 1775 (1979) - Published 1 April, 1979

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The reaction ${}^{208}{Pb}$ ( $d$ , ${}^{6}{Li}$ ) ${}^{204}{Hg}$ has been observed at $E_{d} = 55$ MeV. Data for several levels in ${}^{204}{Hg}$ up to $E_{x} ≃ 3.5$ MeV have been obtained and alpha-particle spectroscopic factors and reduced alpha widths for ${}^{208}{Pb}$ deduced with distorted-wave Born approximation analyses. The reduced alpha widths have been utilized to deduce the "alpha decay" properties of ${}^{208}{Pb}$ , as well as superheavy nuclei. The analysis indicates $log {T^{α}}_{\frac{1}{2}} (years) = 127.4 \pm 1.0$ for ${}^{208}{Pb}$ and $log {T^{α}}_{\frac{1}{2}} (years) = 2.5 \pm 2.0$ for $Z = 114$ , $N = 184$ and $Q_{α} = 7.0 \pm 0.5$ MeV. The results also imply that about 1% of the protons in ${}^{208}{Pb}$ at $r = 10$ fm are associated with alpha clusters.

NUCLEAR REACTIONS ${}^{108}{Pb}$ ( $d$ , ${}^{6}{Li}$ ) ${}^{204}{Hg}$ , $E = 54.8$ MeV; measured $σ (θ)$ . ${}^{204}{Hg}$ deduced levels, $S_{α}$ , $γ_{α}^{2} (10 fm)$ . DWBA analyses. Magnetic spectrometer.

Decay modes of analog states studied by the ( ${}^{3}{He}$ , $dp$ ) reaction

G. Finkel, D. Ashery, A. I. Yavin, A. Boudard, G. Bruge, A. Chaumeaux, and M. Rouger

Phys. Rev. C 19, 1782 (1979) - Published 1 April, 1979

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The ( ${}^{3}{He}$ , $dp$ ) reaction was studied at 30-MeV bombarding energy on ${}^{60}{Ni}$ , ${}^{62}{Ni}$ , and ${}^{90}{Zr}$ . Protons were detected in coincidence with deuterons at various angles, in and out of the reaction plane. Angular correlations were measured between the deuterons populating analog states and the protons associated with the decay of the analog states to several states in the final nucleus. Spectroscopic information is derived from the analysis of the measured angular correlations on ten analog states: three in ${}^{61}{Cu}$ , four in ${}^{63}{Cu}$ , and three in ${}^{91}{Nb}$ .

NUCLEAR REACTIONS ${}^{60, 62}{Ni}$ , ${}^{90}{Zr}$ ( ${}^{3}{He}$ , $dp$ ), $E = 30.2$ MeV; measured coincidence $σ (E_{d}, E_{p}, θ_{p})$ . Deduce spectroscopic information IAS in ${}^{61, 63}{Cu}$ , ${}^{91}{Nb}$ . Enriched targets. Calculate angular correlation function.

New isotope ${}^{242}{Bk}$

Kimberly E. Williams and Glenn T. Seaborg

Phys. Rev. C 19, 1794 (1979) - Published 1 April, 1979

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A new isotope of berkelium has been identified through bombardments of ${}^{235}U$ with ${}^{11}B$ , ${}^{238}U$ with ${}^{10}B$ , and ${}^{232}{Th}$ with both ${}^{14}N$ and ${}^{15}N$ . The new activity decays by electron capture with a half-life of 7.0±1.3 minutes. The $α$ -branching ratio for this isotope is less than 1% and that for spontaneous fission is less than 0.03%. Analysis of the excitation functions, the chemical behavior of the isotope, and the milking of the ${}^{242}{Cm}$ daughter leads to the positive identification of this isotope as ${}^{242}{Bk}$ . A preliminary search was made for ${}^{241}{Bk}$ but was unsuccessful. Examination of the (heavy ion, $pxn$ ) (Cm) and (heavy ion, $α xn$ ) (Am) transfer products in comparison with the (heavy ion, $xn$ ) (Bk) compound nucleus products produced in the above reactions revealed transfer reaction cross sections to be equal to or greater than the compound nucleus cross sections. The data suggest that in some cases the yield of an isotope produced via a $pxn$ or $α xn$ transfer reaction might be higher than its production via an $xn$ compound nucleus reaction.

NUCLEAR REACTIONS Compound nucleus, proton and alpha transfer reactions: ${}^{235}U ({}^{10, 11}B, X) I$ ; ${}^{238}U ({}^{10}B, Q) R$ ; ${}^{232}{Th} ({}^{14, 15}N, M) T$ ; measured excitation functions for ${}^{242}{Bk}$ ; measured $σ$ for ${}^{238}{Am}$ , ${}^{239}{Am}$ , ${}^{240}{Am}$ , ${}^{240}{Cm}$ , ${}^{242}{Cm}$ , ${}^{243}{Bk}$ .

Contribution to the heavy-ion optical potential from coupling to vibrational states

R. Donangelo, L. F. Canto, and Mahir S. Hussein

Phys. Rev. C 19, 1801 (1979) - Published 1 April, 1979

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The component of the optical in the elastic channel due to the coupling to vibrational states in Coulomb excitation is derived using a previously developed semiclassical method. Several numerical examples are worked out.

NUCLEAR REACTIONS Heavy-ion optical potential. Effect of coupling to vibrational states has been calculated.

Dependence of neutron yield on fragment mass for several low-energy fissioning systems

J. Gindler

Phys. Rev. C 19, 1806 (1979) - Published 1 April, 1979

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Neutron-yield functions for ${}^{245}{Cm}$ ( $n$ , $f$ ), ${}^{252}{Cf}$ (sf), ${}^{254}{Cf}$ (sf), ${}^{254}{Es}$ ( $n$ , $f$ ), and ${}^{256}{Fm}$ (sf) are derived with an iterative method in which successive approximations to the pre-neutron-emission (initial) mass distribution are compared with the post-neutron-emission (final) mass distribution. Initial mass distributions are deduced from kinetic energy measurements of the fragments. Final mass distributions are determined from radiochemical measurements of fission product mass yields. The ${}^{252}{Cf}$ (sf) neutron-yield function so derived agrees well with functions determined directly by neutron counting. All neutron-yield functions exhibit a saw-toothed character. The masses for which maximum neutron emission occurs and for which minimum neutron emission occurs are within ± 2 mass units of being complementary masses for the observed fissioning system, with the exception of the ${}^{245}{Cm}$ ( $n$ , $f$ ) reaction. The effect of the neutron-yield function on various mass and energy correlations deduced from kinetic energy measurements is discussed.

NUCLEAR REACTIONS, FISSION ${}^{254}{Cm}$ ( $n$ , $f$ ), ${}^{252}{Cf}$ (sf), ${}^{254}{Cf}$ (sf), ${}^{254}{Es}$ ( $n$ , $f$ ), ${}^{256}{Fm}$ (sf). Deduced neutron yields, fragment mass and energy distributions.

Three-hump fission barrier in ${}^{232}{Th}$

B. S. Bhandari

Phys. Rev. C 19, 1820 (1979) - Published 1 April, 1979

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Subbarrier photofission cross-sections and the fission half-lives have been calculated for ${}^{232}{Th}$ in terms of a suitable three-hump fission barrier model consistent with the suggestion of Möller and Nix. The competition due to the gamma deexcitation to the shape-isomeric state in the second well (and its consequent fission) has been included by introducing an absorptive part in the potential in the second well region. The calculated cross sections reproduce satisfactorily the recently observed "shelf" in the deep-subbarrier energy region and provide a further quantitative evidence in favor of resolving the "thorium anomaly" along the lines suggested by Möller and Nix.

NUCLEAR REACTIONS Fission, calculated subbarrier photofission cross-sections and fission half-lives using a three-hump fission barrier in ${}^{232}{Th}$ . Results reproduce the observed "shelf" in the cross-sections in deep-subbarrier energy region.

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Physical Review C

Recent Articles

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Separable expansions to local potentials in a quasipotential approach

$R$ -matrix method for nuclear reaction theory

Photonuclear cross sections for ${}^{18}O$

Photoneutron cross sections for ${}^{13}C$

Interaction current effects in proton-neutron bremsstrahlung

Structure in the giant resonance region of ${}^{16}O$ observed with the reaction ${}^{13}C$ ( ${}^{3}{He}$ , $γ$ ) ${}^{16}O$

Four-body model of the four-nucleon system

Method for scattering equations

${}^{72}{Ge}$ from the ${}^{70}{Ge}$ ( $t$ , $p$ ) reaction

Levels in ${}^{78, 80, 82}{As}$ from the ${}^{78, 80, 82}{Se}$ ( $t$ , ${}^{3}{He}$ ) reactions

Four-nucleon pickup from ${}^{14}N$

${}^{79}{Br}$ and ${}^{81}{Br}$ ( $p$ , $xn$ ) and ( $p$ , $pxn$ ) excitation functions in the energy range 10-85 MeV

Gamma decay of $g_{\frac{9}{2}}$ isobaric analog resonance in ${}^{57}{Co}$

Population of intrinsic high spin states with the direct ${}^{116}{Sn}$ ( $α$ , $p$ ) ${}^{119}{Sb}$ reaction

$α$ clustering in ${}^{208}{Pb}$ from ( $d$ , ${}^{6}{Li}$ ) at $E_{d} = 55$ MeV

Decay modes of analog states studied by the ( ${}^{3}{He}$ , $dp$ ) reaction

New isotope ${}^{242}{Bk}$

Contribution to the heavy-ion optical potential from coupling to vibrational states

Dependence of neutron yield on fragment mass for several low-energy fissioning systems

Three-hump fission barrier in ${}^{232}{Th}$

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