Recent Articles

Mass distribution in the neutron induced fission of ${}^{232}U$

S. B. Manohar, P. P. Venkatesan, S. M. Deshmukh, Satya Prakash, and M. V. Ramaniah

Phys. Rev. C 19, 1827 (1979) - Published 1 April, 1979

Show Abstract

Mass distribution in the neutron induced fission of ${}^{232}U$ has been studied. The distribution though predominantly asymmetric shows the existence of a small symmetric peak. The average fission product masses for the light and heavy wing are 92.7 and 137.5 mass units, respectively. The widths of the distribution at half and one tenth maxima are 13.4 and 21.0 mass units, respectively, and the peak to valley ratio of yields is about 480. An analysis of the factors influencing the probability of the existence of a symmetric peak and the variation of peak to valley ratio as a function of the proton and neutron numbers of the fissioning nucleus has shown that these variations can be qualitatively explained on the basis of differences in the heights of symmetric and asymmetric outer barriers.

NUCLEAR REACTION, FISSION ${}^{232}U$ ( $n$ , $f$ ) obtained mass yield using radiochemical and gamma spectrometric techniques, general features examined in terms of symmetric and asymmetric outer barrier heights.

Differential ranges and angular distributions of Ba fragments from the interaction of ${}^{238}U$ with 11.5-GeV protons

N. T. Porile, S. Pandian, H. Klonk, C. R. Rudy, and E. P. Steinberg

Phys. Rev. C 19, 1832 (1979) - Published 1 April, 1979

Show Abstract

Angular distributions and differential ranges at 90° to the beam direction have been measured for the following products from the interaction of ${}^{238}U$ with 11.5-GeV protons: ${}^{128}{Ba}$ , ${}^{131}{La}$ , ${}^{131}{Ba}$ (independent), ${}^{135}{Ba}^{m}$ , and ${}^{140}{Ba}$ . All the angular distributions peak at sideward angles. A two-parameter ( $n_{∥}$ and $\frac{b}{a}$ ) fit to the angular distributions based on the two-step model yields an anisotropy parameter, $\frac{b}{a}$ , of ∼ -0.2 for all products. The value of $〈 v_{∥} 〉$ . the mean forward component of velocity of the struck nuclei, is also insensitive to the composition of the observed products. A sharp transition in the momentum spectra derived from the differential ranges is observed just over one $Z$ unit to the neutron-deficient side of stability. Products on the neutron-rich side of this transition have narrow, symmetric spectra, with mean values of $\sim 130 {(MeV A)}^{\frac{1}{2}}$ , that are characteristic of fission. Products on the neutron deficient side have broad, asymmetric spectra, with a mean value of only $\sim 70 {(MeV A)}^{\frac{1}{2}}$ , as expected for a deep spallation mechanism. The spectrum of independently formed ${}^{131}{Ba}$ , which lies in the transition region, was decomposed into fission and deep spallation contributions, with the latter accounting for most of the cross section.

NUCLEAR REACTIONS ${}^{238}U$ ( $p$ , $x$ ) ${}^{128}{Ba}$ , ${}^{131}{La}$ , ${}^{131}{Ba}$ , ${}^{135}{Ba}^{m}$ , ${}^{140}{Ba}$ , $E_{p} = 11.5$ GeV; measured angular distributions and differential ranges at 90°; inferred momentum spectra.

Composite-particle structure of pion-nucleus amplitudes

K. L. Kowalski, E. R. Siciliano, and R. M. Thaler

Phys. Rev. C 19, 1843 (1979) - Published 1 April, 1979

Show Abstract

The structural properties of scattering amplitudes which involve composite particles are applied to pion absorption on and elastic scattering from nuclei. The reactive parts, as opposed to the initial and final state parts, of the amplitudes for these processes are identified and the constraints upon their structure are investigated. These constraints are used to determine the modifications, in various models for pionic interactions, which are necessary to avoid double-counting dynamics already accounted for in the nuclear states. The previously known decomposition of the elastic pion-nucleus scattering amplitude into the contributions from scattering and true absorption is derived in a general context. We go on to point out the structural features of both of these parts of the elastic amplitude which are required in order not to duplicate nuclear dynamics.

NUCLEAR REACTIONS Pion absorption on nuclei. Pion elastic scattering from nuclei. Composite particle scattering theory.

Neutron isotopic density differences deduced from 0.8 GeV polarized proton elastic scattering

L. Ray

Phys. Rev. C 19, 1855 (1979) - Published 1 April, 1979

Show Abstract

The microscopic spin-independent proton-nucleus optical potential defined by Kerman, McManus, and Thaler is used to analyze recent 0.8 GeV polarized proton elastic scattering data from ${}^{40, 48}{Ca}$ , ${}^{58, 64}{Ni}$ , ${}^{116, 124}{Sn}$ , and ${}^{208}{Pb}$ . Second-order effects due to target nucleon correlations are included in both the central and spin-orbit parts of the proton-nucleus optical potential. Electromagnetic corrections to the proton density which arise from the electric and magnetic form factors of the neutron, and from the magnetic form factor of the proton, are also calculated. A discussion is presented regarding uncertainties in the nucleon-nucleon amplitudes used in construction of the potential, and also discrete ambiguities which arise from fitting the limited set of nucleon-nucleon data available near 1 GeV are examined. Approximately model-independent forms are assumed for the target neutron density distributions, thereby allowing the statistical and model-dependence errors to be estimated. Neutron density and rms radii are deduced and compared to Hartree-Fock predictions, with good agreement found for most of the seven nuclei studied. Because of the uncertainty in the proton-nucleon amplitudes, neutron density and radius differences are considered more reliable than individual absolute values. Owing to the inclusion of certain second-oŕder terms discussed here, an accurate determination of these differences is obtained.

NUCLEAR REACTIONS proton-nucleus scattering, $E_{p} = 0.8$ GeV; targets ${}^{40, 48}{Ca}$ , ${}^{58, 64}{Ni}$ , ${}^{116, 124}{Sn}$ , and ${}^{208}{Pb}$ ; Kerman, McManus and Thaler optical potential; target nucleon correlations; electromagnetic corrections; deduced neutron density distributions and radii.

Pion absorption by deuterons in field theory

Roger H. Hackman

Phys. Rev. C 19, 1873 (1979) - Published 1 April, 1979

Show Abstract

Using non-perturbative, field-theoretic techniques based on a generalization of the Low equation, an inhomogeneous, coupled, linear, integral equation is developed for the reaction matrix for $π d \to 2 p$ . The inhomogeneous term in this equation consists of a truncated, multiple-scattering expansion of the breakup process. The integral terms couple the reaction to elastic nucleon-nucleon and elastic pion-deuteron scattering. The inhomogeneous term is evaluated at the reaction threshold, with relativistic forms for the absorption and rescattering vertices. $P$ -wave pion-nucleon rescattering is found to make a non-negligible contribution to the $s$ -wave absorption process at threshold.

NUCLEAR REACTIONS $d (π^{+}, p p)$ , generalized Low equation, pion crossing, calculated threshold $σ$ .

Two-neutron emission in the absorption of stopped pions on lithium isotopes

B. Bassalleck, E. L. Haase, W. -D. Klotz, F. Takeutchi, H. Ullrich, M. Furic, and Y. Sakamoto

Phys. Rev. C 19, 1893 (1979) - Published 1 April, 1979

Show Abstract

The ( $π^{-}$ , $2 n$ ) reaction on ${}^{6}{Li}$ and ${}^{7}{Li}$ nuclei has been studied in a kinematically complete experiment. Distributions of excitation energy of residual nuclei, of recoil momentum, and of angle spanned by relative and c.m. momenta of emitted neutrons have been extracted. The reaction mechanism has been investigated through a comparison with theoretical predictions.

NUCLEAR REACTIONS ( $π^{-}$ , $2 n$ ) on ${}^{6}{Li}$ and ${}^{7}{Li}$ , $E = 0$ measured rate ( $E n_{1}$ , $E n_{2}$ , $ω$ ); excitation spectra for residual nuclei deduced, recoil momentum distributions and correlations of relative and c. m. momenta of emitted neutrons extracted.

Decays of the lowest $T = 2$ states in $A = 4 N$ nuclei from ${}^{8}{Be}$ to ${}^{44}{Ti}$

S. J. Freedman, C. A. Gagliardi, M. A. Oothoudt, A. V. Nero, R. G. H. Robertson, F. J. Zutavern, E. G. Adelberger, and A. B. McDonald

Phys. Rev. C 19, 1907 (1979) - Published 1 April, 1979

Show Abstract

Branching ratios for isospin-forbidden decays have been measured for the lowest $T = 2$ levels in ${}^{8}{Be}$ , ${}^{12}C$ , ${}^{16}O$ , ${}^{24}{Mg}$ , ${}^{28}{Si}$ , ${}^{32}S$ , ${}^{36}{Ar}$ , ${}^{40}{Ca}$ , and ${}^{44}{Ti}$ . The $T = 2$ levels were populated by the isospin allowed ( $p$ , $t$ ) reaction at $E_{p} = 42 or 46$ MeV. Coincidences were observed between tritons detected in a quadrupole-dipole-dipole-dipole magnetic spectrometer and decay particles detected in a surface-barrier detector telescope, a time-of-flight neutron detector, or an NaI (Tl) $γ$ -ray detector. Systematics of isospin-forbidden decay widths are discussed.

NUCLEAR STRUCTURE ${}^{8}{Be}$ , ${}^{12}C$ , ${}^{16}O$ , ${}^{24}{Mg}$ , ${}^{28}{Si}$ , ${}^{32}S$ , ${}^{36}{Ar}$ , ${}^{40}{Ca}$ , ${}^{44}{Ti}$ ; lowest $J^{π} = 0^{+}$ , $T = 2$ level; measured isospin-forbidden particle-decay branching ratios.

Screening effects in radiative orbital electron capture by an atomic nucleus

Z. R. Iwinski, Young Soon Kim, and R. H. Pratt

Phys. Rev. C 19, 1924 (1979) - Published 1 April, 1979

Show Abstract

Using the results of an analytic perturbation theory for screened Coulomb wave functions, closed-form expressions are given for screening corrections to internal bremsstrahlung accompanying nuclear capture from $ns$ and $2 p$ states within nonrelativistic dipole approximation. The analytic perturbation theory is based on the expansion of the potential in the interior of an atom as a series of the form $V (r) = - (\frac{a}{r}) [1 + V_{1} λ r + V_{2} {(λ r)}^{2} + V_{3} {(λ r)}^{3} + \dots]$ , where $a = Z α, λ$ is a $Z$ -dependent small parameter characterizing the screening, and the coefficients $V_{k}$ are of order unity. The nonrelativistic screened Coulomb Green's function, needed for the calculations of the matrix elements, is obtained as a series in $λ$ with analytic coefficients. The screening correction to radiative capture from $ns$ -states, in agreement with the arguments of Glauber and Martin, is simply the energy independent, multiplicative factor of the ratio of screened to unscreened bound state normalization. In radiative capture from the $2 p$ state there are additional energy dependent screening corrections, largest near the resonance at an energy corresponding to characteristic x-ray radiation (due to the shift of the resonance energy position with screening), which decrease to less than 1% for photon energies several times larger than the energy of the resonance. The relation between the screening corrections to radiative capture from the $2 p$ state at resonance and to the $2 p - 1 s$ bound-bound radiative transition serves as a check of the calculation. From the screened Green's function the Fermi-Segrè formula, connecting the $ns$ -bound state energy shifts and the bound state normalizations, is rederived, together with a generalization to arbitrary angular momentum states.

RADIOACTIVITY Screening corrections to internal bremsstrahlung accompanying nuclear capture of an orbital electron from $ns$ and $2 p$ states within nonrelativistic dipole approximation.

Yrast states in ${}^{52}{Fe}$ , ${}^{52}{Mn}$ and the decay of ${}^{52}{Fe}^{m}$

D. F. Geesaman, R. L. McGrath, J. W. Noé, and R. E. Malmin

Phys. Rev. C 19, 1938 (1979) - Published 1 April, 1979

Show Abstract

The properties of yrast states of ${}^{52}{Fe}$ and ${}^{52}{Mn}$ were studied using the ${}^{40}{Ca}$ + ${}^{14}N$ reaction. In-beam $γ$ -ray singles, $γ - γ$ coincidence, and $n - γ$ coincidence data establish the positions of the lowest $2^{+}$ and $4^{+}$ states of ${}^{52}{Fe}$ as 849.1±0.3 and 2384.6±0.7 keV, respectively. No $γ$ rays associated with other ${}^{52}{Fe}$ states could be found. This is because an ${}^{52}{Fe}$ isomer at 6.83 MeV $β^{+}$ decays to ${}^{52}{Mn}$ , diverting strength from the ${}^{52}{Fe}$ $γ$ cascade. Delayed $γ$ -ray singles and $γ - γ$ coincidence data give information on the high-spin yrast states of ${}^{52}{Mn}$ populated in the $β^{+}$ decay of the isomer. The results are consistent with several recently published works, and unambiguously establish that the ${}^{52}{Mn}$ $8^{+}$ state is at 2286.0±0.4 keV. The delayed spectra show no indication of direct $γ$ decay of the ${}^{52}{Fe}$ isomer. An upper limit on the $γ$ decay branch is 4 × $10^{- 3}$ . On the basis of the ${(1 f_{\frac{7}{2}})}^{n}$ model with "bare" nucleon charges, direct $E 4$ $γ$ emission should be the dominant decay mode. It is argued that the absence of $E 4$ decay, taken together with known $B (E 4)$ data on ${}^{44}{Sc}$ , ${}^{52}{Mn}$ and ${}^{53}{Fe}$ , shows $E 4$ effective charges in the ( $1 f_{\frac{7}{2}}$ ) shell are different for nuclei located near the beginning or end of the shell. Further, the effective charges near the end of the shell seem to be quite different from those found in $E 2$ transitions, i.e., $e_{p} \sim 0.5$ , $e_{n} \sim - 0.5$ . First order perturbation calculations in the ${(1 f, 2 p)}^{n}$ model offer qualitative, but not quantitative, insight as to the $E 4$ effective charge behavior.

RADIOACTIVITY ${}^{52}{Fe}^{m}$ ; measured $T_{\frac{1}{2}}$ . $β γ$ coin., $β$ -delayed $γ$ and $γ γ$ coin; deduced $log ft$ , $E 4$ limit. ${}^{52}{Mn}$ deduced levels.

NUCLEAR REACTIONS ${}^{40}{Ca}$ ( ${}^{14}N$ , $np$ ) ${}^{52}{Fe}$ , $E = 29 to 38$ MeV; measured prompt $γ$ and $n γ$ coinc., deduced ${}^{52}{Fe}$ levels.

Half-life measurements of Rb, Sr, Y, Cs, Ba, La and Ce isotopes with $A = 91 - 98$ and $A = 142 - 149$

G. Engler, Y. Nir-El, M. Shmid, and S. Amiel

Phys. Rev. C 19, 1948 (1979) - Published 1 April, 1979

Show Abstract

Half-lives of the extremely neutron-rich isotopes ${}^{91 - 98}{Rb}$ , ${}^{94 - 98}{Sr}$ , ${}^{96 - 98}Y$ , ${}^{142 - 146}{Cs}$ , ${}^{143 - 148}{Ba}$ , ${}^{144 - 149}{La}$ , and ${}^{149}{Ce}$ were determined. The isotopes ${}^{147, 148}{Ba}$ , and ${}^{149}{La}$ were identified for the first time and their half-lives measured. The values obtained, in seconds, are 0.72±0.07 for ${}^{147}{Ba}$ , 0.47±0.20 for ${}^{148}{Ba}$ and 1.2±0.4 for ${}^{149}{La}$ . The other measured half-lives either confirm or improve previous measurements. An extrapolation procedure based on the systematic behavior of experimental half-lives for the prediction of half-lives not yet measured was used. Similar systematic behavior is also apparent for half-lives predicted within the framework of the gross theory of $β$ decay.

RADIOACTIVITY ${}^{91 - 98}{Rb}$ , ${}^{94 - 98}{Sr}$ , ${}^{96 - 98}Y$ , ${}^{142 - 146}{Cs}$ , ${}^{143 - 148}{Ba}$ , ${}^{144 - 149}{La}$ , ${}^{149}{Ce}$ [from ${}^{235}U$ ( $n$ , fission)]; measured $T_{\frac{1}{2}}$ . Si surface barrier detector. Mass-separated Rb, Sr, Cs, and Ba activities.

$J$ -averaged behavior of the core polarization through third order for excitations up to $10 ℏ ω$

J. Chai and S. A. Moszkowski

Phys. Rev. C 19, 1953 (1979) - Published 1 April, 1979

Show Abstract

The effect of second order $J$ -averaged core polarization on shell model matrix elements was examined through $10 ℏ ω$ for the intermediate state excitations. It was found that for ${}^{34}{Cl} [{({Od}_{\frac{3}{2}})}^{2}]$ the present treatment was quite adequate to provide the needed average repulsion in $T = 1$ states, while for ${}^{40}{Ca} [({Od}_{\frac{3}{2}}^{- 1} {Of}_{\frac{7}{2}})]$ the perturbation treatment fell short by about 0.8 MeV. The tensor effect on higher shell intermediate state excitations was also studied and was found to be more marked for ( ${Od}_{\frac{3}{2}}^{- 1} {Of}_{\frac{7}{2}}$ ). Two particularly large third order terms in the perturbation expansion of the effective interactions were also calculated. Their $J$ -averaged effects on ${({Od}_{\frac{3}{2}})}^{2}$ and ( ${Od}_{\frac{7}{2}}^{- 1}$ ) were found to be small and well-behaved. The $J$ -averaged tensor effect calculated in third order was found to saturate by about $10 ℏ ω$ .

NUCLEAR STRUCTURE Excitation spectra core polarization effective interactions.

Partially conserved axial-vector current and model chiral field theories in nuclear physics

David K. Campbell

Phys. Rev. C 19, 1965 (1979) - Published 1 April, 1979

Show Abstract

We comment on the relation between the two standard approaches to chiral symmetry-namely, the current algebra/partially conserved axial-vector current approach and the chiral Lagrangian method-in a manner intended to clarify recent and probable future applications of this symmetry in nuclear physics. Specifically, we show that in explicit chiral field theories the canonical $π N$ scattering amplitude does not have the famed "Adler zero" unless partial conservation of axial-vector current holds as an operator equation. This implies that there are a number of familiar chiral models in which the "Adler self-consistency" condition does not apply to the canonical pion field. Among the problems of current interest for which our remarks are relevant are the studies of the pion-nucleus optical potential, pion condensation, and the attempts to formulate a model field theory having both reasonable nuclear saturation and good low energy pion phenomenology.

NUCLEAR STRUCTURE Comparison of relation of pion field to axial-vector current in field theories of nuclear matter.

Time-dependent coupled-cluster approximation to nuclear dynamics. II. General formulation

P. Hoodbhoy and J. W. Negele

Phys. Rev. C 19, 1971 (1979) - Published 1 April, 1979

Show Abstract

A general formulation is presented of the time-dependent coupled-cluster hierarchy of equations introduced previously. Truncations appropriate to potentials with strongly repulsive cores are specified and the properties of the resulting equations of motion are discussed.

NUCLEAR STRUCTURE. Time-dependent approximations to nuclear dynamics. Generalized time-dependent Hartree-Fock and Bethe-Goldstone equations.

Extended-Skyrme-force calculation: Theoretical description and application to Ca and Sn isotopes

M. Waroquier, J. Sau, K. Heyde, P. Van Isacker, and H. Vincx

Phys. Rev. C 19, 1983 (1979) - Published 1 April, 1979

Show Abstract

The original Skyrme force is extended by a momentum dependent three-body term. A study is made on its influence on nuclear matter properties and properties of finite nuclei. The problem of spin-instability is treated in two nuclear models. A force parametrization is proposed, giving good estimates for all nuclear matter quantities (binding energy per nucleon, incompressibility, reduced mass, isospin symmetric energy, etc.), as well as properties of finite nuclei throughout the whole mass region (ground-state energy, nucleon distributions, rms radii, single-particle removal energies, etc.). The proposed parametrization satisfies the spin stability conditions. The force is able to describe satisfactorily the ground-state properties, even fine effects of two nuclear mass regions, one belonging to the light mass region ( $A = 40 - 48$ ) and one belonging to the medium heavy mass region ( $A = 104 - 132$ ).

NUCLEAR STRUCTURE Skyrme force extended with momentum dependent three-body term, spin stability conditions, application to Ca and Sn isotopes.

Nonlinear generalization of the quasiparticle random phase approximation for description of anharmonic effects in vibrational nuclei: Method

C. T. Li, P. K. Chattopadhyay, Abraham Klein, and M. J. Vassanji

Phys. Rev. C 19, 2002 (1979) - Published 1 April, 1979

Show Abstract

A nonlinear generalization of the quasiparticle random phase approximation is constructed with the aim of describing anharmonic effects in the low-lying spectra of vibrational nuclei. Angular momentum zero pairing correlations of the ground state are described by a generalized BCS calculation based on a variational method. The dynamics of the vibrational states are described by the Heisenberg equations of motion for fermion pair operators; matrix elements of products of pair operators are treated by sum rule methods. Kinematical constraints are expressed by the algebra of the pair operators and by boson-like polynomial expansions for the quasiparticle conserving multipole operators in terms of the quasiparticle pair changing operators, these expansions enforcing the content of the Pauli principle. The physical basis for the choice of approximations is described. The final algorithm is organized so as to involve little more than repeated BCS-like and RPA-like calculations, converging to a self-consistent solution of the full nonlinear scheme. Detailed discussion is carried out for a modified form of the pairing plus quadrupole interaction Hamiltonian, but the method is not confined to this model.

NUCLEAR STRUCTURE Approximate many-body methods applied to modified pairing plus quadrupole model. Description of vibrational spectrum of single closed shell nuclei. Equations of motion and algebraic methods.

Nonlinear generalization of the quasiparticle random phase approximation for description of anharmonic effects in vibrational spectra: Application to the even Ni isotopes

C. T. Li and Abraham Klein

Phys. Rev. C 19, 2023 (1979) - Published 1 April, 1979

Show Abstract

The theory of anharmonic nuclear vibrational motion (nonlinear equations-of-motion method) developed in the preceding paper is applied to ${}^{60, 62, 64}{Ni}$ , which exhibit one and two phonon quadrupole collective states. A model Hamiltonian consisting of a modified pairing plus quadrupole interaction is studied first by comparing the results of the nonlinear equations-of-motion method with those of an exact diagonalization. Contrary to popular opinion, the model chosen fails to produce a vibrational spectrum, except in the case of ${}^{60}{Ni}$ , and, as a consequence, the nonlinear equations-of-motion method, designed specifically to describe vibrational spectra, accords well with the exact calculations only for this case. A simple method is then described, within the framework of the nonlinear equations-of-motion method, for refining the model Hamiltonian so as to bring it into accord with experiment. In practice, it is found that a simple additional parameter in the Hamiltonian suffices to yield descriptions of the quadrupole states in Ni isotopes comparable in precision to the most up-to-date versions (modified, adjusted, etc.) of the surface delta interaction model.

NUCLEAR STRUCTURE Theory of anharmonic nuclear vibrations applied to ${}^{60, 62, 64}{Ni}$ . Modified pairing plus quadrupole interactions. Comparison with surface delta models.

${}^{3}H$ bound state for the Reid soft-core potential: Exact calculation by a perturbational approach

T. Sasakawa and T. Sawada

Phys. Rev. C 19, 2035 (1979) - Published 1 April, 1979

Show Abstract

The perturbational approach to the Faddeev equation proposed by us is applied to the ${}^{3}H$ bound state. The perturbation iteration is found to converge beautifully, leaving no question about its usefulness. Using the Reid soft-core potential, we obtain the ${}^{3}H$ binding energy at 6.62 MeV, $P (S) = 90.28 %$ , $P (S^{'}) = 1.70 %$ , and $P (D) = 8.02 %$ , for the three-body state consisting of the two-body pair in the ${}^{1}S_{0}$ and the ${}^{3}S_{1} = {}^{3}D_{1}$ state with the third particle in the $s$ -state relative to the center-of-mass of the pair. The contribution from the third particle in the $d$ -state adds to the binding energy only a small fraction (∼0.05 MeV). The one-body charge form factor of ${}^{3}{He}$ has a dip at $q^{2} \sim 16$ ${fm}^{- 2}$ , and the height of the second peak is about an order of magnitude too low compared to the data. Each Faddeev component of the triton wave function as a function of the relative distance of a pair has a node near the core radius in its ${}^{1}S_{0}$ and ${}^{3}S_{1}$ components, but no node is found in the ${}^{3}D_{1}$ component. The wave function as a function of the spectator coordinate extends over quite large distances without a node in any component. The nodes are attributed to the strong soft-core and the particle exchange effects.

NUCLEAR STRUCTURE Triton bound state. Exact solution of the Faddeev equation by a perturbative approach. Binding energy; 6.62 MeV. Node of the wave function near the core radius.

Nuclear level density in the ${}^{4}{He}$ system

J. J. Bevelacqua

Phys. Rev. C 19, 2050 (1979) - Published 1 April, 1979

Show Abstract

Level densities for the ${}^{4}{He}$ system are calculated within a $4 ℏ ω$ model space by utilizing a realistic nucleon-nucleon interaction. The fluctuations are smoothed with a least squares fitting procedure and exponential fits of the form $A \exp (\frac{E}{T})$ are calculated for the density and total number of levels. The total number of levels is also compared with the predictions of the equidistant model. Systematics of level densities for even-even nuclei for $4 \leq A \leq 66$ and for nuclei in general for $4 \leq A \leq 240$ are discussed.

NUCLEAR STRUCTURE ${}^{4}{He}$ , calculated $J^{π} = 0^{+}, 0^{-}, 1^{+}, 1^{-}, 2^{+}, 2^{-}, 3^{+}, 3^{-}, 4^{+}, 4^{-}, 5^{+}, 5^{-}, and 6^{+}$ levels up to 85 MeV excitation energy. Level density parameters are obtained for constant temperature and equidistant models.

Agreement of Hauser-Feshbach calculations with experiment for the reaction ${}^{14}N$ ( ${}^{14}N$ , $α$ ) ${}^{24}{Mg}$ at $E_{c . m .} = 10.1$ MeV

D. A. Viggars and I. M. Naqib

Phys. Rev. C 19, 2056 (1979) - Published 1 April, 1979

Show Abstract

Dissipation in time-dependent Hartree-Fock calculations

Kit-Keung Kan and Taro Tamura

Phys. Rev. C 19, 2058 (1979) - Published 1 April, 1979

Show Abstract

Dissipation is studied in a one-dimensional time-dependent Hartree-Fock system which simulates the capture of a slow neutron by a nucleus. It is shown that this time-dependent Hartree-Fock system is unable to approach thermodynamic equilibrium and that the time of damping of a collective vibration, induced by the capture, is much longer than the relaxation time of realistic nuclear collective motion. The dissipation in this time-dependent Hartree-Fock system is further compared with predictions of various one-body dissipation theories.

NUCLEAR REACTIONS time-dependent Hartree-Fock calculation, slow neutron capture, one-body dissipation.

Select page:

Physical Review C

Recent Articles

Filter

Recent Issues

Mass distribution in the neutron induced fission of ${}^{232}U$

Differential ranges and angular distributions of Ba fragments from the interaction of ${}^{238}U$ with 11.5-GeV protons

Composite-particle structure of pion-nucleus amplitudes

Neutron isotopic density differences deduced from 0.8 GeV polarized proton elastic scattering

Pion absorption by deuterons in field theory

Two-neutron emission in the absorption of stopped pions on lithium isotopes

Decays of the lowest $T = 2$ states in $A = 4 N$ nuclei from ${}^{8}{Be}$ to ${}^{44}{Ti}$

Screening effects in radiative orbital electron capture by an atomic nucleus

Yrast states in ${}^{52}{Fe}$ , ${}^{52}{Mn}$ and the decay of ${}^{52}{Fe}^{m}$

Half-life measurements of Rb, Sr, Y, Cs, Ba, La and Ce isotopes with $A = 91 - 98$ and $A = 142 - 149$

$J$ -averaged behavior of the core polarization through third order for excitations up to $10 ℏ ω$

Partially conserved axial-vector current and model chiral field theories in nuclear physics

Time-dependent coupled-cluster approximation to nuclear dynamics. II. General formulation

Extended-Skyrme-force calculation: Theoretical description and application to Ca and Sn isotopes

Nonlinear generalization of the quasiparticle random phase approximation for description of anharmonic effects in vibrational nuclei: Method

Nonlinear generalization of the quasiparticle random phase approximation for description of anharmonic effects in vibrational spectra: Application to the even Ni isotopes

${}^{3}H$ bound state for the Reid soft-core potential: Exact calculation by a perturbational approach

Nuclear level density in the ${}^{4}{He}$ system

Agreement of Hauser-Feshbach calculations with experiment for the reaction ${}^{14}N$ ( ${}^{14}N$ , $α$ ) ${}^{24}{Mg}$ at $E_{c . m .} = 10.1$ MeV

Dissipation in time-dependent Hartree-Fock calculations

Filter

Recent Issues

Filter

Article Lookup

Enter a citation