Recent Articles

Composite particle production in high-energy reactions and size of production source

K. Nakai, O. Terasaki, T. -A. Shibata, H. En'yo, and I. Arai

Phys. Rev. C 25, 1992 (1982) - Published 1 April, 1982

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Production cross sections of composite particles at $⊖_{lab} = 90 °$ (the target-rapidity region) from 12-GeV proton reaction on nuclear targets have been measured. The particle spectra were analyzed with the coalescence model, and the radius of the production source was deduced to be $R_{0}^{rms} = 1.7 \pm 0.5$ fm. The radius is significantly smaller than the nuclear radii, and is independent on the target nuclear mass within uncertainties.

NUCLEAR REACTIONS: Al, Cu, Ag, Ta $(p, x) p$ , $d$ , ${}^{3}{He}$ , ${}^{4}{He}$ , $E_{p} = 12$ GeV; measured $σ (\frac{p}{A}, ⊖ = 90 °)$ ; deduced size of emitting source.

Heavy fragment production through electropion excitation of ${}^{56}{Fe}$

S. P. Ahlen, P. B. Price, and M. Tincknell

Phys. Rev. C 25, 1996 (1982) - Published 1 April, 1982

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Heavy ejecta with charges ranging from $Z = 3 to 14$ have been observed following the collisions of 20 GeV electron with ${}^{56}{Fe}$ nuclei. Crude charge and energy spectra of the fragments have been determined with track-etch detectors. For $Z \leq 8$ , the source is found to be slowly moving ( $\frac{v}{c} < 0.004$ ) nuclear matter with a temperature of 13±1 MeV, quite similar to that responsible for the evaporation of nuclei excited by high-energy protons. The total cross section for producing fragments with $Z = 7 or 8 by 20$ GeV electrons is about 700 times smaller than that for producing these fragments through collisions of 2 GeV protons with iron nuclei. The excitation mechanism is most likely that of electropion production, as evidenced by the similarity of calculated and measured cross sections. An additional, as yet unknown, mechanism is required to explain the observed production of fragments with $Z \geq 12$ , energy > 140 MeV, and cross section of the order $10^{- 33}$ - $10^{- 32}$ ${cm}^{2}$ .

NUCLEAR REACTIONS ${}^{56}{Fe}$ ( $e$ , $X$ ), $E = 20$ GeV; Measured $σ (E_{X}, θ)$ for $X = L i, B e, B, C, N, a n d O$ . Determined temperature and velocity of source of fragments.

Spectroscopy of gamma rays from ${}^{78}{As}$ decay

B. Singh, D. A. Viggars, and H. W. Taylor

Phys. Rev. C 25, 2003 (1982) - Published 1 April, 1982

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Gamma rays accompanying the $β^{-}$ decay of ${}^{78}{As}$ to ${}^{78}{Se}$ have been studied using a high purity source and large volume germanium detectors. Seventeen new $γ$ rays have been observed and eight previously reported gamma rays have been excluded. From singles and $γ - γ$ coincidence data new levels are proposed at 1758.9, 2334.9, 2647.7, and 3372.7 keV, whereas the 1693-, 1721-, 2452-, 2798-, 3192-, 3528-, and 3984-keV levels proposed in earlier studies have been withdrawn from the ${}^{78}{As}$ decay scheme. Deduced $B (E 2)$ ratios have been compared with theoretical calculations based on an anharmonic oscillator model.

RADIOACTIVITY ${}^{78}{As}$ [from ${}^{78}{Se}$ ( $n$ , $p$ )]; measured $E_{γ}$ , $I_{γ}$ , $γ - γ$ coin; deduced: ${}^{78}{Se}$ levels, $B (E 2)$ ratios. Enriched ${}^{78}{Se}$ target, Ge and Ge(Li) detectors.

Excited $0^{+}$ states and electric monopole transitions in ${}^{118}{Sn}$

H. Kawakami, N. Yoshikawa, K. Komura, M. Koike, and H. Yamada

Phys. Rev. C 25, 2013 (1982) - Published 1 April, 1982

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Electric monopole transitions of 1758.04 ( $0_{1}^{+}$ - $0_{g}^{+}$ ), 2056.64 ( $0_{2}^{+}$ - $0_{g}^{+}$ ), and 298.58 keV ( $0_{2}^{+}$ - $0_{1}^{+}$ ) in ${}^{118}{Sn}$ were observed in the internal conversion electron spectra with a $π \sqrt{2}$ iron-free magnetic $β$ -ray spectrometer. Anisotropies of $γ - γ$ angular correlations were measured for the 0-2-0 spin sequence to confirm the excited $0^{+}$ states. The dimensionless ratio of $E 0$ to $E 2$ transition probabilities $X = \frac{B (E 0, 0^{+} - 0_{g}^{+})}{B (E 2, 0^{+} - 2_{1}^{+})}$ for the first, second, and third excited $0^{+}$ states were deduced as 0.0081±0.0008, 0.13±0.02, and <0.035, respectively. The relative monopole strength from the second excited $0^{+}$ state at 2056.6 keV was obtained as $\frac{ρ (0_{2}^{+} - 0_{1}^{+})}{ρ (0_{2}^{+} - 0_{g}^{+})} = 7.3 \pm 0.8$ .

RADIOACTIVITY ${}^{118}{Sb}$ (3.5 min) from ${}^{121}{Sb}$ ( $p$ , $4 n$ ) ${}^{118}{Te}$ - ${}^{118}{Sb}$ ; measured $I_{ce}$ , $I_{γ}$ , $γ - γ (θ)$ , ${}^{118}{Sn}$ observed $0^{+}$ levels, deduced branching ratio $X (\frac{E 0}{E 2})$ , relative monopole strength $ρ (E 0)$ . Natural target.

Interacting-boson-approximation $E 2$ operator in deformed nuclei

D. D. Warner and R. F. Casten

Phys. Rev. C 25, 2019 (1982) - Published 1 April, 1982

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The structure of the interacting boson approximation $E 2$ operator appropriate to deformed nuclei is investigated. It is shown that, in the SU(3) limit of the Hamiltonian, the relative $B (E 2)$ values of transitions between different representations of SU(3) are independent of the parametrization chosen for the operator. This feature leads to a better understanding of the geometrical analogs of the bands predicted by the interacting boson approximation. More generally, a study of empirical $B (E 2)$ values in the deformed rare earth nuclei indicates the suitability of an almost constant form for the $E 2$ operator across the region, and it is shown that the deduced form of the operator predicts very different features for the lowest $O^{+}$ excitation than those associated with the geometrical concept of a $β$ band.

NUCLEAR STRUCTURE Interacting boson approximation. Deduced structure of $E 2$ operator appropriate to deformed nuclei. Calculated $E 2$ matrix elements, $B (E 2)$ , branching ratios. Comparison with predictions of rotational model.

Electromagnetic sum rules by spectral distribution methods

T. R. Halemane and J. B. French

Phys. Rev. C 25, 2029 (1982) - Published 1 April, 1982

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The spectral distribution methods are applied to calculate non-energy-weighted and linear-energy-weighted sum rules for electric and magnetic multipole excitations in the $ds$ -shell nuclei ${}^{20}{Ne}$ , ${}^{24}{Mg}$ , ${}^{28}{Si}$ , ${}^{32}S$ , and ${}^{36}{Ar}$ . We see the inadequacy of $ds$ -shell model space to explain the observed isoscalar quadrupole transition strengths. Isospin admixing of $1^{+}$ levels in ${}^{24}{Mg}$ and ${}^{28}{Si}$ are also confirmed. For isovector $M 1$ , a detailed study of the Kurath sum rule is made. The strength sums for the higher order multipoles where experimental data are not accurate enough are also evaluated.

NUCLEAR STRUCTURE ${}^{20}{Ne}$ , ${}^{24}{Mg}$ , ${}^{28}{Si}$ , ${}^{32}S$ , ${}^{36}{Ar}$ ; sum rules for $E 2$ , $E 4$ , $M 1$ , $M 3$ , $M 5$ transitions; Brown-Kuo Hamiltonian; spectral distribution methods used for calculation; Kurath sum rule extended.

Structure of $N = 85$ nuclei within the cluster-phonon coupling model

H. Dias and F. Krmpotić

Phys. Rev. C 25, 2059 (1982) - Published 1 April, 1982

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The structure of the low-lying levels in $N = 85$ nuclei is discussed in the framework of the cluster-phonon coupling model. Excitation energies, one body reaction amplitudes, dipole and quadrupole moments, and $B (M 1)$ and $B (E 2)$ values are calculated and compared with the available experimental data.

NUCLEAR STRUCTURE ${}^{143}{Ce}$ , ${}^{145}{Nd}$ , ${}^{147}{Sm}$ , and ${}^{149}{Gd}$ ; calculated energy levels, $S$ , $Q$ , $μ$ , $B (E 2)$ , and $B (M 1)$ . Cluster-phonon coupling model.

Systematics of $E 2$ transition strengths in the Zn—Kr region

D. P. Ahalpara and K. H. Bhatt

Phys. Rev. C 25, 2072 (1982) - Published 1 April, 1982

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The observed electromagnetic properties, namely, (1) the $B (E 2)$ values for inband transitions in the collective bands of even-even isotopes ${}^{62 - 70}{Zn}$ , ${}^{66 - 78}{Ge}$ , ${}^{70 - 82}{Se}$ , and ${}^{74 - 86}{Kr}$ , and (2) their electric quadrupole moments of first $2^{+}$ states have been studied in the projected Hartree-Fock model. The calculations have been performed in the ( $1 p_{\frac{3}{2}} 0 f_{\frac{5}{2}} 1 p_{\frac{1}{2}} 0 g_{\frac{9}{2}}$ ) model space using Kuo-Brown effective interaction. The $E 2$ transition strengths have been studied for the yrast and yrare positive parity bands as well as for the recently observed negative parity collective bands. Using a simple structure for the collective band of states, namely, states with definite angular momentum projected from the lowest few deformed intrinsic Hartree-Fock states and using the effective charges $e_{p} = 1.6 e$ and $e_{n} = 1.0 e$ the observed systematics of $B (E 2)$ values are fairly well reproduced.

NUCLEAR STRUCTURE ${}^{62 - 70}{Zn}$ , ${}^{66 - 78}{Ge}$ , ${}^{70 - 82}{Se}$ , and ${}^{74 - 86}{Kr}$ .

Irreversible dynamics of quasispin systems

E. S. Hernández and H. G. Solari

Phys. Rev. C 25, 2087 (1982) - Published 1 April, 1982

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It is shown that nuclear matter described by quasispin or pseudospin operators may exhibit irreversible behavior, in the sense of modern kinetic theory. With the help of the group-contraction technique, a harmonic oscillator can be associated to the many-body system and it is seen that in the standard Lipkin-Meshkov-Glick model the ground-state phase transition gives rise to a significant change in the spectral properties of the characteristic operators. This fact makes room for the introduction of the microscopic operators of irreversible dynamics. Their meaning and the consequences of their existence are examined and it is seen that the time evolution of the quasispin arrangement closely resembles the approach to equilibrium of a macroscopic system.

NUCLEAR STRUCTURE Operators of irreversible Hamiltonian dynamics; quasispin nuclear matter; group contraction, Lipkin-Meshkov-Glick model; ground-state phase transition; entropy; irreversible approach to equilibrium.

Photoactivation of ${}^{111}{Cd}$

M. Krčmar, A. Ljubičić, K. Pisk, B. A. Logan, and M. Vrtar

Phys. Rev. C 25, 2097 (1982) - Published 1 April, 1982

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The photoactivation of the 396 keV ( $T_{\frac{1}{2}} \sim 49$ min) isomeric level has been studied with a ${}^{60}{Co}$ source. As in an earlier investigation of ${}^{115}{In}$ , evidence has been found for a nonresonant process contributing to the excitation of the isomeric level.

RADIOACTIVITY ${}^{111}{Cd}$ ; studied photoactivation with ${}^{60}{Co}$ , investigated reaction mechanism.

Excitation of the 10.212 MeV $1^{+}$ state in ${}^{48}{Ca}$ ( $p$ , $p^{'}$ ) at $E_{p} = 44.4$ MeV

G. P. A. Berg, W. Hürlimann, I. Katayama, S. A. Martin, J. Meissburger, J. Römer, B. Styczen, F. Osterfeld, G. Gaul, R. Santo, and G. Sondermann

Phys. Rev. C 25, 2100 (1982) - Published 1 April, 1982

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Differential cross sections of the ${}^{48}{Ca}$ ( $p$ , $p^{'}$ ) ( $1^{+}$ , 10.212 MeV) transition have been measured at $E_{p} = 44.4$ MeV using an isochronous cyclotron and a high resolution magnetic spectrometer. The data are compared to microscopic distorted-wave Born approximation calculations with wave functions taken from random phase approximation calculations.

NUCLEAR REACTIONS ${}^{48}{Ca}$ ( $p$ , $p^{'}$ ), $E = 44.4$ MeV; measured $σ (E; θ)$ ; microscopic DWBA analysis, resolution 7-10 keV; $θ = 7.3 - 80.0 °$ , $Δ θ = 4 - 5 °$ .

Analyzing power of the $\vec{p} p \to π^{+} d$ reaction at 400 and 450 MeV

W. R. Falk, E. G. Auld, G. Giles, G. Jones, G. J. Lolos, P. Walden, and W. Ziegler

Phys. Rev. C 25, 2104 (1982) - Published 1 April, 1982

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Analyzing power measurements of the $\vec{p} p \to π^{+} d$ reaction have been made at proton bombarding energies of 400 and 450 MeV, over the angular range from 76-119° center of mass. The data at 400 MeV confirm older measurements; no previous data at 450 MeV have been reported. A comparison of these data with theoretical predictions of Niskanen reveals generally good agreement, although the data tend to exhibit slightly greater asymmetry about 90° than predicted by theory.

NUCLEAR REACTIONS $\vec{p} p \to d π^{+}$ , polarized protons, $T_{p} = 400 and 450$ MeV; measured $A_{y} (θ)$ .

Spin correlation $A_{nn}$ and analyzing power $A$ in $pp \to pp$ at 643 MeV

M. W. McNaughton, E. P. Chamberlin, J. J. Jarmer, N. S. P. King, H. B. Willard, and E. Winkelman

Phys. Rev. C 25, 2107 (1982) - Published 1 April, 1982

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The spin correlation parameter $A_{nn}$ and the analyzing power $A$ have been measured at 643 MeV from 35 to 90° c.m., with statistical uncertainties of ±0.01 to ±0.02 and normalization uncertainty of ±2%. The data are in fair agreement with phase shift predictions and with the trend of most previous data near this energy.

NUCLEAR REACTIONS ${}^{1}H$ ( $p$ , $p$ ) ${}^{1}H$ , $E = 643$ MeV; measured $A_{nn} (θ)$ , $A (θ)$ ; $θ = 35 to 90 °$ c.m.

Polarized neutron capture on ${}^{3}{He}$ at $E_{n} = 9.0$ MeV

H. R. Weller, N. R. Roberson, G. Mitev, L. Ward, and D. R. Tilley

Phys. Rev. C 25, 2111 (1982) - Published 1 April, 1982

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A polarized neutron beam has been used to measure the angular distribution of the analyzing power for the ${}^{3}{He}$ ( $\vec{n}$ , $γ$ ) ${}^{4}{He}$ reaction at $E_{n}$ $(E_{x}) = 9.0 (27.3)$ MeV. The angular distribution of the cross section, obtained with an unpolarized beam, is combined with these data to obtain the $b_{k}$ coefficients. These coefficients are compared to the results of a previous measurement performed for the ${}^{3}H$ ( $\vec{p}$ , $γ$ ) ${}^{4}{He}$ reaction, and to the results of a recent continuum shell model calculation.

NUCLEAR REACTIONS ${}^{3}{He}$ ( $\vec{n}$ , $γ$ ) ${}^{4}{He}$ , measured $σ (θ)$ and $A (θ)$ at $E_{n} = 9.0$ MeV. Compared results to previous ${}^{3}H$ ( $\vec{p}$ , $γ$ ) ${}^{4}{He}$ measurements and to recent continuum shell model calculations.

Investigation of the nuclear continuum by ${}^{40}{Ca}$ inelastic scattering on ${}^{40}{Ca}$ at 160 MeV

Y. Blumenfeld, N. Frascaria, J. P. Garron, J. C. Jacmart, J. C. Roynette, D. Ardouin, and M. Lattuada

Phys. Rev. C 25, 2116 (1982) - Published 1 April, 1982

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The ${}^{40}{Ca}$ + ${}^{40}{Ca}$ reaction has been studied at 160 MeV incident energy. Low lying peaks are observed in the inelastic channel together with a broad bump at 26 MeV total excitation energy. A comparison is made with results obtained in the same reaction at higher bombarding energy.

NUCLEAR REACTIONS ${}^{40}{Ca} + {}^{40}{Ca} - E_{inc} = 160$ MeV; measured $σ (θ, E)$ ; angular range 6° to 40°; compared to higher energy results.

Anomalous $M 4$ conversion coefficient in ${}_{52}^{125}{Te}^{m}$

P. Mukherjee, S. Bhattacharya, S. Sarkar, I. Mukherjee, and B. K. Dasmahapatra

Phys. Rev. C 25, 2120 (1982) - Published 1 April, 1982

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The absolute $M 4$ $K$ -conversion coefficient of the 109.3 keV transition in ${}_{52}^{125}{Te}^{m}$ decay is measured using $K$ -x-ray gamma ray summing in a Ge(Li) x-ray detector. The measured $K$ conversion coefficient is 10% lower than the theoretical value.

RADIOACTIVITY ${}^{125}{Te}^{m}$ , chemical separation, Ge(Li) x-ray detector, measured $α_{K}$ and $α_{T}$ of 35.5 and 109.3 keV transitions.

Role of configuration mixing on absolute alpha-decay width in Po isotopes

F. A. Janouch and R. J. Liotta

Phys. Rev. C 25, 2123 (1982) - Published 1 April, 1982

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Absolute alpha-decay widths for the alpha decays of ${}^{210, 212, 214, 216}{Po}$ are calculated within the framework of the nuclear field theory. A tremendous enhancement factor produced by configuration mixing is found.

RADIOACTIVITY $α$ decay, absolute width in ${}^{210 - 216}{Po}$ ground to ground state calculated by nuclear field theory. Configuration mixing.

Shape isomeric band in ${}^{32}S$

H. Schultheis and R. Schultheis

Phys. Rev. C 25, 2126 (1982) - Published 1 April, 1982

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An unconstrained variation after angular momentum projection yields a rotational shape isomeric band in ${}^{32}S$ . The 8.507, 9.065, 10.276 MeV levels of ${}^{32}S$ are identified as the $0^{+}$ , $2^{+}$ , $4^{+}$ members of the band. Any other set of three known levels (with at least approximate spin assignments) can be ruled out.

NUCLEAR STRUCTURE ${}^{32}S$ ; calculated shape isomeric band, moment of inertia. Variation after projection. Finite-range forces. Experimental levels assigned.

Comment on "Giant $M 1$ states in Zr isotopes within the simple shell model"

T. N. Taddeucci, J. Rapaport, and C. D. Goodman

Phys. Rev. C 25, 2130 (1982) - Published 1 April, 1982

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The quenching factor for $M 1$ strength in the Zr isotopes recently deduced by Toki, Cha, and Bertsch is shown to be based on a false assumption concerning the energy dependence of optical-model distortion effects. When the correct energy dependence is accounted for the previously deduced quenching is increased by a factor of about 2.

NUCLEAR REACTIONS ${}^{90}{Zr}$ ( $p$ , $n$ ), ( $p$ , $p^{'}$ ) differential cross section energy dependence. Deduced $M 1$ quenching factors.

Definitions of the off-shell relative momentum in relativistic theories

David R. Giebink

Phys. Rev. C 25, 2133 (1982) - Published 1 April, 1982

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A variety of definitions of the relative momentum in off-shell systems are discussed and a set of basic requirements for these momenta are established. The off-mass-shell Wightman-Gårding four-momentum, which has been employed most recently by Morioka and Afnan, is shown to be ambiguously defined, and it is shown that the relative four-momentum that is suggested by the magic-vector prescription of Aaron, Amado, and Young should not be used in off-mass-shell systems because it and the total four-momentum do not constitute a complete set of variables for the two-body system.

NUCLEAR REACTIONS Relativistic kinematics, relative momentum, Bethe-Salpeter equation, Blankenbecler-Sugar reductions.

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Composite particle production in high-energy reactions and size of production source

Heavy fragment production through electropion excitation of ${}^{56}{Fe}$

Spectroscopy of gamma rays from ${}^{78}{As}$ decay

Excited $0^{+}$ states and electric monopole transitions in ${}^{118}{Sn}$

Interacting-boson-approximation $E 2$ operator in deformed nuclei

Electromagnetic sum rules by spectral distribution methods

Structure of $N = 85$ nuclei within the cluster-phonon coupling model

Systematics of $E 2$ transition strengths in the Zn—Kr region

Irreversible dynamics of quasispin systems

Photoactivation of ${}^{111}{Cd}$

Excitation of the 10.212 MeV $1^{+}$ state in ${}^{48}{Ca}$ ( $p$ , $p^{'}$ ) at $E_{p} = 44.4$ MeV

Analyzing power of the $\vec{p} p \to π^{+} d$ reaction at 400 and 450 MeV

Spin correlation $A_{nn}$ and analyzing power $A$ in $pp \to pp$ at 643 MeV

Polarized neutron capture on ${}^{3}{He}$ at $E_{n} = 9.0$ MeV

Investigation of the nuclear continuum by ${}^{40}{Ca}$ inelastic scattering on ${}^{40}{Ca}$ at 160 MeV

Anomalous $M 4$ conversion coefficient in ${}_{52}^{125}{Te}^{m}$

Role of configuration mixing on absolute alpha-decay width in Po isotopes

Shape isomeric band in ${}^{32}S$

Comment on "Giant $M 1$ states in Zr isotopes within the simple shell model"

Definitions of the off-shell relative momentum in relativistic theories

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