Recent Articles

$M 2$ transitions between the $1 f_{\frac{7}{2}}$ and the $1 d_{\frac{3}{2}}$ orbit

J. Keinonen, R. Rascher, M. Uhrmacher, N. Wüst, and K. P. Lieb

Phys. Rev. C 14, 160 (1976) - Published 1 July, 1976

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States in ${}^{35, 36}{Cl}$ , ${}^{40}K$ , and ${}^{41}{Ca}$ decaying predominantly by $M 2$ transitions were excited in oxygen induced fusion-evaporation reactions. Their lifetimes were determined by means of the recoil distance Doppler shift technique. A survey on $M 2$ transitions between the $1 f_{\frac{7}{2}}$ and the $1 d_{\frac{3}{2}}$ shell in $33 \leq A \leq 47$ nuclei is presented and the retardations of these transition strengths are discussed. A correlation between the reduced $M 2$ matrix elements and the transition energies has been established.

NUCLEAR REACTIONS ${}^{25}{Mg}$ , ${}^{27}{Al} ({}^{16}O, xy γ)$ , 30-50 MeV; measured $E_{γ}$ , $I_{γ}$ , recoil distance Doppler shift. ${}^{36}{Cl}$ deduced branching ratio, ${}^{35, 36}{Cl}$ , ${}^{40}K$ , ${}^{41}{Ca}$ deduced $T_{\frac{1}{2}}$ . Enriched target.

Spins and lifetimes of yrast states in ${}^{40}{Ca}$

A. M. Nathan and J. J. Kolata

Phys. Rev. C 14, 171 (1976) - Published 1 July, 1976

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The yrast cascade in ${}^{40}{Ca}$ has been studied using the ${}^{28}{Si} ({}^{14}N, p n) {}^{40}{Ca}$ reaction at 36 MeV bombarding energy. The mean lives of two previously reported states at 6931 and 8099 keV excitation have been measured and found to be ${0.49}_{- 0.25}^{+ 0.13}$ and 18.1 ± 2.5 ps, respectively. Angular correlation experiments have been performed to confirm the spin-parity assignments of $6^{+}$ and $8^{+}$ , respectively. On the basis of the present lifetime measurements, the $6^{+}$ state is believed to belong to the 4p-4h deformed band, but the structure of the $8^{+}$ state is uncertain. No evidence is found for a $10^{+}$ level below 11 MeV.

NUCLEAR REACTIONS ${}^{28}{Si} ({}^{14}N, p n γ)$ , $E = 36$ MeV; measured $γ$ - $γ$ coin, $γ γ (θ)$ , $n γ (θ)$ , $T_{\frac{1}{2}}$ ; $γ$ transitions deduced $Λ$ ; ${}^{40}{Ca}$ deduced yrast levels, $J^{π}$ , $B (E 2)$ .

Pole in $k cot δ$ for doublet, $s$ -wave, $n$ - $d$ scattering

James S. Whiting and Michael G. Fuda

Phys. Rev. C 14, 18 (1976) - Published 1 July, 1976

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The position of the pole in $k cot δ$ , for doublet, $s$ -wave, $n$ - $d$ scattering, and its residue are shown to be correlated with the doublet scattering length. An approximate, analytic solution of the $\frac{N}{D}$ equations of Barton and Phillips indicates a linear dependence on the doublet scattering length for the pole position, and a quadratic dependence for the residue. These relationships are tested by means of exact numerical solutions of $\frac{N}{D}$ equations and three-particle equations with separable two-particle interactions, and found to be qualitatively correct. The approximate, analytic solution of the $\frac{N}{D}$ equations leads to a formula for $k cot δ$ , which is of the same form as the phenomenological formula used previously by other authors. A formalism is presented which makes it possible to parametrize the effect of the omitted portion of the left hand cut in an $\frac{N}{D}$ calculation.

NUCLEAR REACTIONS Pole in $n$ - $d$ , doublet, $s$ -wave $k cot δ$ , $\frac{N}{D}$ calculations, solutions of three-particle equations with separable interactions.

Charge distribution, neutron evaporation, and energy distribution in higher energy binary fission

D. N. Sharma, M. R. Iyer, and A. K. Ganguly

Phys. Rev. C 14, 181 (1976) - Published 1 July, 1976

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A computational procedure based on the order-disorder model for predicting independent yields of fission products in higher energy fission is described. Based on the experimental observation that increase in excitation energy of the compound nucleus is used up only in exciting the fragments resulting from fission, a scheme for the distribution of extra excitation between the fragments has been evolved. The extra excitation energy is shown to be shared between the two impending fragments in proportion to the number of neutrons out of the balance number (as per the order-disorder model) going to either of the fragments. The calculational procedure essentially consists of making use of the scheme and obtaining the excitation energy of the fragments for higher energy fission from those for spontaneous fission. Data on neutrons evaporated $\bar{ν} (Z_{i}, N_{j})$ from individual fragments for the higher energy fission are calculated from the excitation energy using the cascade evaporation scheme. The product isotopic distributions are calculated from $\bar{ν} (Z_{i}, N_{j})$ data and calculated fragment isotopic distributions given by the order-disorder model. The product isotopic distributions thus calculated along with experimental product mass yield data give the independent yields of the products. The results obtained for fission of ${}^{235}U$ by fission spectrum neutrons (fast) and 14.7 MeV (high energy) neutrons are discussed in the paper. A comparison of the predicted independent yields with experimental values shows good agreement within reasonable limits. The total isotopic yield versus $Z$ distribution for fast and high energy neutronic fission show as expected a decrease in peak to valley ratio with increasing excitation energy of the compound nucleus. $\bar{ν} (Z_{i}, N_{j})$ distributions for both the fission reactions are presented. They show less pronounced shell effects at $N = 50 and 82$ than in the case of thermal fission. The isotopic, isobaric, and isotonic averages of $\bar{ν} (Z_{i}, N_{j})$ retain the sawtooth nature as in the case of thermal fission. The Wahl plot shows that $| Z_{p} - Z_{UCD} |$ decreases with increasing energy of fission. The present study also confirms the experimental observation that $Z_{p}$ for higher energy fission lies between the values predicted by the unchanged charge density and equal charge displacement hypotheses.

NUCLEAR REACTIONS, FISSION ${}^{235}U (n, f)$ , $E = 2$ MeV, 14.7 MeV; calculated isotopic distributions, charge distributions, independent yields of products and neutron evaporation and energy distribution in individual fragments using order-disorder model.

$K^{+}$ and $π^{+}$ momentum spectra from 2.5-3.1 GeV/c protons on carbon and two-body final-state spectral peaks from ( $p, K^{+}$ ) and ( $p, π^{+}$ ) reactions

T. Bowen, D. A. DeLise, and A. E. Pifer

Phys. Rev. C 14, 195 (1976) - Published 1 July, 1976

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A partially separated 0.9-1.8 GeV/c $K^{+}$ beam at the Bevatron was utilized as a spectrometer (0.9% full width at half maximum) to study the $K^{+}$ and $π^{+}$ momentum spectra at 0° from carbon and other target elements bombarded by 2.5-3.1 GeV/c protons. Searches were made for possible spectral peaks resulting from two-body final state reactions such as ${}^{12}C (p, K^{+}) {}^{13}C_{Λ}$ and ${}^{12}C (p, π^{+}) {}^{13}C$ . Spectral peaks observed from $p (p, π^{+}) d$ assisted in calibrating the apparatus, and a spectral structure attributed to $p [p, K^{+}] {(p Λ)}^{*}$ was observed, where ${(p Λ)}^{*}$ represents $p$ and $Λ$ with low relative momentum. No other $K^{+}$ or $π^{+}$ spectral peaks appeared above background; upper limits are given which this experiment places on ${(\frac{d σ}{d Ω})}_{c . m .}$ at 0°. The $K^{+}$ and $π^{+}$ momentum spectra at 0° from carbon bombarded by 2.50, 2.70, 2.89, and 3.10 GeV/c protons are also given.

NUCLEAR REACTIONS Hypernuclei $p (p, K^{+}) {(p Λ)}^{*}$ , $E = 1.9 - 2.3$ GeV; measured $σ (E; θ = 0)$ near maximum $K^{+}$ momentum; results poorly fitted by Goldberger-Watson type calculation of $p$ - $Λ$ final state interaction. ${}^{12}C (p, K^{+})$ , ${}^{12}C (p, π^{+})$ , $E = 1.7 - 2.3$ GeV; measured $σ (E; θ = 0, P)$ . ${}^{12}C (p, π^{+}) {}^{13}C$ , ${}^{12}C (p, K^{+}) {}^{13}C_{Λ}$ , ${}^{9}{Be} (p, K^{+}) {}^{10}{Be}_{Λ}$ , ${}^{56}{Fe} (p, K^{+}) {}^{57}{Fe}_{Λ}$ , $E = 1.7$ GeV; $d (p, K^{+}) {}^{3}H_{Λ}$ , $E = 1.9$ GeV; ${}^{12}C (p, K^{+}) {}^{13}C$ , $E = 1.9, 2.1$ GeV; searched and set upper limits on $σ (E; θ = 0)$ ; deduced qualitative upper limit to high momentum components of $Λ$ in ${}^{13}C_{Λ}$ .

Comparison of field theoretic and potential inverse problems in pion-nucleus scattering

Robert A. Friedenberg and Douglas L. Weiss

Phys. Rev. C 14, 204 (1976) - Published 1 July, 1976

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The elastic scattering of $π^{+}$ on ${}^{12}C$ in the $P 33$ channel is examined for two different two-body interaction theories. A modified Chew-Low interaction and an energy dependent separable potential, both of which are solved as inverse problems to fit the on-shell two-body data exactly, are used to construct a first order optical potential. Differential cross sections are calculated in the impulse approximation at three energies; below, at, and above the energy of the $π$ -nucleon resonance in the (3,3) channel. The differences between cross sections of the two models are compared to the differences made by varying the high energy phase shifts in the region where they are not well known experimentally ( $E_{c . m .} > 1900$ MeV) and found to be of the same order of magnitude.

NUCLEAR REACTIONS ${}^{12}C (π, π)$ , $E = 75, 150, 250$ MeV; calculated $σ (θ)$ with potential and field theoretic model of $π$ -nucleon interaction.

Decay properties of neutron-rich niobium isotopes

H. Ahrens, N. Kaffrell, N. Trautmann, and G. Herrmann

Phys. Rev. C 14, 211 (1976) - Published 1 July, 1976

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The decay of neutron-rich niobium isotopes in the mass region $A ≃ 100$ has been investigated by $γ$ -ray singles and $γ$ - $γ$ coincidence measurements. The isotopes were produced by thermal-neutron induced fission of ${}^{235}U$ , ${}^{239}{Pu}$ , and ${}^{249}{Cf}$ , and niobium was separated from fission-product mixtures with an automated chemical procedure. Isomerism was found in the even-mass niobium isotopes with the following half-lives: 1.5 and 3.1 sec for ${}^{100}{Nb}$ , 1.3 and 4.3 sec for ${}^{102}{Nb}$ , and 0.8 and 4.8 sec for ${}^{104}{Nb}$ . Half-lives and $γ$ rays were assigned to the 15.0-sec ${}^{99}{Nb}$ , 7.1-sec ${}^{101}{Nb}$ , 1.5-sec ${}^{103}{Nb}$ , and ∼1-sec ${}^{106}{Nb}$ . Revised half-life values are given for the 7.1-sec ${}^{100}{Zr}$ and 2.9-sec ${}^{102}{Zr}$ . RADIOACTIVITY ${}^{99, 100, 101, 102, 103, 104, 106}{Nb}$ , ${}^{100, 102}{Zr}$ ; measured $T_{\frac{1}{2}}$ , $E_{γ}$ , $γ$ - $γ$ -coin. ${}^{100, 102, 104}{Mo}$ deduced levels. Fission ${}^{235}U$ , ${}^{239}{Pu}$ , ${}^{249}{Cf} (n_{th}, f)$ ; automated chemical separation procedure, Ge(Li) detectors.

One- and three-quasiparticle states in ${}^{249}{Cf}$ populated by the electron capture decay of 1.70-h ${}^{249}{Es}$

I. Ahmad, R. K. Sjoblom, and P. R. Fields

Phys. Rev. C 14, 218 (1976) - Published 1 July, 1976

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The level structure of ${}^{249}{Cf}$ has been investigated by measuring the $γ$ rays and conversion electrons associated with the electron capture decay of 1.70-h ${}^{249}{Es}$ . The $γ$ -ray spectra were measured with a 2- ${cm}^{2}$ ×5-mm planar and a 25- ${cm}^{3}$ coaxial Ge(Li) detector and the conversion-electron spectra were measured with a cooled Si(Li) detector. Forty-six $γ$ rays were identified and multipolarities of most of the transitions were deduced. The half-life of ${}^{249}{Es}$ was determined from the decay rate of the 379.5-keV photopeak and was found to be 102.2 ± 0.6 min. The $log ft$ values for the observed electron capture transitions were derived from the measured electron capture intensities. On the basis of the present work the following intrinsic states were identified: $\frac{9}{2} - [734]$ , 0; $\frac{5}{2} + [622]$ , 145.0; $\frac{7}{2} + [624]$ , 379.5; $\frac{7}{2} + [613]$ , 443.0; $K π = \frac{5}{2} -$ , 813.2; $\frac{9}{2} + [615]$ , 1007.9; and $K π = \frac{7}{2} -$ , 1218.5. The $\frac{5}{2} -$ band at 813.2 keV has been interpreted as the $γ$ -vibrational band coupled to the $\frac{9}{2} - [734]$ ground state. The $\frac{7}{2} -$ state at 1218.5 keV has been interpreted as a three-quasiparticle state with configuration ${p [633] \frac{7}{2} +; p [521] \frac{3}{2} -; n [622] \frac{3}{2} +}_{\frac{7}{2} -}$ . This is the first time a three-quasiparticle state in an actinide nucleus has been identified. An enhancement in the $B (E 3)$ value of the 145.0→ 0 transition has been observed which suggests collective admixture in the 145.0-keV state. From the experimental $B (E 3)$ value the admixture (amplitude squared) of the ${\frac{9}{2} - [734] \otimes 2^{-}}_{\frac{5}{2} +}$ configuration in the 145.0-keV state has been derived to be ∼ 29%, in excellent agreement with the results of ( $d, d^{'}$ ) reaction studies.

RADIOACTIVITY ${}^{249}{Es}$ [from ${}^{249}{Cf} (d, 2 n)$ and ${}^{249}{Bk} (α, 4 n)$ ]; measured $T_{\frac{1}{2}}$ , $E_{γ}$ , $I_{γ}$ , $E_{ce}$ , $I_{ce}$ . ${}^{249}{Cf}$ deduced levels, $log ft (EC)$ , $γ$ multipolarity, $I$ , $π$ , 5 single-particle states, one vibrational state, one three-quasiparticle state. Mass-separated ${}^{249}{Es}$ .

Decay of ${}^{111, 112, 113, 114, 115}{Sb}$

M. E. J. Wigmans, R. J. Heynis, P. M. A. van der Kam, and H. Verheul

Phys. Rev. C 14, 229 (1976) - Published 1 July, 1976

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The decay of the isotopes ${}^{111}{Sb}$ ( $T_{\frac{1}{2}} = 75.5$ sec), ${}^{112}{Sb}$ ( $T_{\frac{1}{2}} = 51.4$ sec), ${}^{113}{Sb}$ ( $T_{\frac{1}{2}} = 6.67$ min), ${}^{114}{Sb}$ ( $T_{\frac{1}{2}} = 3.51$ min), and ${}^{115}{Sb}$ ( $T_{\frac{1}{2}} = 32.1$ min) is investigated. Decay schemes are proposed and compared to previously available data and theoretical calculations. Some systematic trends are discussed.

RADIO ACTIVITY ${}^{111, 112, 113, 114, 115}{Sb}$ [from ${}^{(112), (114)}{Sn} (p, xn or d, n)$ ]; measured $T_{\frac{1}{2}}$ , $E_{γ}$ , $γ γ$ coin; deduced $log ft$ , ${}^{111, 112, 113, 114, 115}{Sn}$ deduced levels, $J$ , $π$ . Enriched targets, mass separated sources.

Study of the $α + {}^{16}O$ system with the resonating-group method

M. LeMere, Y. C. Tang, and D. R. Thompson

Phys. Rev. C 14, 23 (1976) - Published 1 July, 1976

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The resonating-group method is used to study the $α + {}^{16}O$ system. The cluster internal functions used are translationally invariant antisymmetrized products of single-particle wave functions of the lowest configuration in harmonic-oscillator wells, with width parameters chosen to yield the correct rms radii of both the $α$ and the ${}^{16}O$ clusters. A generator-coordinate technique is employed to derive the integrodifferential equation which governs the relative motion between the clusters. The result shows that a fairly satisfactory description of the ${}^{20}{Ne}$ rotational bands can be obtained. In addition, it is found that, with the introduction of a phenomenological imaginary potential to take reaction effects into account, the calculation also yields differential scattering cross sections which agree rather well with experimental data.

[NUCLEAR REACTIONS ${}^{16}O (α, α)$ ; calculated phase shifts and $σ (θ)$ . Resonating-group method with generator-coordinate technique.]

Decay of ${}^{112, 113, 114}{Te}$ and ${}^{115}{Te}^{g + m}$

M. E. J. Wigmans, R. J. Heynis, P. M. A. van der Kam, and H. Verheul

Phys. Rev. C 14, 243 (1976) - Published 1 July, 1976

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The decay of the two new isotopes ${}^{112}{Te}$ ( $T_{\frac{1}{2}} = 2.0 \pm 0.2$ min) and ${}^{113}{Te}$ ( $T_{\frac{1}{2}} = 1.6 \pm 0.2$ min) is investigated, together with the decay of the ${}^{114}{Te}$ ( $T_{\frac{1}{2}} = 15.2 \pm 0.7$ min) and the two isomers in ${}^{115}{Te}$ ( $T_{\frac{1}{2}} = 5.7 \pm 0.2 min and 6.7 \pm 0.4 min$ ). Decay schemes are proposed and compared to previously available data and theoretical calculations. Some systematic trends are discussed.

RADIOACTIVITY ${}^{112, 113, 114}{Te}$ , ${}^{115}{Te}^{g + m}$ [from ${}^{(112), (114)}{Sn} ({}^{3}{He}, x n)$ )]; measured $T_{\frac{1}{2}}$ , $E_{γ}$ , $γ γ$ -coin, $γ γ Δ t$ ; deduced $log ft$ ; ${}^{112, 113, 114, 115}{Sb}$ deduced levels, $J$ , $π$ . Isotope separated sources.

Decay of ${}^{20}{Na}$ to $γ$ -ray emitting states of ${}^{20}{Ne}$

P. D. Ingalls

Phys. Rev. C 14, 254 (1976) - Published 1 July, 1976

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${}^{20}{Ne}$ $γ$ rays following ${}^{20}{Na}$ decay identified new branches to states at 9.87, 10.88, and 11.26 MeV, as well as known branches to states at 1.63 and 10.27 MeV. Branching ratios and $F t$ values based on these observations are compared to nuclear structure calculations, and the $β^{\pm}$ $F t$ asymmetry for $A = 20$ is discussed.

RADIOACTIVITY ${}^{20}{Na}$ [from ${}^{20}{Ne} (p, n)$ , $E = 22.9$ MeV]; measured $E_{γ}$ , $I_{γ}$ ; deduced $β^{+}$ branching ratios, $F t$ values, ${}^{20}{Ne}$ levels $J^{π}$ , mirror $β^{+}$ asymmetry; enriched target; Ge(Li) detector.

Weak gamma rays observed in the ${}^{60}{Co}$ decay

D. C. Camp and J. R. Van Hise

Phys. Rev. C 14, 261 (1976) - Published 1 July, 1976

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The intensities and energies of the 346.93-, 826.28-, and 2158.77-keV transitions, and intensity limits for the 467.4- and 1293.7-keV transitions in the decay of ${}^{60}{Co}$ were measured using a new improved Compton suppression spectrometer. The spectrometer yields a maximum Compton continuum suppression of 28 and a peak-to-minimum Compton ratio of 550/1 for the 1332.5-keV transition of ${}^{60}{Co}$ .

RADIOACTIVITY ${}^{60}{Co}$ [from ${}^{59}{Co} (n, γ)$ ]; measured $E_{γ}$ , $I_{γ}$ ; deduced $log ft$ . ${}^{60}{Ni}$ deduced energy levels. Compton suppression spectrometer.

$α$ decay of ${}^{186}{Tl}$

M. A. Ijaz, J. Lin, E. L. Robinson, and K. S. Toth

Phys. Rev. C 14, 264 (1976) - Published 1 July, 1976

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$α$ decay for thallium isotopes has never been clearly established. In this study thallium and mercury nuclides were produced by ( ${}^{14}N$ , $xn$ and $pxn$ ) reactions induced by 168-MeV ${}^{14}N$ bombardments of ${}^{182}W$ and investigated using an on-line mass-separator facility. $α$ -particle and $γ$ - and x-ray spectral measurements were made simultaneously. At $A = 186$ a new $α$ peak was observed with $E_{α} = 5.641 \pm 0.010$ MeV; we assign it to 28-sec ${}^{186}{T 1}$ . By assuming the 405.3-keV ( $2^{+}$ → $0^{+}$ ) transition to encompass the ${\frac{EC}{β}}^{+}$ decay of 28-sec ${}^{186}{T 1}$ its $α$ -decay branch was determined to be (6 ± 2) × $10^{- 4}$ . Measurements at $A = 184$ and $A = 185$ revealed no $α$ groups that could be assigned with any certainty to ${}^{184, 185}{T 1}$ . The measurements did, however, corroborate the $α$ -decay energies and total half-lives for ${}^{183 - 185}{Hg}$ as reported by P. G. Hansen et al.

RADIOACTIVITY ${}^{186}{T 1}$ ; $T_{\frac{1}{2}}$ , $E_{α}$ , $I_{α}$ , $E_{γ}$ , $I_{γ}$ ; measured α-decay branching ratio. ${}^{183, 184, 185, 186}{Hg}$ ; $T_{\frac{1}{2}}$ , $E_{α}$ .

Experimental and theoretical multipole mixing ratios in transitions of ${}^{208}{Ph}$

F. T. Avignone, III, S. M. Blankenship, and William W. True

Phys. Rev. C 14, 267 (1976) - Published 1 July, 1976

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$γ$ - $γ$ directional correlations of the 277-583, 511-583, 722-583, 763-583, and 861-2615 keV cascades have been measured. The data support the spin and parity assignments of $(J π) = (6 -) and (5 -)$ to the 3920 and 3961 keV levels, respectively. The following experimental multipole mixing ratios were extracted from the data: $δ (277) = + 0.0080 \pm 0.011$ , $δ (511) = - 0.052 \pm 0.045 or - 0.68 \pm 0.08$ , $δ (722) = + 0.31 \pm 0.07$ , $δ (763) = - 0.01 \pm 0.06$ , and $δ (861) = + 0.015 \pm 0.012$ . These mixing ratios were also calculated in the framework of the particle-hole model with the following results: $δ (277) = + 0.0098$ , $δ (511) = + 0.0196$ , $δ (722) = + 0.1915$ , $δ (763) = - 0.0653 or + 0.0219$ , and $δ (861) = + 0.0154$ . The two possible values of $δ (763)$ correspond to the two theoretically predicted (5-) states at 4.00 and 4.18 MeV, respectively.

RADIOACTIVITY ${}^{228}{Th}$ ; measured $γ γ (θ)$ ; deduced $δ$ for $γ$ rays in ${}^{208}{Pb}$ . NUCLEAR STRUCTURE ${}^{208}{Pb}$ ; calculated $δ$ for same $γ$ rays in ${}^{208}{Pb}$ . Particlehole model.

Decay of mass-separated ${}^{138}I$

W. R. Western, John C. Hill, W. C. Schick, Jr.,, and W. L. Talbert, Jr.

Phys. Rev. C 14, 275 (1976) - Published 1 July, 1976

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The $γ$ rays following the $β$ decay of mass-separated ${}^{138}I$ to levels in ${}^{138}{Xe}$ have been measured using Ge(Li) detectors for both singles and coincidence spectra. A level scheme of ${}^{138}{Xe}$ has been constructed in which eight transitions are placed between levels at 589, 1073, 1464, 1867, 1903, and 2398 keV. The implications of this study are discussed for the systematics of even-even Xe isotopes and $N = 84$ isotones.

RADIOACTIVITY ${}^{138}I$ [from ${}^{235}U (n, f)$ ]; measured $E_{γ}$ , $I_{γ}$ , $γ γ$ -coin. Ge(Li) detectors; ${}^{138}{Xe}$ deduced levels, $J$ , $π$ , $log ft$ . Mass-separated ${}^{138}I$ activity.

Giant $E 1$ resonances in ${}^{8}{Be}$ from the reaction ${}^{7}{Li} (p, γ) {}^{8}{Be}$

G. A. Fisher, P. Paul, F. Riess, and S. S. Hanna

Phys. Rev. C 14, 28 (1976) - Published 1 July, 1976

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The giant electric dipole resonances based on the ground state ( $0^{+}$ ) and first excited state ( $2^{+}$ ) of ${}^{8}{Be}$ have been studied with the reactions ${}^{7}{Li} (p, γ_{0}) {}^{8}{Be}$ and ${}^{7}{Li} (p, γ_{1}) {}^{8}{Be}$ over the range $E_{p} = 0.8 to 17.6$ MeV. Both resonances show a simple resonant shape with little fine structure. The $γ_{1}$ giant resonance is displaced upward from the $γ_{0}$ resonance by an energy of 2.2 MeV which is approximately equal to the excitation of the $2^{+}$ state. The reduced ( $γ, p_{0}$ ) strengths of the two resonances are approximately equal and each exhausts about 10% of the $E 1$ sum rule. The angular distributions for both $γ_{0}$ and $γ_{1}$ are quite constant over the giant resonance structure and are predominantly dipole in character. A simple model can be invoked to explain the dominant $E 1$ features. The presence of $P_{1} (cos θ)$ and $P_{3} (cos θ)$ terms in both angular distributions indicates $E 2$ strength which probably increases above the $E 1$ resonances. Some parameters for the narrow levels at 18.15 and 19.06 MeV in ${}^{8}{Be}$ are given.

NUCLEAR REACTIONS ${}^{7}{Li} (p, γ)$ , $E = 0.8 - 17.6$ MeV; measured $σ (E; E_{γ}, θ)$ . Deduced properties ${}^{8}{Be}$ levels at $E_{x} = 18.15, 19.06$ MeV and $γ_{0}$ , $γ_{1}$ giant resonances. 99% enriched ${}^{7}{Li}$ target.

$K$ -shell internal-ionization probabilities in nuclear $β^{-}$ decay

H. H. Hansen

Phys. Rev. C 14, 281 (1976) - Published 1 July, 1976

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Total $K$ -shell internal-ionization probabilities per $β^{-}$ decay of the isotopes ${}^{63}{Ni}$ , ${}^{143}\Pr$ , and ${}^{204}{Tl}$ have been determined by x-ray spectroscopy with a high-energy-resolution Si(Li) detector. The number of emitted $K$ x rays was deduced in comparison to the absolute $β^{-}$ -decay rate. The results of (4.6 ± 0.4) × $10^{- 4}$ for ${}^{63}{Ni}$ , (2.92 ± 0.16) × $10^{- 4}$ for ${}^{143}\Pr$ , and (1.12 ± 0.11) × $10^{- 4}$ for ${}^{204}{Tl}$ are compared with previous experimental values and recent theoretical calculations of Law and Campbell. Good agreement is found between this theory and the present experimental results.

RADIOACTIVITY $β^{-}$ emitters ${}^{63}{Ni}$ , ${}^{143}\Pr$ , and ${}^{204}{Tl}$ ; measured $K$ -shell internalionization probabilities. Si(Li) x-ray detector 260 eV at 5.9 keV.

Calculation of the $Λ$ -particle binding energy in nuclear matter with a simple functional variation method

S. Ali, M. E. Grypeos, and B. Kargas

Phys. Rev. C 14, 285 (1976) - Published 1 July, 1976

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Results of calculations based on a first order functional variation method for the binding energy $D$ of a $Λ$ particle in infinite nuclear matter are reported. Some additional details of the formal part of the problem which had been previously discussed are also given. In particular, the "stability condition" is studied and the analytic solution in the case of the exponential with hard core potentials is also derived. Various nucleon-nucleon correlation functions and central $Λ$ -nucleon potentials are used in order to investigate the dependence of $D$ on them. The results, which are obtained by including in the computations the second order terms (in the density $ρ$ of nuclear matter) show, for some potentials, large overbinding of the $Λ$ particle, while for other potentials the overbinding is considerably reduced. A discussion of the results is finally made.

NUCLEAR STRUCTURE Binding energy of $Λ$ particle, $Λ$ -nucleon interaction.

High-spin states in Pd isotopes and gapless superconductivity

M. K. Ghosh and S. R. Majumdar

Phys. Rev. C 14, 298 (1976) - Published 1 July, 1976

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High-spin states in the fast rotating nuclei are investigated. At first, an exact matrix diagonalization of Nilsson and the Coriolis force Hamiltonian is done for high values of the angular velocity $ω$ . The weak pairing correlation in the rotating frame is taken into account using a perturbation method and employing the newly obtained basis function after matrix diagonalization. Numerical calculations are performed for Pd isotopes and the possibility of gapless excitations in some cases is discussed.

NUCLEAR STRUCTURE ${}^{100 - 102}{Pd}$ , calculated energy, neutron orbital; Nilsson plus Coriolis force Hamiltonian. ${}^{100 - 102}{Pd}$ , calculated $Δ$ ; perturbation approximation, pairing interaction.

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$M 2$ transitions between the $1 f_{\frac{7}{2}}$ and the $1 d_{\frac{3}{2}}$ orbit

Spins and lifetimes of yrast states in ${}^{40}{Ca}$

Pole in $k cot δ$ for doublet, $s$ -wave, $n$ - $d$ scattering

Charge distribution, neutron evaporation, and energy distribution in higher energy binary fission

$K^{+}$ and $π^{+}$ momentum spectra from 2.5-3.1 GeV/c protons on carbon and two-body final-state spectral peaks from ( $p, K^{+}$ ) and ( $p, π^{+}$ ) reactions

Comparison of field theoretic and potential inverse problems in pion-nucleus scattering

Decay properties of neutron-rich niobium isotopes

One- and three-quasiparticle states in ${}^{249}{Cf}$ populated by the electron capture decay of 1.70-h ${}^{249}{Es}$

Decay of ${}^{111, 112, 113, 114, 115}{Sb}$

Study of the $α + {}^{16}O$ system with the resonating-group method

Decay of ${}^{112, 113, 114}{Te}$ and ${}^{115}{Te}^{g + m}$

Decay of ${}^{20}{Na}$ to $γ$ -ray emitting states of ${}^{20}{Ne}$

Weak gamma rays observed in the ${}^{60}{Co}$ decay

$α$ decay of ${}^{186}{Tl}$

Experimental and theoretical multipole mixing ratios in transitions of ${}^{208}{Ph}$

Decay of mass-separated ${}^{138}I$

Giant $E 1$ resonances in ${}^{8}{Be}$ from the reaction ${}^{7}{Li} (p, γ) {}^{8}{Be}$

$K$ -shell internal-ionization probabilities in nuclear $β^{-}$ decay

Calculation of the $Λ$ -particle binding energy in nuclear matter with a simple functional variation method

High-spin states in Pd isotopes and gapless superconductivity

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