Recent Articles

RAPID COMMUNICATION

$g$ factor of the 635.4 keV level in ${}^{171}{Tm}$

S. B. Patel, P. P. Tandon, and K. P. Gopinathan

Phys. Rev. C 14, 2027(R) (1976) - Published 1 November, 1976

Show Abstract

The $g$ factor of the 635.4 keV level in ${}^{171}{Tm}$ , fed in the $β^{-}$ decay of 7.5 h ${}^{171}{Er}$ , has been measured using perturbed angular correlation technique. The 277.4-210.5 keV $γ - γ$ cascade through this level was employed for the measurements. The mean precession angle $ω τ$ for this level in an external field of 10 kG was measured to be $G_{2} ω τ = 0.232 \pm 0.031$ rad; $G_{2}$ was estimated to be $G_{2} = 0.85 \pm 0.05$ . Using the known value of the half-life for this level, $T_{\frac{1}{2}} = 1.26 \pm 0.06$ nsec, the $g$ factor is found to be $g = + (0.62 \pm 0.09)$ . The measured value of the $g$ factor for this level is in agreement with the earlier assignment of this state to be the $[404] {\frac{7}{2}}^{+}$ Nilsson state.

[RADIOACTIVITY ${}^{171}{Er}$ from ${}^{170}{Er} (n, γ)$ , measured $γ γ (θ)$ , $γ γ (θ, H)$ . ${}^{171}{Tm}$ levels, deduced $g$ , $μ$ . Enriched target.]

Bounds on the rate of ${}^{1}H (p, e^{+} ν) {}^{2}H$ in impulse approximation

H. S. Picker and M. I. Haftel

Phys. Rev. C 14, 1293 (1976) - Published 1 October, 1976

Show Abstract

Working in impulse approximation, we derive simple bounds on the experimentally inaccessible rate of the proton-proton reaction ${}^{1}H (p, e^{+} ν) {}^{2}H$ , using only a few common and physically plausible assumptions. We evaluate these bounds at the kilovolt energies of interest for hydrogen burning in stars and find that they permit at most a few percent enhancement over currently accepted impulse-approximation rates. Within the framework of the usual nonrelativistic Schrödinger-equation description of the two-nucleon interaction, this result is obtained independent of the specific features of the two-nucleon interaction at distances less than 3 fm, provided that the energy dependence of the interaction may be neglected at the low energies in question.

NUCLEAR REACTIONS ${}^{1}H (p, e^{+} ν)$ ; bounds on rate in impulse approximation, keV energies, arbitrary energy-independent short-range two-nucleon interaction.

Upper limit for the ${}^{1}H (n, γ γ) {}^{2}H$ cross section

E. D. Earle, A. B. McDonald, and M. A. Lone

Phys. Rev. C 14, 1298 (1976) - Published 1 October, 1976

Show Abstract

A value of (- 0.8 ± 2.5) × $10^{- 5}$ has been measured for the ratio of double-photon to single-photon emission following neutron capture in hydrogen for $600 keV < E_{γ} < 1620 keV$ . The two Ge(Li) detectors used in the experiment subtended an angle of 85° at the $H_{2}$ O target and were shielded from each other to reduce the background from the cross registration of single $γ$ rays. The upper limit of the measured two-photon cross section (-3 ± 8 μb) is two orders of magnitude larger than the most recent theoretical predictions ( $\approx 0.07$ μb) for this energy range.

NUCLEAR REACTIONS ${}^{3}H (n, γ γ)$ , thermal $n$ , measured $σ_{2 γ}$ Ge(Li) detectors.

Doubly radiative $np$ capture

H. C. Lee and F. C. Khanna

Phys. Rev. C 14, 1306 (1976) - Published 1 October, 1976

Show Abstract

The theory of the reaction $n + p \to d + γ + γ$ is reviewed with emphasis on the dominant, or ( $E 1, E 1$ ), mode. The differences between the length and the gradient electric dipole operators are studied in detail and the two-photon cross section ( $σ_{2 γ}$ ) is calculated using both operators. The length operator yields a very reliable value of $σ_{2 γ} = 0.118$ μb (± 1%). The result obtained with the gradient operator is ∼20% smaller and has large uncertainties. Results for other two-photon modes are also presented.

[NUCLEAR REACTIONS ${}^{1}H (n, γ γ)$ , thermal $n$ , calculated $σ_{2 γ}$ .]

Experimental study of giant dipole and quadrupole resonances in ${}^{16}O$

M. Buenerd, P. Martin, P. de Saintignon, and J. M. Loiseaux

Phys. Rev. C 14, 1316 (1976) - Published 1 October, 1976

Show Abstract

The 20-30 MeV excitation energy region of ${}^{16}O$ was investigated by inelastic scattering of 45 MeV protons and 60 MeV $α$ particles. Both $E 1$ and $E 2$ strengths are present, exhausting, respectively, about 50% and between 16 and 21% of the corresponding energy-weighted sum rule. Microscopic calculations also reproduce angular distributions fairly well.

NUCLEAR REACTIONS ${}^{16}O (p, p^{'})$ , $E_{p} = 45$ MeV, ${}^{16}O (α, α^{'})$ , $E_{α} = 60$ Mev, $E_{x} = 0 - 30$ MeV; measured $σ (E_{x}, θ)$ ; discuss giant resonances.

$γ$ -ray decay of the first $T = 2$ state in ${}^{36}{Ar}$

D. J. Martin, H. C. Evans, and J. A. Szücs

Phys. Rev. C 14, 1320 (1976) - Published 1 October, 1976

Show Abstract

A resonance in the ${}^{35}{Cl} {(p, γ)}^{36} Ar$ reaction at a proton energy of $E_{p} = 2410 \pm 2$ keV has been studied using three Ge(Li) detectors. The resonance at an excitation energy of $E^{*} = 10849.7 \pm 1.5$ keV decays to states at 8129.8 ± 1.4 and 7707.9 ± 1.4 keV with branching ratios of (60.2 ± 4.5)% and (39.8 ± 3.0)%, respectively. The angular distributions of the two primary $γ$ rays are found to be isotropic. The resonance is identified as the lowest $T = 2$ state in ${}^{36}{Ar}$ , and the states at 8130 and 7708 keV are identified as the analogs of the $J^{π}$ , $T = 1^{+}, 1$ levels at 1601 and 1165 keV in ${}^{36}{Cl}$ . The resonance strength was measured and combining the result with a recent measurement of $\frac{Γ_{p}}{Γ}$ leads to an estimate for the total $γ$ -ray width of the $T = 2$ state of $75 meV < Γ_{γ} < 85 meV$ meV. Upper limits for the partial $γ$ -ray width of possible $Δ T = 2$ transitions have been obtained and the significance for isospin mixing of the states in ${}^{36}{Ar}$ and the existence of isotensor electromagnetic currents is discussed. The known $γ$ -ray properties of $T = 2$ states are collected and discussed.

NUCLEAR REACTIONS ${}^{35}{Cl} (p, γ)$ , $E_{p} = 2410 \pm 2$ keV resonance, Measured $σ (E_{p})$ , $σ (E_{γ}, θ)$ , resonance strength. Deduced decay scheme, $Γ_{γ}$ , upper limits for $Δ T = 2$ transitions. Identified lowest $T = 2$ state in ${}^{36}{Ar}$ , analogs of $J^{π}$ , $T = 1^{+}$ states of ${}^{36}{Cl}$ . Enriched target.

Isobaric analog impurities from neutron capture and transmission by magnesium

H. Weigmann, R. L. Macklin, and J. A. Harvey

Phys. Rev. C 14, 1328 (1976) - Published 1 October, 1976

Show Abstract

Resonance neutron interactions with the stable isotopes of magnesium were measured at the Oak Ridge electron linear accelerator time-of-flight facility. The transmission of a natural metal sample (78.7% ${}^{24}{Mg}$ ) was measured at 200 m and capture by natural metal and by enriched isotope samples was measured at 40 m. Twenty-six resonances in ${}^{24}{Mg} + n$ up to 1.8 MeV were fitted with Breit-Wigner multilevel parameters. The data were sufficient to assign spin and parity to 19 of these. The capture data were analyzed for resonances up to 850 keV for ${}^{24}{Mg} + n$ , 265 keV for ${}^{25}{Mg} + n$ ( $17^{+}$ resonances), and 440 keV for ${}^{26}{Mg} + n$ (4 resonances). Average capture at stellar interior temperatures was calculated. The ${}^{24}{Mg} + n$ data serve to assess the isospin impurities in three isobaric analog states. Three other states exhibit reduced neutron widths each several percent of the Wigner limit which may be understood in terms of simple shell model configurations.

NUCLEAR REACTIONS $Mg (n, x) {}^{24, 25, 26}{Mg} (n, γ)$ , $E = 0.1 - 1800$ keV; measured $T (E)$ and $σ_{n, γ} (E)$ ; deduced ${}^{25, 26, 27}{Mg}$ level parameters, isobaric analog isospin impurities, shell model configurations, average capture in stars as a function of temperature.

Two-nucleon exchange cuts in the Amado model for $n - d$ scattering

Michael G. Fuda

Phys. Rev. C 14, 1336 (1976) - Published 1 October, 1976

Show Abstract

A study is carried out of some of the singularities that occur in the second Born amplitude for elastic $n - d$ scattering as described by the Amado model. It is shown that for real energies this amplitude is analytic in the momentum transfer plane except for a right hand cut, and that the discontinuity across the leading edge of the cut depends only on the on-shell, two-nucleon $t$ matrix. This right hand cut leads to a left hand cut in the energy plane for the partial wave amplitudes. A simple formula which involves only the on-shell $t$ matrix is derived for the discontinuity across the leading edge of the $s$ -wave left hand cut. The possible implications of these results for the model dependence of three-nucleon calculations are discussed.

NUCLEAR REACTIONS Cuts in second Born amplitudes for elastic $n - d$ scattering; relation between discontinuities and on-shell, two-nucleon amplitudes.

Soluble model involving four identical particles

A. C. Fonseca and P. E. Shanley

Phys. Rev. C 14, 1343 (1976) - Published 1 October, 1976

Show Abstract

Using a nonrelativistic field theoretic formalism, a soluble model of scattering involving four identical spinless particles is developed and solved numerically. In addition to the elementary "nucleon" (the $n$ ), two composite particles meant to approximate the deuteron and triton are introduced with the couplings $d \leftrightarrow n + n$ and $t \leftrightarrow d + n$ . By consistently excluding all particle-exchange contributions to the three-body sector, four-body integral equations are obtained for the two-to-two processes: $n t \to n t$ , $n t \to d d$ as well as for $d d \to d d$ and $d d \to n t$ . Numerical solutions of the equations are found to satisfy unitarity constraints above the two-, three-, and four-body thresholds. The positions of the four-body bound states are obtained and a complete phase shift calculation is performed. The sum of the total three- and four-body breakup cross sections predicted by the model are displayed as a function of energy and the angular distributions for all 2 → 2 reactions are compared with the four-nucleon data.

NUCLEAR REACTIONS Four-body problem. Spinless model of the four-nucleon system.

New alternative to the resonating group method

R. Raphael, P. C. Tandy, and W. Tobocman

Phys. Rev. C 14, 1355 (1976) - Published 1 October, 1976

Show Abstract

When the cluster model approximation is used with the antisymmetrized coupled equations formalism for the scattering of complex nuclei there results an approximate method which appears to be an attractive alternative to the resonating group method. The antisymmetrized coupled equations formalism leads to a Schrödinger type of equation which has unique solutions in contrast to the resonating group method equation for which redundant solutions exist. The two methods are compared by applying them to the model problem of dineutron-dineutron scattering, and we find that the predicted cross sections are qualitatively similar. In addition, it is shown how the results of a cluster model calculation, which presumably provides a description of direct interaction effects, can be used as input into a Feshbach projection operator type calculation for compound nucleus formation effects.

NUCLEAR REACTIONS Alternative to resonating group method for treating exchange effects in nuclear reactions. Calculation of dineutron-dineutron scattering.

Microscopic study of doorway states in the giant resonance region of ${}^{16}O$

H. L. Yadav and H. V. Geramb

Phys. Rev. C 14, 1369 (1976) - Published 1 October, 1976

Show Abstract

Inelastic proton scattering to the non-normal parity $2^{-}$ (8.88 MeV) state in ${}^{16}O$ has been used as a means to study the applicability of the random-phase-approximation wave functions for the description of doorway states in the giant resonance region. The transition amplitudes are evaluated in a distorted-wave-approximation. The reaction mechanism is described in terms of a direct and a semidirect process, the latter involving the doorway states. The results of this investigation comprise the microscopic radial transition form factors and a differential cross section analysis for proton energies ranging from 24 to 40 MeV.

NUCLEAR REACTIONS ${}^{16}O (p, p^{'})$ , $E = 24 - 40$ MeV; microscopic study of giant resonance region; uses RPA wave functions, DWA.

Levels in ${}^{144}{Nd}$ from the ${}^{143}{Nd} (d, p)$ and the ${}^{146}{Nd} (p, t)$ reactions

S. Raman, R. I. Auble, J. B. Ball, E. Newman, J. C. Wells, Jr., and J. Lin

Phys. Rev. C 14, 1381 (1976) - Published 1 October, 1976

Show Abstract

The energy levels in ${}^{144}{Nd}$ have been studied by means of the ${}^{143}{Nd} (d, p)$ reaction at $E_{d} = 25$ MeV and the ${}^{146}{Nd} (p, t)$ reaction at $E_{p} = 31$ MeV. Angular distributions, values for the transferred angular momenta, and spectroscopic and enhancement factors based on distorted-wave Born approximation calculations have been obtained for $\approx 30$ states. The ( $d, p$ ) spectroscopic strengths have been compared with the results of a calculation based on a two-particle core coupling model.

NUCLEAR REACTIONS ${}^{143}{Nd} (d, p)$ , $E = 25$ MeV; measured $σ (θ)$ . ${}^{146}{Nd} (p, t)$ , $E = 31$ MeV; measured $σ (θ)$ . ${}^{144}{Nd}$ deduced levels, $L$ , $S$ . DWBA analysis.

Resonance neutron capture by ${}^{209}{Bi}$

R. Macklin and J. Halperin

Phys. Rev. C 14, 1389 (1976) - Published 1 October, 1976

Show Abstract

Neutron capture measurements were made for bismuth samples up to the inelastic scattering threshold at 901 keV (lab). All resonance peaks ( $l = 0, 1$ ) between 2.6 and 30 keV were fitted to single level parameters by least squares adjustment. From 30 to 70 keV the resonances reported from recent neutron transmission studies were fitted. Average radiative widths found were (164 ± 45) meV for $l = 0$ and (33.7 ± 3) meV for $l \geq 1$ . The average spacing of $l > 0$ levels was 1.14 ± 0.25 keV for the energy interval 2.6-30 keV. The astrophysical average capture (10.7 mb at $kT = 30$ keV) is little different from earlier estimates but the rate of change with stellar temperature is slower.

NUCLEAR REACTIONS ${}^{209}{Bi} (n, γ)$ , $E = 2.6 - 901$ keV; measured $σ (E)$ ; deduced ${}^{210}{Bi}$ level parameters, average radiative widths, $p$ -wave spacing.

${}^{58}{Ni} (\vec{p}, p^{'})$ reaction at 60 MeV: Study of the analyzing power for inelastic excitation of the giant resonance region of the nuclear continuum and of low-lying bound states

D. C. Kocher, F. E. Bertrand, E. E. Gross, and E. Newman

Phys. Rev. C 14, 1392 (1976) - Published 1 October, 1976

Show Abstract

The analyzing power of the giant resonance region of the nuclear continuum and of low-lying bound states for incident 60-MeV polarized protons has been investigated in the ${}^{58}{Ni} (\vec{p}, p^{'})$ reaction. The measurements are compared with collective-model distorted-wave Born-approximation calculations employing a spin-orbit transition potential of the full-Thomas form and optical-model parameters which give a good description of the analyzing power for proton elastic scattering from ${}^{58}{Ni}$ at 60 MeV. The predicted analyzing powers for the giant quadrupole ( $E 2$ ) resonance at $E_{x} = 16.5$ MeV and for low-lying bound states with $J^{π} = 2^{+}, 3^{-}, and 4^{+}$ are in qualitative agreement with the measurements for $θ_{lab} = 15 - 60 °$ . However, a systematic discrepancy is observed for the quadrupole resonance, where the measurements for $θ_{lab} = 15 - 30 °$ are considerably more negative than the calculations. A similar but less pronounced effect is observed for the strongly excited $2^{+}$ and $3^{-}$ bound states. Improved fits to the analyzing power for the quadrupole resonance are obtained by reducing the spin-orbit diffuseness parameter or by including an attractive imaginary spin-orbit potential. Analysis of the cross section for a weaker resonance at $E_{x} = 13.5$ MeV indicates an $E 2$ assignment. The analyzing power for the unstructured nuclear continuum above the giant resonance region is $A_{y} \approx - 0.05 \pm 0.01$ at most angles between 15 and 40°.

NUCLEAR REACTIONS ${}^{58}{Ni} (\vec{p}, p)$ , $(\vec{p}, p^{'})$ , $E_{p} = 60.2$ MeV, $E_{x} = 0 - 31$ MeV; measured cross section $σ (E_{x}, θ)$ , analyzing power $A_{y} (E_{x}, θ)$ ; discuss excitation of bound states and giant resonances; collective-model distorted-wave analysis. Enriched target.

Transition rates of high-spin states in ${}^{56}{Co}$ and ${}^{56}{Fe}$ : Possible coexistence of prolate- and oblate-like configurations in ${}^{56}{Fe}$

D. G. Sarantites, J. Urbon, and L. L. Rutledge, Jr.

Phys. Rev. C 14, 1412 (1976) - Published 1 October, 1976

Show Abstract

The decay properties of the high-spin states in ${}^{56}{Co}$ and ${}^{56}{Fe}$ have been investigated via the ${}^{54}{Fe} (α, p n) {}^{56}{Co}^{*} (γ)$ and ${}^{54}{Fe} (α, 2 p) {}^{56}{Fe}^{*} (γ)$ reactions in the energy range 20.4-29.5 MeV. From measurements of excitation functions and angular distributions of individual $γ$ rays with a Ge(Li)-NaI(T1) anti-Compton spectrometer, and from $γ γ$ -coincidence experiments new levels in ${}^{56}{Co}$ have been identified at 2282.6 ( $7_{1}^{+}$ ), 2371.9 ( $6_{1}^{+}$ ), 3638.0 ( $8_{1}^{+}$ ), 4180.2 ( $9_{1}^{+}$ ), and 5274.6 ( $10_{1}^{+}$ ) keV with the deduced $J^{π}$ values in parentheses. Similarly levels in ${}^{56}{Fe}$ have been confirmed at 3388.4 ( $6_{1}^{+}$ ), 3755.8 ( $6_{2}^{+}$ ), 4700.6 ( $7_{1}^{+}$ ), 5255.3 ( $8_{1}^{+}$ ), and 5626.8 ( $8_{2}^{+}$ ) keV and the $J^{π}$ values in parentheses have been deduced. The angular distributions in conjunction with the associated attenuation factors were analyzed to yield multipole mixing ratios $δ (\frac{E 2}{M 1})$ .The mean lifetimes $τ$ of these states were also carefully measured by extrapolation to the detection threshold of the effective mean lifetimes extracted from Doppler-broadened line shapes obtained at four bombardment energies between 20.4 and 29.5 MeV. The values obtained in ${}^{56}{Co}$ are 2282.6 KeV (>2000 fs), 2371.9 keV (60 ± 30 fs), 3638.0 keV ( $80_{- 30}^{+ 40}$ fs), 4180.2 keV (590 ± 60 fs), and 5274.6 keV ( $60_{- 20}^{+ 40}$ fs); and those in ${}^{56}{Fe}$ are 3388.4 keV (>2000 fs), 3755.8 keV ( $180_{- 30}^{+ 40}$ fs), 4700.6 keV (120 ± 40 fs), 5255.3 keV (500 ± 50 fs), and 5626.8 keV ( $100_{- 20}^{+ 40}$ fs). For most of the transitions from the high-spin states in ${}^{56}{Co}$ and ${}^{56}{Fe} B (Λ)$ values were obtained. The results for ${}^{56}{Fe}$ are compared with recent calculations based on the aligned coupling scheme indicating possible coexistence of quasiband structures with prolate- and oblate-like configurations. The results for ${}^{56}{Co}$ are compared with other recent shell-model calculations and good agreement is observed.

NUCLEAR REACTIONS ${}^{54}{Fe} (α, p n) {}^{56}{Co}^{*} (γ)$ and ${}^{54}{Fe} (α, 2 p) {}^{56}{Fe}^{*} (γ)$ , $E = 21 - 30$ MeV, enriched targets. Measured, $E_{γ}$ , $I_{γ}$ , $I_{γ} (θ)$ , $σ (E)$ , ${Δ \bar{E}}_{γ} (E, τ)$ , $γ γ$ coin., deduced levels in ${}^{56}{Co}$ and ${}^{56}{Fe}$ , $J$ , $π$ , branching ratios, $τ_{level}$ , $δ (\frac{E 2}{M 1})$ , $B (E 2)$ and $B (M 1)$ values; Ge(Li) detectors, Ge(Li)-NaI(T1) anti-Compton spectrometer, 2.2. keV at 1332.5 keV.

Alignment and decay of isobaric analog states formed by ( $p, n$ ) reactions

G. R. Rao and N. Austern

Phys. Rev. C 14, 1429 (1976) - Published 1 October, 1976

Show Abstract

Calculations are presented here for the angular correlation between the neutron and proton in ( $p, n p$ ) reactions, where the ( $p, n$ ) reaction excites the isobaric analog state of the target ground state, which then decays by proton emission. The ( $p, n$ ) reaction is treated as a charge-exchange direct reaction and calculations are done in the plane wave Born approximation, with a microscopic proton-nucleus interaction taken as a sum of two-body interactions. While the commonly used macroscopic charge-exchange interaction $V_{0} (r) \vec{t} \cdot \vec{T}$ is spherically symmetric, a microscopic interaction with individual nucleons allows higher multipole transfers and can lead to alignment of the isobaric analog state. The alignment of the isobaric analog state is sensitive to the relative importance of the higher multipole transfers that contribute to the formation of the IAS. The importance of these higher multipoles depends on the properties of the nucleon-nucleon interaction and also on the angle of neutron emission, which affects the momentum transfer. The alignment of the isobaric analog state can be inferred from the study of the decay channels of the isobaric analog state. For $A ≳ 60$ , the isobaric analog state can decay by particle emission. Thus, the alignment of the isobaric analog state can be studied by the measurement of angular distributions of the decay protons in coincidence with the neutrons. Illustrative calculations of the alignment of the isobaric analog state and the angular distribution of decay protons are presented here for several nuclei, and comparisons with experimental measurements of $n - p$ coincidence angular distributions for ${}^{91}{Zr}$ and ${}^{95}{Mo}$ are presented. The anisotropies in these two cases are weak. However, strong alignments of the isobaric analog state found theoretically for $A ≲ 60$ suggest that ( $p, n γ$ ) correlation experiments for those nuclei would be interesting.

NUCLEAR REACTIONS ${}^{87}{Sr}$ , ${}^{91}{Zr}$ , ${}^{93}{Nb}$ , ${}^{95}{Mo}$ , ${}^{99}{Tc} (p, n \bar{p})$ , $E = 17$ MeV, calculated $n - \bar{p}$ angular correlation; ${}^{43}{Ca}$ , ${}^{45}{Sc}$ , ${}^{47}{Ca}$ , ${}^{51}V$ , ${}^{87}{Rb}$ , ${}^{99}{Ru}$ ( ${}^{99}{Ru} (p, n γ)$ ) IAS, $E = 17$ MeV, calculated alignment of magnetic substates; ${}^{91}{Zr}$ , ${}^{95}{Mo}$ ( ${}^{95}{Mo} (p, n \bar{p})$ ), $E = 17$ MeV, measured $n - \bar{p}$ angular correlation.

Neutron transmission and capture gamma-ray measurements of ${}^{120}{Sn} + n$

R. F. Carlton, S. Raman, J. A. Harvey, and G. G. Slaughter

Phys. Rev. C 14, 1439 (1976) - Published 1 October, 1976

Show Abstract

Neutron transmission and neutron capture $γ$ -ray measurements have been performed upon 98.4% enriched samples of ${}^{120}{Sn}$ . The transmission measurements were made at 18- and 80-m neutron flight paths. Neutrons were detected by a ${}^{6}{Li}$ glass scintillator. Parameters have been obtained for 251 resonances up to 98 keV. From the shapes of the resonances, $l$ -value assignments have been made for 70% of the resonances. Level spacings and strength functions for $s$ - and $p$ -wave neutrons have been obtained. Neutron capture $γ$ rays from 16 resonances, obtained with a Ge(Li) detector, have been utilized to determine the levels in ${}^{121}{Sn}$ . New spin and parity assignments have been made for many of the levels. Four new levels have been found. The neutron separation energy was determined to be 6170.3 ± 2.0 keV. The ${}^{121}{Sn}$ level scheme has been compared with those for ${}^{117}{Sn}$ and ${}^{119}{Sn}$ to investigate systematic behavior.

NUCLEAR REACTIONS ${}^{120}{Sn} (n)$ , $E = 0.1 - 100$ keV; measured total $σ (E)$ . ${}^{121}{Sn}$ deduced resonances, $l$ , resonance parameters, level spacing, $s -$ , $p$ -wave neutron strength functions. ${}^{120}{Sn} (n, γ)$ , $E = 0.1 - 7$ keV; measured $E_{γ}$ , $I_{γ}$ . ${}^{121}{Sn}$ deduced levels, $J$ , $π$ , neutron separation energy. ${}^{117, 119, 121}{Sn}$ systematics. Enriched targets.

Observation of excited states in ${}^{206}{Hg}$

W. R. Hering, H. Puchta, W. Trautmann, R. L. McGrath, and H. Bohn

Phys. Rev. C 14, 1451 (1976) - Published 1 October, 1976

Show Abstract

We investigated ${}^{206}{Hg}$ , the missing link for particle-vibration coupling studies around ${}^{208}{Pb}$ . In ${}^{18, 17}O$ induced reactions on ${}^{204}{Hg}$ we identified $γ$ rays from states at 1.068 and 2.102 MeV in ${}^{206}{Hg}$ . Relying on theoretical arguments we propose spins $2^{+}$ and $4^{+}$ , respectively.

NUCLEAR REACTIONS ${}^{204}{Hg}$ ( ${}^{18}O$ , ${}^{16}O$ ), ( ${}^{17}O$ , ${}^{16}O$ ), $E ({}^{18}O) = 75 and 81$ MeV, $E ({}^{17}O) = 81$ MeV. Measured particle- $γ$ and $γ - γ$ coin., deduced ${}^{206}{Hg}$ level energies (and spins). Enriched targets.

Search for ultradense nuclei in relativistic collisions of Ar on Ca, U, and Pb

K. Frankel and J. Stevenson

Phys. Rev. C 14, 1455 (1976) - Published 1 October, 1976

Show Abstract

We have placed upper limits of ∼ 100 nb on the production cross section of long-lived ( $τ_{\frac{1}{2}} ≳ 10^{- 9} sec$ ) nuclei with $Z ≳ 26$ and energy $E ≳ 10$ MeV/nucleon in interactions of 100- to 450-MeV/nucleon ${}^{40}{Ar}$ ions with U and Ca targets.

NUCLEAR REACTIONS ${}^{40}{Ar} ({}^{40}{Ca}, H [Z > 26])$ , $E = 13.2 - 15.8$ GeV; ${}^{40}{Ar} ({}^{208}{Pb}, H [Z > 26])$ , $E = 4.0 - 8.0$ GeV; ${}^{40}{Ar} ({}^{238}U, H [Z > 26])$ , $E = 4.0 - 17.0$ GeV; No nuclei $Z > 26$ , $E ≳ 10$ MeV/nucleon, $τ_{\frac{1}{2}} ≳ 10^{- 9}$ found.

Systematics of optimum $Q$ values in multinucleon transfer reactions induced by heavy ions

T. Mikumo, I. Kohno, K. Katori, T. Motobayashi, S. Nakajima, M. Yoshie, and H. Kamitsubo

Phys. Rev. C 14, 1458 (1976) - Published 1 October, 1976

Show Abstract

The most probable effective $Q$ values, $Q_{eff}^{m}$ , for multinucleon transfer reactions $A (a, b) B (M_{b} < M_{a})$ have been systematically studied on $fp$ -shell nuclei and Zr-Mo isotopes induced by ${}^{14}N$ and ${}^{12}C$ , in the energy range between 60 and 100 MeV. As regards the "quasielastic" part of the bump in the energy spectrum, the dependence of $Q_{eff}^{m}$ on the incident and outgoing channel variables, i.e., $A$ , $a$ , $E_{i}$ , $θ$ , and $n$ , the number of transferred nucleons, has been extensively investigated. The present data, together with those obtained at higher energies by the Dubna group, show systematic behaviors of $Q_{eff}^{m}$ (i) for a given $A (a, b) B$ and $E_{i}$ , $Q_{eff}^{m}$ changes little with $θ_{lab}$ , (ii) at a given $E_{i}$ , $Q_{eff}^{m}$ of ( $a, b$ ) is nearly the same for adjacent $A$ and is not sensitive to their individual nuclear structure, and (iii) the linear relation $Q_{eff} = α_{eff} n + β_{eff}$ holds for $n \leq 4 - 5$ , whereas the linearity breaks down for larger $n$ . The relation $α_{eff} = - 0.1 (E_{i} - V_{c}^{i}) - 0.9$ MeV holds for a wide range of reactions. The ratio of the most probable effective velocity to the incident velocity $\frac{ν_{f}^{m}}{ν_{i}}$ at the transfer region decreases from about unity to 0.4 - 0.5 as $n$ increases. The differences in reaction mechanisms for smaller $n$ and larger $n$ have been discussed.

NUCLEAR REACTIONS ${}^{52, 53}{Cr} ({}^{14}N, x)$ , $x = {}^{13, 12}C, {}^{12, 11, 10}B, {}^{10, 9, 7}{Be}, {}^{7, 6}{Li}, {}^{4}{He}$ ; $E = 64, 70, 80, 90, 95$ MeV, $θ = 10 - 33 °$ ; ${}^{90}{Zr}$ ( ${}^{14}N$ ; ${}^{13, 12}C$ , ${}^{11}B$ ), $E = 75$ MeV, $θ = 30.5 °$ ; ${}^{A}{Mo} ({}^{14}N, x)$ , $A = 92, 94, 95, 96, 97, 98, 100$ , $E = 97$ MeV, $x = {}^{13, 12}C, {}^{12, 11, 10}B, {}^{10, 9, 7}{Be}, {}^{7, 6}{Li}, {}^{4}{He}$ , $θ = 25, 30 °$ ; ${}^{92}{Mo} ({}^{12}C; x)$ , $x = {}^{10}B, {}^{10, 9, 7}{Be}, {}^{7, 6}{Li}$ , $E = 90$ MeV, $θ = 20 °$ ; measured energy spectra of $x$ and optimum $Q$ values.

Select page:

Physical Review C

Recent Articles

Filter

Recent Issues

$g$ factor of the 635.4 keV level in ${}^{171}{Tm}$

Bounds on the rate of ${}^{1}H (p, e^{+} ν) {}^{2}H$ in impulse approximation

Upper limit for the ${}^{1}H (n, γ γ) {}^{2}H$ cross section

Doubly radiative $np$ capture

Experimental study of giant dipole and quadrupole resonances in ${}^{16}O$

$γ$ -ray decay of the first $T = 2$ state in ${}^{36}{Ar}$

Isobaric analog impurities from neutron capture and transmission by magnesium

Two-nucleon exchange cuts in the Amado model for $n - d$ scattering

Soluble model involving four identical particles

New alternative to the resonating group method

Microscopic study of doorway states in the giant resonance region of ${}^{16}O$

Levels in ${}^{144}{Nd}$ from the ${}^{143}{Nd} (d, p)$ and the ${}^{146}{Nd} (p, t)$ reactions

Resonance neutron capture by ${}^{209}{Bi}$

${}^{58}{Ni} (\vec{p}, p^{'})$ reaction at 60 MeV: Study of the analyzing power for inelastic excitation of the giant resonance region of the nuclear continuum and of low-lying bound states

Transition rates of high-spin states in ${}^{56}{Co}$ and ${}^{56}{Fe}$ : Possible coexistence of prolate- and oblate-like configurations in ${}^{56}{Fe}$

Alignment and decay of isobaric analog states formed by ( $p, n$ ) reactions

Neutron transmission and capture gamma-ray measurements of ${}^{120}{Sn} + n$

Observation of excited states in ${}^{206}{Hg}$

Search for ultradense nuclei in relativistic collisions of Ar on Ca, U, and Pb

Systematics of optimum $Q$ values in multinucleon transfer reactions induced by heavy ions

Filter

Recent Issues

Filter

Article Lookup

Enter a citation