Study of levels in 24Mg

1968 ◽  
Vol 46 (12) ◽  
pp. 1381-1401 ◽  
Author(s):  
R. W. Ollerhead ◽  
J. A. Kuehner ◽  
R. J. A. Levesque ◽  
E. W. Blackmore
Keyword(s):  
Angular Correlation ◽  
Beta Decay ◽  
Rotational Band ◽  
Ground State ◽  
Present Experiment ◽  
Gamma Ray ◽  
Axially Symmetric ◽  
Excitation Energies ◽  
Rotational Model ◽  
Rotational Bands

Nineteen levels in 24Mg have been studied utilizing the reaction 12C(16O, αγ)24Mg. Angular correlation measurements have established the spins and parities of levels at excitation energies of 7.35, 7.56, 7.62, 8.44, 8.65, 9.00, 9.15, and 10.1 MeV as 2+, 1−, 3−, 1−, 2+, 2+, 1−, and 0+ respectively. Levels at 8.12 and 13.18 MeV have been identified as the 6+ and 8+ members of the K = 0 ground-state rotational band; levels at 7.81 and 9.52 MeV have been identified as the 5+ and 6+ members of the K = 2 rotational band based on the 2+ level at 4.23 MeV. The existence of doublets has been established at excitation energies of 8.44 and 9.52 MeV; in each case, one member of the doublet is populated in the beta decay of 24Al, and the present experiment indicates that these two levels have spin and parity 4+. Assignments are also suggested for levels at 7.75 MeV (1+) and 8.36 MeV (2+). Gamma-ray spectra have been obtained for levels at 8.86, 9.28, and 9.46 MeV. The properties of levels assigned to rotational bands are compared to the predictions of the rotational model for an axially symmetric nucleus.

Branching Ratios and Lifetimes of 25Mg Levels below 5.2 MeV

1974 ◽  
Vol 52 (23) ◽  
pp. 2329-2342 ◽  
Author(s):  
R. W. Ollerhead ◽  
D. C. Kean ◽  
R. M. Gorman ◽  
M. B. Thomson
Keyword(s):  
Doppler Shift ◽  
Gamma Ray ◽  
Branching Ratios ◽  
Surface Barrier ◽  
Surface Barrier Detector ◽  
Rotational Model ◽  
Rotational Bands ◽  
Barrier Detector ◽  
Combined Data

All levels below 5.2 MeV in 25Mg have been studied using the reaction 25Mg(p, p′γ). In-elastically scattered protons were detected in an annular surface barrier detector located at 180°; coincidence gamma-ray spectra were obtained at Ge (Li) detector angles of 90°, 45°, and 135°. Level energies were determined from unshifted gamma-ray energies recorded in the 90° spectra. Lifetimes were obtained from the attenuated Doppler shift of gamma-ray energies recorded in spectra taken at forward and backward angles. Branching ratios were deduced from the combined data of all three angles. The identification of levels as members of rotational bands is discussed, and transition strengths deduced from the present measurements are compared with predictions of the simple rotational model.

Branching Ratios and Lifetimes of 25Mg Levels between 5.2 and 6.1 MeV

1975 ◽  
Vol 53 (2) ◽  
pp. 123-132 ◽  
Author(s):  
R. W. Ollerhead ◽  
D. C. Kean ◽  
S. G. T. Leong ◽  
C. Doekes ◽  
T. M. R. Meadley
Keyword(s):  
Gamma Ray ◽  
Branching Ratios ◽  
Surface Barrier ◽  
Surface Barrier Detector ◽  
Ground State Band ◽  
Rotational Model ◽  
Rotational Bands ◽  
Barrier Detector ◽  
State Band ◽  
Combined Data

All levels between 5.2 and 6.1 MeV in 25Mg have been studied using the reaction 25Mg(p,p′γ). Inelastically scattered protons were detected in an annular surface barrier detector located at 180°; coincidence gamma-ray spectra were obtained at Ge(Li) detector angles of 90, 45, and 135°. Level energies were determined from unshifted gamma-ray energies recorded in the 90° spectra. Lifetimes were obtained from the attenuated Doppler shift of gamma-ray energies recorded in spectra taken at forward and backward angles. Branching ratios were deduced from the combined data of all three angles. The identification of levels as members of rotational bands is discussed, and transition strengths deduced from the present measurements are compared with predictions of the simple rotational model. In particular, evidence is presented for the identification of a level at 5535 keV as the 11/2 member of the ground state band, levels at 5522 and 5794 keV as the 5/2 and 11/2 members of the Kπ = 1/2− band, and a level at 6040 keV as the 11/2 member of a Kπ = 9/2+ band.

GAMMA-RAY ANGULAR CORRELATIONS FROM ALIGNED NUCLEI PRODUCED BY NUCLEAR REACTIONS

1961 ◽  
Vol 39 (6) ◽  
pp. 788-824 ◽  
Author(s):  
A. E. Litherland ◽  
A. J. Ferguson
Keyword(s):  
Angular Correlation ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Nuclear Reactions ◽  
Residual Nucleus ◽  
Incident Beam ◽  
Nuclear Spectroscopy ◽  
Population Parameters ◽  
Axially Symmetric ◽  
Angular Correlations

Two general procedures for the measurement and analysis of angular correlations of gamma radiations from nuclear reactions are described which have wide applications in nuclear spectroscopy for the determination of spins and gamma-ray multipolarities. Cases can be studied by these methods when the reaction proceeds through a compound state too complex to allow the usual analysis to be made, for example where several levels overlap or where direct interaction is dominant. The basis of these procedures is to exploit the simplifications brought about by making the reacting system axially symmetric. A sharp gamma-ray-emitting state formed in such a system can be regarded as aligned and described in terms of a relatively small number of population parameters for the magnetic substates. In the first procedure, a state Y* is prepared by a nuclear reaction X(h1h2) Y* in which h2 is unobserved. The state Y* has axial symmetry about the beam axis. From coincidence angular correlation measurements of two cascade gamma rays from Y*, the unknown population parameters for Y* together with the nuclear spins and gamma-ray multipolarities can be determined. In the second procedure, h2 is measured in a small counter at 0° or 180° relative to the incident beam. It is then shown that the quantum numbers of the magnetic substates of Y* which can be populated do not exceed the sum of the spins of X, h1, and h2. In cases where the sum of the spins does not exceed [Formula: see text], the angular correlation of the gamma rays from the aligned state depends only upon the properties of the states in the residual nucleus. Theoretical expressions for angular correlations from aligned states are given, together with a method whereby existing extensive tables of coefficients can be used to calculate them. The results of two recent experiments are discussed as examples.

Ground State Rotational Bands in 16O, 40Ca and 208Pb?

1975 ◽  
Vol 30 (2) ◽  
pp. 158-160 ◽  
Author(s):  
K. Lezuo
Keyword(s):  
Rotational Band ◽  
Ground State ◽  
Rotational Bands

Abstract It is pointed out that a considerable amount of evidence exists to support the concept of a ground state rotational band based on tetrahedral deformation for 16O, 40Ca and 208Pb. The possible meaning of this interpretation as well as other well-known alternatives are discussed.

WEAK GAMMA-RAY TRANSITIONS IN 20Ne

1967 ◽  
Vol 45 (12) ◽  
pp. 3836-3847
Author(s):  
C. Broude ◽  
A. E. Litherland ◽  
R. W. Ollerhead ◽  
T. K. Alexander
Keyword(s):  
Angular Correlation ◽  
Ground State ◽  
Gamma Ray ◽  
Decay Modes ◽  
Total Level ◽  
Level Width ◽  
Weak Transitions

Various techniques have been applied to the measurement of weak gamma-ray decay modes of the 4.97-MeV 2− and 7.02-MeV 4− states in 20Ne excited by the reaction 12C(12C, αγ)20Ne. The M2 decay of the 4.97-MeV state to the ground state is 0.6 ± 0.2% of the total level width, corresponding to an M2 width of 2 × 10−3 Weisskopf units. The M2–E3 transition from the 7.02-MeV state to the 1.63-MeV 2+ state is 0.5% ± 0.2% of the level width; if all M2, this would correspond to an inhibition of 1.4 × 10−2 Weisskopf units, if all E3, to an enhancement of 6 Weisskopf units. The reliability of the measurements has been checked by angular correlation measurements of the weak transitions.

14.—Ground State Rotational Bands in 158Dy, 160Dy and 162Dy

1972 ◽  
Vol 70 ◽  
pp. 155-163 ◽  
Author(s):  
G. T. Ewan ◽  
G. I. Andersson
Keyword(s):  
Gamma Rays ◽  
Ground State ◽  
Gamma Ray ◽  
Angular Distributions ◽  
Rotational Bands ◽  
Weak Evidence ◽  
Gamma Coincidence ◽  
Inertia Model ◽  
Coincidence Spectra ◽  
Variable Moment

SynopsisLevels in the ground state bands of 158Dy, 160Dy and 162Dy have been populated by (α, 2n) reactions on metallic targets of separated 156Gd, 158Gd and 160Gd isotopes. Two Ge(Li) detectors were used to study singles gamma-ray spectra, gamma-ray angular distributions, gamma-gamma coincidence spectra and relative yields of gamma-rays for bombarding energies from 20 to 27 MeV. Transitions from all levels in the ground state bands up to the 12+ member were identified and the following level energies in keV established: 158Dy: 0 (0+), 99·0 (2+), 317·4 (4+), 637·9 (6+), 1044·1 (8+), 1520·1 (10+) and 2049·4 (12+); 160Dy: 0 (0+), 86·7 (2+), 283·7 (4+), 581·4 (6+), 967·4 (8+), 1429·0 (10+), 1951·7 (12+); 162Dy: 0 (0+), 80·7 (2+), 265·7 (4+), 548·5 (6+), 921·1 (8+), 1374·8 (10+) and 1901·0 (12+). There is weak evidence for the 14+ levels in 158Dy and 160Dy. The level energies are compared with calculated values using the variable moment of inertia model.

K X-Ray and Gamma-Ray Angular Correlations in the Decay of 113Sn and 133Ba, using a High Efficiency Sum-Peak Coincidence Scintillation Spectrometer

1971 ◽  
Vol 49 (13) ◽  
pp. 1769-1772 ◽  
Author(s):  
K. Venkata Ramana Rao ◽  
V. Lakshminarayana
Keyword(s):  
Angular Correlation ◽  
Beta Decay ◽  
High Efficiency ◽  
Gamma Ray ◽  
X Ray ◽  
Angular Correlations ◽  
Nuclear Environment

K-capture isotopes 113Sn and 133Ba are used with a sum-peak coincidence scintillation spectrometer arrangement to study the K X-ray – gamma-ray angular correlation. The effects of the type of beta decay, the nuclear environment, and three-gamma cascades with intermediate gamma ray unobserved are investigated. No anisotropy could be detected, supporting the theory of Dolginov.

scholarly journals Collective rotation from ab initio theory

2015 ◽  
Vol 24 (09) ◽  
pp. 1541002 ◽  
Author(s):  
M. A. Caprio ◽  
P. Maris ◽  
J. P. Vary ◽  
R. Smith
Keyword(s):  
Ab Initio ◽  
Rotational Band ◽  
Configuration Interaction ◽  
Collective Phenomena ◽  
Excitation Energies ◽  
Nuclear Theory ◽  
Electromagnetic Moments ◽  
Rotational Bands ◽  
Ab Initio Theory ◽  
Collective Rotation

Through ab initio approaches in nuclear theory, we may now seek to quantitatively understand the wealth of nuclear collective phenomena starting from the underlying internucleon interactions. No-core configuration interaction (NCCI) calculations for p-shell nuclei give rise to rotational bands, as evidenced by rotational patterns for excitation energies, electromagnetic moments and electromagnetic transitions. In this review, NCCI calculations of 7–9 Be are used to illustrate and explore ab initio rotational structure, and the resulting predictions for rotational band properties are compared with experiment. We highlight the robustness of ab initio rotational predictions across different choices for the internucleon interaction.

Positive-Parity Bands in 29Si

1971 ◽  
Vol 49 (10) ◽  
pp. 1263-1274 ◽  
Author(s):  
A. A. Pilt ◽  
R. H. Spear ◽  
R. V. Elliott ◽  
J. A. Kuehner
Keyword(s):  
Angular Distribution ◽  
Excited State ◽  
Linear Polarization ◽  
Ground State ◽  
Gamma Ray ◽  
Positive Parity ◽  
Rotational Bands ◽  
Mixing Ratios ◽  
First Excited State ◽  
Nilsson Model

A study has been made of several high spin members of the ground state (Kπ = 1/2+) and first-excited state (Kπ = 3/2+) rotational bands in the presumed oblate nucleus 29Si. Gamma-ray angular distribution and linear polarization measurements have confirmed the spin and parity of the 4081 keV level to be 7/2+, and levels at 4742 and 5283 keV have been shown to have Jπ = 9/2+ and (7/2+, 3/2+) respectively. Branching and mixing ratios for the transitions from these states have also been determined; in conjunction with previously measured lifetimes, transition strengths are calculated. The results are compared with the predictions of a Nilsson-model calculation including the effects of coriolis mixing of the low-lying positive parity bands.

SPINS OF EXCITED STATES OF Os188

1959 ◽  
Vol 37 (6) ◽  
pp. 755-774 ◽  
Author(s):  
W. J. King ◽  
M. W. Johns
Keyword(s):  
Angular Correlation ◽  
Excited States ◽  
Beta Decay ◽  
Decay Scheme ◽  
Gamma Ray ◽  
Correlation Data ◽  
Conversion Coefficients

Seven excited states of Os188 populated through the beta decay of Re188 have been studied by gamma–gamma angular correlation experiments. The data for the various cascades fit the following theoretical functions: (all gamma-ray energies are in kev and the description following each cascade refers to the first transition) 478–155 (2–2–0, 99.7% E2, δ +ve), 931–155 (0–2–0), 672–633 (2–2–0), 97% M1, δ −ve or 3–2–0, 94% M1, δ −ve or conceivably 4–2–0), 828–633 (2–2–0, 98% M1, δ −ve or conceivably 3–2–0, 80% M1, δ −ve), 1132–633 (0–2–0), and 1308–633 (2–2–0, 98% M1, δ −ve). Some attenuation occurred in the correlations involving the 155-kev gamma ray. The K-conversion coefficients for the 478- and 633-kev transitions have been measured as 0.023 ± 0.003 and 0.010 ± 0.002 respectively, confirming the E2 character for these transitions obtained by angular correlation. These results, coupled with data concerning log ft values and gamma-ray intensities, lead to the following spin and parity assignments for levels in Os188: 155 (2+), 633 (2+), 1086 (0+), 1306 (2+ or 3+), 1461 (2+), 1765 (0+), 1941 (2+), and 1958 (1+ or 2+).The 631–137 correlation data in Os186 was found to fit an attenuated 2–2–0 function with the first transition 99% E2 and δ −ve. This result supports the established decay scheme for this nucleus.

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