Mesures de Rapports d'Embranchement et de Vies Moyennes dans 30Si

1972 ◽  
Vol 50 (3) ◽  
pp. 278-286 ◽  
Author(s):  
A. Gallmann ◽  
F. Haas ◽  
M. Toulemonde
Keyword(s):  
Shell Model ◽  
Gamma Rays ◽  
Doppler Shift ◽  
Branching Ratios ◽  
Matrix Elements ◽  
Excitation Energies ◽  
Doppler Shift Attenuation ◽  
Annular Detector ◽  
Γ Rays

Gamma rays from the decay of 30Si levels with excitation energies less than 6.0 MeV have been studied by the 27Al(α, pγ)30Si reaction. The γ rays were detected in a Ge(Li) detector in coincidence with protons observed in an annular detector placed at 180°. Branching ratios and lifetimes have been extracted. The lifetimes have been measured by the Doppler-shift attenuation method.The electromagnetic matrix elements for some of the observed levels were compared with recent many-particle shell model and core-coupling calculations.

Lifetimes and decay modes of energy levels in 25Mg

1968 ◽  
Vol 46 (18) ◽  
pp. 2039-2053 ◽  
Author(s):  
J. F. Sharpey-Schafer ◽  
R. W. Ollerhead ◽  
A. J. Ferguson ◽  
A. E. Litherland
Keyword(s):  
Gamma Rays ◽  
Doppler Shift ◽  
Energy Levels ◽  
Branching Ratios ◽  
Collective Model ◽  
Incident Proton ◽  
Crystal Spectrometer ◽  
Decay Modes ◽  
Mirror Nucleus ◽  
Doppler Shift Attenuation

Lifetimes of energy levels in 25Mg have been measured using the Doppler-shift attenuation method. The levels were exicted by the 25Mg(p, p′γ) reaction with incident proton energies between 3.8 and 7.0 MeV. The gamma rays were detected in a three-crystal spectrometer consisting of a 40 cm3 Ge(Li) detector surrounded by a large NaI(Tl) crystal in the form of a split annulus. Mean lifetimes found, given in fs, are: τ(1611-keV level) = [Formula: see text], τ(1962) = [Formula: see text], τ(2565) = 59 ± 26, τ(2736) = 288 ± 20, τ(2803) = 27 ± 6, τ(3399) = 33 ± 19, τ(3408) < 20, τ(3903) < 20, τ(3969) = 24 ± 11, τ(4055) = 53 ± 10, and τ(5005) < 26. The decay modes and branching ratios of levels up to 4055-keV excitation are given. The results are compared with the mirror nucleus 25Al and discussed in terms of the collective model.

Properties of the 9.699 MeV level in 28Si

1969 ◽  
Vol 47 (16) ◽  
pp. 1725-1729 ◽  
Author(s):  
N. Anyas-Weiss ◽  
A. M. Charlesworth ◽  
L. E. Carlson ◽  
K. P. Jackson ◽  
R. E. Azuma
Keyword(s):  
Lower Limit ◽  
Gamma Rays ◽  
Large Volume ◽  
Doppler Shift ◽  
Branching Ratios ◽  
Doppler Shift Attenuation ◽  
Doppler Shift Attenuation Method

The decay of the 9.699 MeV level in 28Si has been studied using the reaction 27Al(p,γ)28Si at Ep = 1724 keV. Gamma rays from the decay of the 9.699 MeV level were observed with large-volume Ge(Li) detectors. Branching ratios for the decay of the 9.699 MeV level have been obtained and a lower limit for the lifetime of this level has been measured to be [Formula: see text] using the Doppler-shift attenuation method.

Lifetime measurements of the six lowest lying levels in 35Cl

1969 ◽  
Vol 47 (12) ◽  
pp. 1295-1306 ◽  
Author(s):  
F. Ingebretsen ◽  
T. K. Alexander ◽  
O. Häusser ◽  
D. Pelte
Keyword(s):  
Gamma Rays ◽  
Doppler Shift ◽  
Gamma Ray ◽  
Level Structure ◽  
Branching Ratios ◽  
Distance Method ◽  
Lifetime Measurements ◽  
Mixing Ratios ◽  
Doppler Shift Attenuation ◽  
Recoil Distance

The energies, gamma-ray branching ratios, and mean nuclear lifetimes of the six lowest lying levels in 35Cl have been measured. Gamma rays following the reaction 32S(α,pγ)35Cl were studied using two Ge(Li) detectors with 15-cm3 and 40-cm3 active volumes respectively. The lifetimes of the five lowest lying levels were measured using the Doppler shift attenuation method, with the results: 1219 keV, [Formula: see text]; 1763 keV, 0.55 ± 0.15 ps; 2646 keV, 0.30 ± 0.09 ps; 2695 keV, <0.03 ps; and 3003 keV, <0.05 ps. The lifetime of the 3163-keV level was measured to be 60 ± 7 ps, using a recoil distance method. The level structure is discussed taking into account known lifetimes, spins, parities, and gamma-ray mixing ratios.

scholarly journals A Search for an Excited Kp=0+ Rotational Band in 24Mg

1976 ◽  
Vol 29 (3) ◽  
pp. 139 ◽  
Author(s):  
D Branford ◽  
LE Carlson ◽  
FCP Huang ◽  
N Gardner ◽  
TR Ophel ◽  
...  
Keyword(s):  
Shell Model ◽  
Quadrupole Moment ◽  
Rotational Band ◽  
Doppler Shift ◽  
Transition Rates ◽  
Model Calculations ◽  
Doppler Shift Attenuation ◽  
Doppler Shift Attenuation Method ◽  
Absolute Transition ◽  
Good Agreement

A search is described for an excited Kn = 0+ rotational band based on the 6� 44 MeV level of 24Mg. Mean nuclear lifetimes have been measured by the Doppler shift attenuation method using the 12C('60,a)24Mg reaction and the results are 't'm = 66�29, 28�7 and 13�3 fs for levels at 6'44, 8�65 and 10� 58 MeV respectively. The absolute transition rates found for the y decays from the 6�44 and 8�65 MeV levels are in good agreement with the results of shell model calculations if it is assumed that these levels are the 0+ and 2 + members respectively of the excited Kn = 0+ rotational band. Based on this assumption, a result Qoo = 0�48 �0�08b is obtained for the intraband quadrupole moment. From a study of the 23Na(p, y) reaction, it is established that the J = 4 levels at 12� 63 and 13�05 MeV do not decay by enhanced E2 transitions to the 8� 65 MeV level. This suggests that neither of these levels is the 4 + member of the excited Kn = 0+ rotational band. An assignment of J" = 4+ is made to one member of the doublet at 10�58 MeV.

LIFETIME MEASUREMENTS OF STATES IN O18 AND Ne22

1964 ◽  
Vol 42 (6) ◽  
pp. 1311-1323 ◽  
Author(s):  
M. A. Eswaran ◽  
C. Broude
Keyword(s):  
Excited State ◽  
Ground State ◽  
Doppler Shift ◽  
State Transition ◽  
Branching Ratios ◽  
Ground State Transition ◽  
Lifetime Measurements ◽  
Doppler Shift Attenuation ◽  
First Excited State ◽  
Doppler Shift Attenuation Method

Lifetime measurements have been made by the Doppler-shift attenuation method for the 1.98-, 3.63-, 3.92-, and 4.45-Mev states in O18 and the 1.28-, 3.34-, and 4.47-Mev states in Ne22, excited by the reactions Li7(C12, pγ)O18 and Li7(O16, pγ)Ne22. Branching ratios have also been measured. The results are tabulated.[Formula: see text]The decay of the 3.92-Mev state in O18 is 93.5% to the 1.98-Mev state and 6.5% to the ground state and of the 4.45-Mev state 74% to the 3.63-Mev state, 26% to the 1.98-Mev state, and less than 2% to the ground state. In Ne22, the ground-state transition from the 4.47-Mev state is less than 2% of the decay to the first excited state.

Lifetimes of Low Lying Levels of 18O, 18Ne

1974 ◽  
Vol 52 (15) ◽  
pp. 1381-1388 ◽  
Author(s):  
A. B. McDonald ◽  
T. K. Alexander ◽  
O. Häusser ◽  
G. J. Costa ◽  
J. S. Forster ◽  
...  
Keyword(s):  
Doppler Shift ◽  
Transition Rates ◽  
Distance Method ◽  
Doppler Shift Attenuation ◽  
Theoretical Predictions ◽  
Γ Rays ◽  
Recoil Distance

The T(16O,p)18O reaction has been employed to measure the lifetimes of the 1.98 MeV 2+ level (τ = 3.35 ± 0.20 ps) and the 3.55 MeV 4+ level (τ = 24.5 ± 3.3 ps) of 18O by the recoil distance method. The lifetime of the 1.89 MeV 2+ level of 18Ne (τ = 0.63 ± 0.13 ps) has been measured by observing the Doppler shift attenuation of γ rays from 18Ne ions recoiling from the 16O(3He,n) reaction into Y and Ta backings. Transition rates in these mirror nuclei are compared with theoretical predictions.

Lifetimes and branching ratios of energy levels of 28Si. I

1969 ◽  
Vol 47 (6) ◽  
pp. 639-649 ◽  
Author(s):  
A. E. Litherland ◽  
P. J. M. Smulders ◽  
T. K. Alexander
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Energy Levels ◽  
Ground Level ◽  
Particle Beam ◽  
High Energy ◽  
Branching Ratios ◽  
Alpha Particles ◽  
Doppler Shift Attenuation ◽  
Energy Gamma

The gamma rays from the 25Mg(α,nγ)28Si reaction have been studied using alpha particles with energies ranging from 4.8 to 6.0 MeV. A 25 cm3 Ge(Li) gamma-ray counter was used to observe the complex high energy gamma-ray spectra at angles between 0° and 130° to the alpha-particle beam. Estimates of the nuclear lifetimes of the energy levels excited were obtained from Doppler shift attenuation measurements. The de-excitation branching ratios of the levels were also measured. The existence of a new level in 28Si at 6695 keV was confirmed. The recently reported 3− level at either 6880 keV or 6889 keV was observed and found to be the 6880-keV member of the doublet. The enhancement of the octupole transition to the ground level of 28Si was found to be 13 Weisskopf units.

Study of the Decay of the 3.696 MeV Level in 25Al

1971 ◽  
Vol 49 (4) ◽  
pp. 467-474 ◽  
Author(s):  
G. J. McCallum ◽  
R. J. Sparks ◽  
G. E. Coote ◽  
K. P. Pohl
Keyword(s):  
Doppler Shift ◽  
Gamma Ray ◽  
Branching Ratios ◽  
Angular Distributions ◽  
Doppler Shift Attenuation ◽  
Doppler Shift Attenuation Method

The decay of the 3.696 MeV level in 25Al has been studied by means of the 24Mg(p,γ)25Al reaction at the 1.49 MeV resonance. Gamma-ray branching ratios, direct angular distributions, and lifetimes determined by the Doppler shift attenuation method are reported.

An examination of Doppler shift attenuation factors and lifetimes for excited nuclear states in 59Cu and 63Cu

1980 ◽  
Vol 58 (3) ◽  
pp. 359-362 ◽  
Author(s):  
B. E. Cooke ◽  
J. R. Leslie ◽  
W. McLatchie ◽  
P. Skensved
Keyword(s):  
Energy Loss ◽  
Excited States ◽  
Doppler Shift ◽  
Speed Of Light ◽  
Proton Capture ◽  
Doppler Shift Attenuation ◽  
Resonance Strengths ◽  
Γ Rays ◽  
Standard Energy ◽  
Existing Data

Excited states in 59Cu and 63Cu have been studied with radiative proton capture. Doppler shift attenuation factors have been measured for γ-rays depopulating these states, with ion recoil speeds of approximately 0.1% of the speed of light. Measurements of resonance strengths reported here, together with existing data from other techniques, have been used to deduce lifetimes for the same states. For five cases where the DSA factors and the lifetimes have been determined independently, consistency with DSAM theory is optimized when the standard energy loss value is multiplied by a factor of 0.94 ± 0.11.

Gamma rays from the 3702 keV level in 25Al

1969 ◽  
Vol 47 (23) ◽  
pp. 2609-2619 ◽  
Author(s):  
N. Anyas-Weiss ◽  
A. E. Litherland
Keyword(s):  
Angular Distribution ◽  
Lower Limit ◽  
Gamma Rays ◽  
Doppler Shift ◽  
Gamma Ray ◽  
Decay Modes ◽  
Mirror Nucleus ◽  
Mixing Ratios ◽  
Doppler Shift Attenuation ◽  
Decay Gamma

The decay modes of the 7/2−, 3702 keV level in 25Al have been studied at the Ep = 1490 keV resonance in the 24Mg(p,γ)25Al reaction. The decay gamma rays were observed using a 25 cm3 Ge(Li) detector. A previously unreported 2% transition from the resonance to the level at 2723 keV has been observed. The angular distribution of this gamma ray admits only a spin of 7/2 for the 2723 keV level. The lifetime of the 2723 keV level was measured with the Doppler shift attenuation method (DSAM) at the 1660 keV resonance and was found to be [Formula: see text]. The lifetime of the 5/2+, 1790 keV level has been measured using the DSAM and has been found to be [Formula: see text]. From Doppler shift measurements a lower limit for the lifetime of the 3/2+, 945 keV level of [Formula: see text] was obtained. From angular distribution measurements at the Ep = 1490 keV resonance, the following multipole mixing ratios have been measured: δ(R → 0) = 0.00 ± 0.02; δ(R → 1790) = −0.02 ± 0.02; δ(R → 2723) = 0.15 ± 0.30; [Formula: see text]; δ(1790 → 945) = −0.15 ± 0.05; δ(945 → 0) = 0.35 ± 0.10 or 1.7 ± 0.2; δ(945 → 451) = −0.15 ± 0.05 or 2.6 ± 0.4. Comparisons with data in the mirror nucleus 25Mg have been made.

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