Lifetimes and decay modes of low-lying levels in 26Mg and 26Al

1968 ◽  
Vol 46 (9) ◽  
pp. 1035-1050 ◽  
Author(s):  
O. Häusser ◽  
T. K. Alexander ◽  
C. Broude
Keyword(s):  
Excitation Energy ◽  
Excited States ◽  
Gamma Rays ◽  
Doppler Shift ◽  
Bound States ◽  
Branching Ratios ◽  
Decay Modes ◽  
Rotational Bands ◽  
Decay Properties

Several bound states with excitation energy up to 7 MeV were studied in 26Mg, using the 26Mg(p, p′γ) reaction. The attenuated Doppler shift of the de excitation gamma rays was observed with a Ge(Li) spectrometer. The extracted lifetime estimates and branching ratios for 15 excited states suggest that the rotational bands, built on different intrinsic states, are mixed considerably. Incidental information on lifetimes and decay properties of states in 26Al is also presented.

The 23Na(α,γ)27Al reaction. A survey of the reaction and some properties of the 27Al nucleus

1969 ◽  
Vol 47 (15) ◽  
pp. 1545-1555 ◽  
Author(s):  
H. Röpke ◽  
N. Anyas-Weiss
Keyword(s):  
Excitation Energy ◽  
Excited States ◽  
Bound States ◽  
Branching Ratios ◽  
Angular Distributions ◽  
Particle Capture ◽  
Excitation Energies ◽  
Decay Modes ◽  
Γ Ray ◽  
27Al Reaction

The 23Na(α,γ) reaction has been studied in the region Eα = 2–3 MeV. The γ-ray spectra from a total of 16 resonances have been surveyed using a 40 cm3 Ge(Li) detector. Excitation energies, γ-ray decay modes, branching ratios, and γ-ray yields of these resonances are given. Below Eα = 2.7 MeV, all resonances have [Formula: see text] and the α-particle capture proceeds with [Formula: see text]. The resonances at Eα = 2.696 and 2.797 MeV have strong branches to the Jπ = 11/2+ state in 27Al at 4.509 MeV excitation energy. A measurement of γ-ray angular distributions at these resonances yields Jπ(2.969 res.) = 9/2+, 11/2 and Jπ(2.797 res.) = 9/2+ for the resonances, and Jπ(5.671) = 9/2+, 7/2 and Jπ(4.580) = 9/2+, 7/2 for bound states in 27Al. Investigation of this latter level at the Ep = 2.114 MeV resonance in the 26Mg(p,γ)27Al reaction restricts the spin to 7/2. New excited states in 27Al were found at Ex = 5.504, 5.671, and 7.815 MeV. A state at Ex = 5.499 MeV was confirmed.

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.

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.

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.

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.

Decay of 142La

1971 ◽  
Vol 49 (9) ◽  
pp. 1179-1185 ◽  
Author(s):  
S. L. Tong ◽  
W. V. Prestwich ◽  
K. Fritze
Keyword(s):  
Excited States ◽  
Beta Decay ◽  
Gamma Rays ◽  
Proportional Counter ◽  
Decay Scheme ◽  
Branching Ratios ◽  
Coincidence Measurement

The energies of the gamma rays following the beta decay of 92.5 min 142La have been precisely measured, and a coincidence measurement with a NaI(Tl) and Ge(Li) system was made by gating the NaI(Tl) at 641 keV. With these results, the decay scheme of 142Ce derived by Prestwich and Kennett was modified. The beta branching ratios of the decay of 142La to the ground and excited states of 142Ce have also been obtained by simultaneous gamma and 4π beta countings with a 3 in. × 3 in. NaI(Tl) detector and a 4π-proportional counter.

LOW-SPIN STATES OF 83Rb EXCITED IN THE 83Sr(β++EC)83Rb DECAY

2000 ◽  
Vol 09 (06) ◽  
pp. 471-485 ◽  
Author(s):  
XIAOHAN YU ◽  
SHUANGHUI SHI ◽  
JIAHUI GU ◽  
JINGYI LIU ◽  
WENXIN LI ◽  
...  
Keyword(s):  
Excited States ◽  
Gamma Rays ◽  
Half Life ◽  
Beam Energy ◽  
Decay Scheme ◽  
Branching Ratios ◽  
Spin States ◽  
New Information ◽  
Hpge Detectors ◽  
Γ Ray

Gamma-rays from the 83 Sr (β++ EC )83 Rb decay have been investigated with Compton suppressed HpGe detectors. The activity was produced via the 85 Rb (p,3n) reaction at 27.1 MeV beam energy. Singles in multispectra mode and γ–γ coincidence experiments were performed. Approximately 190 transitions including 94 new transitions and 19 new levels were assigned to 83 Rb , based on their measured half-life and/or observation in coincidence with well-known lines. A decay scheme has been constructed consisting of 41 excited states and 180 transitions in 83 Rb . Additional new information has been obtained on γ-ray branching ratios, log ft values, spins and parities.

GAMMA-RAY TRANSITIONS IN 15O AND 15N

1965 ◽  
Vol 43 (12) ◽  
pp. 2310-2318 ◽  
Author(s):  
T. K. Alexander ◽  
A. E. Litherland ◽  
C. Broude
Keyword(s):  
Excited States ◽  
Gamma Rays ◽  
Doppler Shift ◽  
Gamma Ray ◽  
Measured Energy ◽  
The Mean ◽  
The Difference ◽  
Mean Lifetimes

The gamma rays from the first two excited states of 15O and 15N populated by the 14N + d, T(16O, αγ)15N, and 16O(3He, αγ)15O reactions have been observed with a Ge(Li) spectrometer. The measured energy separations are 50 ± 5 keV for the 15O doublet and 28.5 ± 3 keV for the 15N doublet. The difference between the 5.24-MeV gamma ray from 15O and the 5.27-MeV gamma ray from 15N is 29 ± 1 keV. From Doppler-shift and broadening measurements of the energies of the gamma rays from the T(16O, αγ)15N and 16O(3He, αγ)15O reactions, information on the mean lifetimes of the states was obtained. The mean lifetimes of the 5.30-and 5.27-MeV states of 15N are 4.3 ± 1.8 × 10−14 sec and > 10−12 sec respectively. The mean lifetimes of the 5.19- and 5.24-MeV states of 15O are < 3 × 10−13 sec and > 10−12 sec respectively.

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.

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