THE ANGULAR DISTRIBUTION OF 5.6-MeV GAMMA RAYS FROM THE CAPTURE BY 124Sn OF 62-eV NEUTRONS

1965 ◽  
Vol 43 (12) ◽  
pp. 2156-2161 ◽  
Author(s):  
K. G. McNeill ◽  
D. B. McConnell ◽  
F. W. K. Firk
Keyword(s):  
Angular Distribution ◽  
Gamma Rays ◽  
Ground State ◽  
Gamma Ray ◽  
The State

Angular distribution measurements have been made on the near-ground-state gamma-ray transitions from the state in 125Sn excited by the capture by 124Sn of 62-eV neutrons. The distribution is essentially isotropic. In conjunction with other evidence, it is concluded that the capturing state is a p 1/2 state.

Proton?Capture Gamma Rays from Nitrogen?13

1962 ◽  
Vol 15 (3) ◽  
pp. 443 ◽  
Author(s):  
AW Parker ◽  
GG Shute
Keyword(s):  
Angular Distribution ◽  
Excited State ◽  
Elastic Scattering ◽  
Gamma Rays ◽  
Ground State ◽  
Recent Experiment ◽  
Gamma Ray ◽  
Angular Distributions ◽  
Proton Capture ◽  
Yield Curves

From a recent experiment in this laboratory (Shute et al. 1962) on the elastic scattering of protons from 12C, resonance levels (E13N, J1t) of 13N were obtained at the laboratory bombarding energies (Ep) shown in Table 1. To confirm these results, an investigation of the yield and angular distribution of gamma rays from the reaction 12C(p'YO)13N and 12C(p'Yl)13N was undertaken. Accordingly, the theoretical angular distributions, W(8), for the gamma ray (Yo) to the ground state of 13Na-) and also for the gamma ray (Yl) to the 1st excited state of 13Na+) were evaluated on the assumptions that overlap of levels in 13N is small and lowest order multipoles are involved. As angular distributions are parity insensitive, these were found to be identical for the two gamma rays expected. The simpler of these angular distributions are also shown on the table. The expected angular distributions indicate that 90� is a suitable angle for yield curves.

Study of Low-Lying Levels in 37Ar

1972 ◽  
Vol 50 (11) ◽  
pp. 1182-1194 ◽  
Author(s):  
P. Taras ◽  
A. Turcotte ◽  
R. Vaillancourt
Keyword(s):  
Angular Distribution ◽  
Gamma Rays ◽  
Linear Polarization ◽  
Ground State ◽  
Solar Neutrino ◽  
Gamma Ray ◽  
Capture Rate ◽  
Mixing Ratio ◽  
Excitation Energies ◽  
Decay Gamma

The properties of the first five excited levels in 37Ar were investigated via the 37Cl(p,n)37Ar reaction at Ep = 3.98, 4.17, 4.38, and 4.81 MeV and via the 34S(α,n)37Ar reaction at Eα = 8.00, 8.50, and 8.60 MeV. The following excitation energies were obtained: Ex = 1409.7 ± 0.4, 1611.5 ± 0.4, 2217.8 ± 0.8, 2491.4 ± 0.8, and 2797.0 ± 0.8 keV. These levels were found to decay almost entirely to the ground state. The angular distribution and the linear polarization of the decay gamma rays of these levels were measured. From these measurements definite spin–parity assignments as well as values of the mixing ratio of the ground state gamma-ray transitions were obtained. These are: Ex(Jπ, δ) = 1612 ([Formula: see text], +0.11 ± 0.02), 2218 ([Formula: see text], 0.0 ± 0.02), 2491 ([Formula: see text]), and 2797 ([Formula: see text], −0.16 ± 0.03 or +8.0 ± 1.5, the value of −0.16 being more probable). The measurements were also consistent with a spin of [Formula: see text] for the 1410 keV level. The results are compared with a recent shell-model calculation and are discussed in the context of the solar neutrino capture rate in 37Cl.

High-Purity Germanium Technology for Gamma-Ray and X-Ray Spectroscopy

1993 ◽  
Vol 302 ◽  
Author(s):  
L.S. Darken ◽  
C. E. Cox
Keyword(s):  
Cross Section ◽  
Gamma Rays ◽  
Ground State ◽  
High Purity ◽  
Gamma Ray ◽  
Capture Rate ◽  
X Rays ◽  
Hole Capture ◽  
High Purity Germanium ◽  
Energy Gamma

ABSTRACTHigh-purity germanium (HPGe) for gamma-ray spectroscopy is a mature technology that continues to evolve. Detector size is continually increasing, allowing efficient detection of higher energy gamma rays and improving the count rate and minimum detectable activity for lower energy gamma rays. For low-energy X rays, entrance window thicknesses have been reduced to where they are comparable to those in Si(Li) detectors. While some limits to HPGe technology are set by intrinsic properties, the frontiers have historically been determined by the level of control over extrinsic properties. The point defects responsible for hole trapping are considered in terms of the “standard level” model for hole capture. This model originates in the observation that the magnitude and temperature dependence of the cross section for hole capture at many acceptors in germanium is exactly that obtained if all incident s-wave holes were captured. That is, the capture rate is apparently limited by the arrival rate of holes that can make an angular-momentum-conserving transition to a s ground state. This model can also be generalized to other materials, where it may serve as an upper limit for direct capture into the ground state for either electrons or holes. The capture cross section for standard levels σS.L. is given bywhere g is the degeneracy of the ground state of the center after capture, divided by the degeneracy before capture. Mc is the number of equivalent extrema in the band structure for the carrier being captured, mo is the electronic mass, m* is the effective mass, and T is the temperature in degrees Kelvin.

Properties of the 1.410 and 1.612 MeV Levels in 37Ar and the 1.727 MeV Level in 37Cl

1971 ◽  
Vol 49 (9) ◽  
pp. 1215-1224 ◽  
Author(s):  
P. Taras ◽  
A. Turcotte ◽  
R. Vaillancourt ◽  
J. Matas
Keyword(s):  
Angular Distribution ◽  
Gamma Rays ◽  
Linear Polarization ◽  
Single Particle ◽  
Ground State ◽  
Incident Proton ◽  
Mixing Ratio ◽  
Single Particle Excitation ◽  
Decay Gamma

The properties of the 1.410 and 1.612 MeV levels in 37Ar and the 1.727 MeV level in 37Cl were investigated. The levels in 37Ar were populated via the 37Cl(p,n)37Ar reaction and the level in 37Cl via the 37Cl(p,p′)37Cl reaction. The angular distribution and the linear polarization of the decay gamma rays of these levels were measured at incident proton energies of 3.98, 4.17, 4.38, and 4.81 MeV. The results of these measurements are consistent with a spin of 1/2 for the 1.410and 1.727 MeV levels, while they definitely establish the spin and parity of the 1.612 MeV level to be 7/2−. This last level has also been found to decay entirely to the ground state, with a multipolarity mixing ratio δ(E3/M2) = +0.22 ± 0.11. This level has properties quite similar to those of the 7/2− states in 35Cl and 37Cl, indicating that they may all arise from a 1f7/2 single-particle excitation.

scholarly journals Separating astrophysical sources from indirect dark matter signals

2014 ◽  
Vol 112 (40) ◽  
pp. 12272-12277 ◽  
Author(s):  
Jennifer M. Siegal-Gaskins
Keyword(s):  
Dark Matter ◽  
Angular Distribution ◽  
Energy Spectrum ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Dark Matter Annihilation ◽  
Robust Identification ◽  
Analysis Methods ◽  
The Status

Indirect searches for products of dark matter annihilation and decay face the challenge of identifying an uncertain and subdominant signal in the presence of uncertain backgrounds. Two valuable approaches to this problem are (i) using analysis methods which take advantage of different features in the energy spectrum and angular distribution of the signal and backgrounds and (ii) more accurately characterizing backgrounds, which allows for more robust identification of possible signals. These two approaches are complementary and can be significantly strengthened when used together. I review the status of indirect searches with gamma rays using two promising targets, the Inner Galaxy and the isotropic gamma-ray background. For both targets, uncertainties in the properties of backgrounds are a major limitation to the sensitivity of indirect searches. I then highlight approaches which can enhance the sensitivity of indirect searches using these targets.

THE ANGULAR DISTRIBUTION OF GAMMA RAYS IN THE C12(p,p′γ) REACTION

1953 ◽  
Vol 31 (2) ◽  
pp. 189-193 ◽  
Author(s):  
H. E. Gove ◽  
N. S. Wall
Keyword(s):  
Angular Momentum ◽  
Angular Distribution ◽  
Excited State ◽  
Proton Beam ◽  
Gamma Rays ◽  
Ground State ◽  
Expansion Formula ◽  
First Excited State ◽  
Incoming Proton

Protons of 7.1 Mev. energy from the MIT cyclotron have been used to investigate the angular distribution of gamma rays from the C12(p,p′γ) reaction with respect to the incoming proton beam. These gamma rays result from transitions between the first excited state of C12 at 4.45 Mev. and the ground state. The resulting distribution can be fitted by the expansion[Formula: see text]which is consistent with an assignment of two for the angular momentum of the first excited state of C12.

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.

High-resolution gamma-ray study of 185Wm

1970 ◽  
Vol 48 (5) ◽  
pp. 502-510 ◽  
Author(s):  
S. C. Gujrathi ◽  
J. M. D'auria
Keyword(s):  
High Resolution ◽  
Gamma Rays ◽  
Ground State ◽  
Internal Conversion ◽  
Gamma Ray ◽  
X Ray ◽  
Isomeric Level ◽  
Coincidence System ◽  
Internal Conversion Coefficients ◽  
Conversion Coefficients

The decay of 185Wm has been investigated using a high-resolution Ge(Li) X-ray spectrometer and a Ge(Li)–NaI(Tl) coincidence system. The energies and relative intensities (given in parentheses) of the observed gamma rays associated with the decay of the 185Wm (T1,2 = 1.68 min) are: 23.54 (3.3), 42.29 (1.1), 65.857 (100), 93.30 (0.5), 94.59 (2.2), 107.850 (6.8), 122.05 (1.5), 131.554 (84.0), 164.334 (11), 173.675(61.5),and 187.879(15.4) keV. The energy of the isomeric level has been deduced to be 197.41 keV and decays to the ground state through levels at 187.88, 173.68, 93.29, 65.86, and 23.54 keV. In addition, it was deduced experimentally from measured internal-conversion coefficients that the multipolarity of the 131.55 keV transition is E3 while the 65.86 keV transition is an M1 + E2 mixture with a 30 ± 7.5% M1 component.

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.

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