Behaviour of Prompt Gamma-Ray Emission in ColdFission of 252Cf

The behaviour of prompt γ-ray emission in the cold fission of ²⁵²Cf was investigated experimentally using a four-parameter correlation technique. A twin gridded ionization chamber was employed to detect the fission signals and to determine the fragment emission angles, and a φ10cm×10cm NaI(T1) detector was used to record the γ-ray energies. The result shows that the angular distribution coefficient of γ-rays emitted in cold fission is twice as large as that in the normal fission.The fact that in the cold fission the number of γ-rays emitted from the light fragments is approximately three times as large as that from the heavy ones can not be explained satisfactorily so far.     

Evaluation of the 1077 keV γ-ray emission probability from 68Ga decay

⁶⁸Ga decays to the excited states of ⁶⁸Zn through the electron capture decay mode. New recommended values for the emission probability of 1077 keV γ-ray given by the ENSDF and DDEP databases all use data from absolute measurements. In 2011, JIANG Li-Yang deduced a new value for 1077 keV γ-ray emission probability by measuring the ⁶⁹Ga(n,2n) ⁶⁸Ga reaction cross section. The new value is about 20% lower than values obtained from previous absolute measurements and evaluations. In this paper, the discrepancies among the measurements and evaluations are analyzed carefully and the new values are re-recommended. Our recommended value for the emission probability of 1077 keV γ-ray is (2.72± 0.16)%.     

Decay of the compound nucleus 74Kr formed in the reaction 16O + 58Ni

Gamma-ray and charged-particle emission has been studied after bombardment of ⁵⁸Ni with ¹⁶O at energies from 44.5–76.5 MeV. The excitation functions for various reaction channels have been measured. The locus in energy and spin of maximum cross section (the entry line) of the γ-emitting region in the 2pγ and 3pγ channels have been studied through measurement of γ-ray multiplicity, average particle energy and average γ-ray energy. The standard deviations in both energy and spin of the distributions of cross section are presented. Statistical model calculations including shell corrections in the level density show very satisfactory agreement with the experimental results. The moment of inertia at high spin and excitation energy is deduced from the measured entry line.     

Gamma-Ray Pulsars

Based on Arons and Scharlemann model, the mechanism of γ-ray emission of pulsars is discussed. The criterion for radio pulsars appearing also as γ-ray pulsars is presented, after considering both dipole and quadrupole magnetic fields. The luminosities and fluxes of six known γ-ray pulsars are calculated. Using the criterion, twenty four possible candidates for γ-ray pulsars are listed and some characteristic quantities of them are also given.     

Anomalies of neutron and γ-ray emission in light charged particle accompanied fission of 252Cf

Correlations between the neutron and γ-ray emission and the kinetic energy of light charged particles (LCPs), such as protons, deuterons, tritons and alphas, from the fission of ²⁵²Cf were studied in a four parameter experiment. A ⊘ 16 cm × 5 cm liquid scintillator with n-γ discrimination and a ⊘ 10 cm × 10 cm NaI(Tl) crystal were employed to detect the neutrons and the γ rays, respectively, while a thin CsI(Tl) crystal, which had the ability to separate the LCPs, was used to determine the LCP energy. The experimental results show that for the α particle accompanied fission, the average total number of neutrons emitted per fission increases in the case of varying the alpha particle energy E_α from 7 to 11 MeV and then falls off linearly in a first approximation with increasing E_α, and the average total energy and the average total number of γ-rays per fission as well as the average γ-ray energy as functions of E_α show similar correlation features. For the hydrogen-ion accompanied fission, the correlations of the neutron and γ-ray emission with hydrogen ion (t, d and p) energy are very similar to those for the alpha-particle accompanied fission. The correlations of the neutron and γ-ray emission in the low LCP energy region, in contrast to that observed in the high LCP energy range, are called anomalies. On the basis of the results obtained by the three-point charge model and the liquid drop model calculation with shell and pairing correction, the anomalous behavior of the neutron and γ-ray emission is explained tentatively.     

Study of the high-energy part of the spectrum of γ rays from the neutron-induced fission reaction of 235U nuclei

The spectrum of γ rays from the neutron-induced fission reaction of ²³⁵U nuclei has been investigated in the energy range 10–90 MeV. The experiment was performed in the horizontal channel of a nuclear reactor. The energy spectra was measured using a single-crystal NaI(Tl) spectrometer. The data on the energy dependence of the yield of γ rays have been obtained in the energy range 10–36 MeV. The upper limit of the probability of γ-ray emission has been determined for the range 36–90 MeV.     

The neutron binding energy in the neutron-rich nucleus93Sr

The neutron binding energy in⁹³Sr has been determined to (5230±6) keV from energy correspondences between levels defined by γ-ray transitions and β-delayed neutron emission.     

BL Lac天体的γ射线和射电辐射的统计特性

给出了一个带有射电5.0GHz,8.4GHz 和γ射线辐射流量密度的22个γ噪BL Lac天体的样本,研究了它们在1GeV处的γ射线辐射流量密度最大值、平均值及最小值与射电5.0GHz,8.4GHz辐射流量之间的可能关系.结果表明：1）射电5.0GHz,8.4GHz辐射与γ射线辐射在低态时没有相关,但在高态和平均态时都存在较强的相关,最大相关系数r=0.85,置信度均好于10^-4;2）γ射线谱指数和射电谱指数之间也有一个弱相关关系存在.因此,认为γ射线的辐射主要是同步自康普顿辐射. 关键词： BL Lac天体 γ射线 射电辐射 谱指数     

用离散相关函数方法分析Blazar天体的γ射线和射电辐射的相关性

收集了119颗有γ射线噪的Blazar天体样品(97个平谱射电类星体和22个BL Lac天体)，用离散相关函数(DCF)方法分析了1GeV γ射线辐射流量(最大值、最小值和平均值)与8.4GHz射电辐射流量之间的相关性.获得的主要结果为：在119个Blazar天体和97个平谱射电类星体中，γ射线辐射流量的最大值以及平均值和射电辐射流量之间有相关性;而γ射线辐射流量的最小值和射电辐射流量之间没有相关性.本文结果表明，γ射线和射电辐射都来自喷流，γ射线很可能产生于同步自康普顿(SSC)过程. 关键词： Blazar γ射线 射电辐射 流量密度     

Effect of γ-irradiation on structural,morphological and luminescence properties of cerium-doped Y3Al5O12 nano-material

ABSTRACT

Cerium-doped yttrium aluminum garnet (YAG: Ce³⁺) nanopowder phosphors have been elaborated by sol–gel process and annealed at 900°C for 2?h. The prepared phosphors were exposed to gamma radiation, using ⁶⁰Co source, at different doses ranging from 5 to 100?kGy. The influence of γ-irradiation on the structural, morphological and luminescence properties of YAG: Ce³⁺ phosphors were investigated in detail by X-ray diffraction, ?eld emission scanning electron microscopy (FESEM), Fourier transforms infrared spectroscopy (FTIR) and photoluminescence measurements. The XRD analysis confirmed the presence of single cubic phase for all samples of YAG: Ce³⁺ nanophosphors independent of γ-rays dose. FESEM micrograph results revealed that the particles present flate-like shapes and high density of dislocation for sample irradiated at 100?kGy of γ-ray. The YAG: Ce³⁺ nanophosphors showed broad green–yellow emission band in the range of 450–700?nm with maximum intensity at 538?nm assigned to the 5d → 4f transitions of Ce³⁺ ion. The emission intensity of YAG: Ce³⁺ phosphors vary with the γ-ray irradiation and reach the maximum for sample irradiated to a dose of 25?kGy. The variation of luminescence intensity is related to the crystallite size and Ce⁴⁺ ions content in YAG host nanomaterial.     

The deuteron binding energy

The ¹H(n, γ)²H γ-ray energy has been measured relative to ⁴⁸V and ¹⁴⁴Ce γ-rays, which are both based on the gold standard for γ-ray energies. The ensuing deuteron binding energy, $\text{B(}{}^2\text{H}\text{= 2224575 ± 9}\text{eV}$, confirms (with higher accuracy) the value from one of two conflicting recent precision measurements. This value has been used to recalculate the energies of γ-rays from thermal-neutron capture in ²H, ¹²C, ¹³C and ¹⁴N, which serve as mass-based γ-ray energy standards.     

Isomer ratio measurements for the reaction 29Si(18O,p2n)44m, 44gSc

Isomer ratios for the reaction ²⁹Si(¹⁸O, p2n)^44gSc, ^44gSc have been deduced from activity measurements for projectile energies between 30 and 99 MeV. Statistical model calculations show that the isomer ratio dependence on projectile energy up to about 80 MeV can be adequately described by assuming a fixed ratio of quadrupole to dipole γ-ray strengths. Such a ratio of E2/E1 strengths agrees with corresponding values deduced from the literature. The values of the γ-ray strength ratios needed to fit the experimental isomer ratios are extremely sensitive to the relative amounts of quadrupole γ-ray admixture and to the presence of discrete levels other than those which conform to the yrast line.     

Cross section of metastable state population in the photoneutron decay of the E1 giant resonance for 110Pd, 112Cd, and 113In nuclei

The cross sections of isomeric state excitation in the ¹¹⁰Pd(γ, n)^109m Pd, ¹¹²Cd(γ, n)^111m Cd, and ¹¹³In(γ, n)^112m In reactions have been investigated. The measurements were performed in the γ-ray energy range 9–18 MeV with a step ΔE = 0.5 MeV. The dependences of the isomeric ratios on the γ-ray energy are obtained. The experimental data are compared with the results of calculations within the cascade-evaporation model.     

Delayed neutrons and high-energy γ-rays from decay of 87Br

Delayed neutrons and high-energy γ-rays following decay of ⁸⁷Br have been studied to characterize the β-decay to and the decay of neutron unbound levels in ⁸⁷Kr. The principal part of the neutron spectrum appears due to some 20–30 individual transitions and for seven of these, decay by γ-ray emission has been demonstrated. The β-strength function derived from these data and the decay scheme at lower energies is dominated by a broad resonance located near the neutron binding energy which can be identified with the main strength of a single-particle transition. The fluctuations in the reduced β-transition probabilities are found to be in accord with the Porter-Thomas distribution and the observed level density just above the neutron binding energy is consistent with the Gilbert and Cameron prediction after accounting for fluctuation in the β-decay transition probabilities.     

Investigation of giant E3 resonances by (N, γ) reactions

Effects related to the presence of giant E3 resonances are investigated by nucleon radiative capture according to the direct-semidirect model. The γ-ray angular distributions from the ²⁰⁸Pb(N, γ₀) reactions are calculated in the energy region above the giant dipole resonance and the influence of the E1–E3 and E2–E3 interferences is discussed. The results provide indications of an appreciable effect on the 90° photon emission when a collective isovector E3 excitation is present.     

Fabrication and Gamma-Ray Irradiation Effect on Optical and Mechanical Properties of Germano-Silicate Glass Fibers with Inner Cladding of B and F Doped Silica Glasses

ABSTRACT

The effect of glass composition, pure silica glass, boron-doped and fluorine-doped silica glasses of inner cladding, in the germano-silicate glass core fibers on optical and mechanical properties upon the γ-ray irradiation was investigated. Enhanced radiation hardening at 1,550 nm was found in both the B- and F-doped fibers after the γ-ray irradiation with dose-rate of 1.25 kGy/h. The radiation-induced attenuation (RIA) was found to increase in the order of the B-doped fiber, the F-doped fiber, and the silica fiber. While no major influence on the refractive index of the fibers after the γ-ray irradiation was found, the residual stress was slightly changed.     

Relative population of the oblate and prolate structures in187Au

The population of the oblate and the prolate structures in¹⁸⁷Au has been studied using the “Château de Cristal” set-up through the¹⁷²Yb(¹⁹F, 4n) reaction at 90, 95 and 100 MeV beam energy. γ — γ, γ-Fold and γ -Sum energy coincidence measurements were performed, γ-ray intensity measurements showed that as the beam energy increases the prolate system is less populated than the oblate one. Fold and Sum-energy associated with oblate and prolate structures showed a different behaviour with increasing beam energy. Two mechanisms are suggested to explain these results.     

The γ-ray spectrum following the β−-decay of147Nd

The still existing discrepancies in the γ-ray spectrum accompanying the β^?-decay of¹⁴⁷Nd could be cleared up by careful measurements with high-resolution Ge(Li)-detectors. It could be shown that these discrepancies are caused by radioactive impurities of^148m Pm thus excluding several energy levels and γ-ray transitions reported in earlier papers. The experimental level scheme is compared with the predictions of intermediate coupling theory.     

Low-energy break in the spectrum of Galactic cosmic rays

Measurements of the low-energy spectrum of Galactic cosmic rays (GCRs) by detectors on or near Earth are affected by solar modulation. To overcome this difficulty, we consider nearby molecular clouds as GCR detectors outside the Solar System. Using γ-ray observations of the clouds by the Fermi telescope, we derive the spectrum of GCRs in the clouds from the observed γ-ray emission spectrum. We find that the GCR spectrum has a low-energy break with the spectral slope hardening by ΔΓ=1.1±0.3 at an energy of E=9±3 GeV. Detection of a low-energy break enables a measurement of GCR energy density in the interstellar space U=0.9±0.3 eV/cm{3}.