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1.
Estimates obtained for the average atomic number 〈lnA〉 of nuclei of primary particles with energies in the region of E 0 ? 1015 eV over the past 36 years at the Yakutsk array and other arrays worldwide for studying extensive air showers are presented. It is shown that these estimates are markedly different with in different time periods. Earlier than 1996, the composition of cosmic rays in the energy range of 5 × 1015–1018 eV was markedly lighter than in later years. After 2008, there appeared a trend toward a decrease in 〈lnA〉. This is likely to be a manifestation of some explosive process in the Milky Way Galaxy after 1996.  相似文献   

2.
The complicated shape of the cosmic ray spectrum recorded by giant arrays in the energy range 1017–1020 eV is analyzed. It is shown that in the energy region ∼1018–1019 eV the spectrum probably coincides with the injection spectrum whose exponent is equal approximately to 3.2–3.3. The flatter component in the energy region (3.2–5.0)×1019 eV is due to braking of extragalactic protons on primordial photons (the cosmic background radiation). At energies exceeding 3.2×1019 eV the spectrum does not have a blackbody cutoff. The possibility of determining the distances at which cosmic rays originate and investigating the evolution of their sources on the basis of ultrahigh-energy cosmic ray data is discussed. Zh. éksp. Teor. Fiz. 113, 12–20 (January 1998)  相似文献   

3.
Self-assembled arrays of Ge-Si clusters with sizes of ~ 10 nm and a density of ~ 1010 cm?2 have been grown by molecular beam epitaxy. Stable steady-state field electron emission from such clusters has been observed and studied. The emission is characterized by resonance current peaks, which are explained by the quantization of the electron energy in nanoclusters. The estimation of the ground level energy from their emission measurements coincides with estimates obtained by other methods.  相似文献   

4.
A. V. Uryson 《JETP Letters》1997,65(10):763-767
The complicated form of the cosmic-ray spectrum recorded in the energy range 1017–1020 eV by giant detector arrays is analyzed. It is shown that the spectrum in the region 1018–1019 eV is apparently identical to the injection spectrum with power-law exponent approximately equal to 3.2–3.3. The flat component in the region (3.2–5)×1019 eV is due to the braking of extragalactic protons by relict photons. The spectrum apparently has no blackbody cutoff at energies above 3.2×1019 eV. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 10, 729–733 (25 May 1997)  相似文献   

5.
There falls on the Earth's atmosphere a rain of particles and photons the high energy part of which is termed the Cosmic Radiation. This article is concerned specifically with primary particles of the highest known energies, i.e. 1017-1020eV and deals with the evidence for their existence, their nature and their origin.

Such particles are very rare but because they produce many millions of secondaries in the atmosphere they can be readily detected by large counter arrays at ground level. Some of the principal arrays in the world will be described including the giant array at Haverah Park, near Harrogate, England. The latest results on the energy spectrum and the incident directions of the primaries will be given and their astronomical significance critically assessed.

Finally, an account will be given of a novel array which promises to make a substantial contribution to our knowledge of primaries of energies even above 1020 eV.  相似文献   

6.
Data on muons with the threshold energy E μ≈1.0×secθ GeV in extensive air showers of energies E 0≥4×1016 eV measured on the Yakutsk and Akeno arrays are jointly analyzed. The results are compared with the calculations by the quark-gluon-string model with jets. It is shown that this model does not contradict the data measured for energies E 0≤1018 eV on both arrays under the assumption that the primary particle composition differs from the composition where heavy nuclei dominate over protons. Experimental data for energies E 0≥3×1018 eV indicate that the shower development differs from that predicted by the quark-gluon-string model with jets.  相似文献   

7.
A combination of three Fabry-Perot etalons with a small polychromator is used to measure wavelengths and line profiles of pulsed and cw-lasers. A small computer calculates from the interference fringe patterns monitored by silicon-diode arrays the wavenumber of laser lines within 0.002 cm-1. In case of pulsed lasers a single pulse with a minimum energy of 5 × 10-6 J is sufficient for wavelength determination.  相似文献   

8.
Several energy spectra of cosmic rays with energies E 0 ≥ 1017 eV measured at the Yakutsk EAS, AGASA, Haverah Park, HiRes, Auger, and SUGAR arrays are considered. It is shown that the fairly good mutual agreement of the spectrum shapes can be achieved if the energy of each spectrum is multiplied by a factor K specific for each spectrum. These factors exhibit a pronounced dependence on the latitude of the above-mentioned arrays.  相似文献   

9.
Summary The techniques for γ-ray astronomy at energies ≥10 TeV using air shower detectors are discussed. The results, based on a number of large arrays, are negative, with no point sources being identified. While the contributions to γ-ray astronomy so far have been only upper limits, these arrays in the future will make significant progress in the understanding of cosmic rays in the energy range 1013 eV to 1016 eV. Also, contributions to solar physics are being made by observations of shape and time dependence of the shadow of the Sun as observed in cosmic rays. For the advancement of γ-ray astronomy a greater sensitivity is required in the energy region of 10 TeV. A number of promising techniques to accomplish a greater sensitivity are discussed. They include the enlargement of the Tibet array at 4300 meters altitude, the array of open photomultipliers at La Palma (AIROBICC), which views the shower by the Cherenkov photons produced in the atmosphere, and the instrumentation of a pond at Los Alamos with photomultipliers (Milagro). Invited talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.  相似文献   

10.
This is a brief review of the investigations carried out by scientists from the Ioffe Physical-Technical Institute (St. Petersburg) within the framework of international projects for the study of the structure of high-spin nuclear states using heavy-ion beams and arrays of tens and hundreds of detectors for recording gamma rays and charged particles. The development and results of measurements of nuclear-level lifetime by Doppler techniques in the range 10?14–10?9 s are discussed.  相似文献   

11.
Time-resolved infra-red stimulated luminescence (TR-IRSL) technique enables an understanding of the dynamics of trapped electrons after IR excitation in the band-tail states of feldspar. This work intends to study the underlying physical mechanism of IRSL production. TR-IRSL studies were carried out on four feldspar mineral specimens of variable chemical composition and structural state. Assuming the IR excited trapped electrons make random walks in the band-tail states and recombine by tunnelling dynamically, hopping time is derived from the OFF time data of TR-IRSL. This analysis indicates that the hopping time decreases with stimulation temperature. Using Einstein diffusion equation, hopping probability is computed and is shown to obey the equation describing variable range hopping mechanism of Mott kind. Mott's parameters (hopping length and hopping energy) are then derived. Hopping length decreases with stimulation temperature whereas hopping energy increases with temperature. The average hopping length and energy are in the range of 11–18 Å and 45–55 meV respectively and the diffusion constant is estimated to be in the range of 10?10–10?9 cm2 s?1 for all the feldspar samples.  相似文献   

12.
In order to construct the energy spectrum on the basis of data from the Yakutsk array, a method similar to that employed at the AGASA array is applied in addition to the standard approach based on experimental procedures. Moreover, a new, original, method underlying the calculation of the spectrum in the region of energies above 1020 eV is used to estimate energies. In order to compare data obtained at different arrays, it is proposed to harness the universal spectrum based on HiRes data. Within the QGSJET2 model, it is shown that a shower of energy 2 × 1020 eV was observed at the Yakutsk array. In the same energy region (above 2 × 1020 eV), the AGASA array recorded four showers, while the Fly’s Eye array and Pierre Auger Observatory (PAO) recorded one shower each. These data do not confirm the conclusion that the flux of primary-cosmic-ray particles decreases because of the Greisen-Zatsepin-Kuzmin effect.  相似文献   

13.
The relative method was used to measure the photofission cross sections for 243Cm and 249Cf isotopes in the energy range from 6 to 12 MeV, for 245Cm in the energy range from 5 to 10 MeV, and for 249Bk in the energy range from 5.5 to 10 MeV. The measurements were performed with an energy step of 50 to 200 keV by using the microtron installed at the Institute of Physics and Power Engineering (Obninsk). The cross section for 238U photofission was used as a reference in these measurements. Data on the cross sections for 243Cm, 245Cm, and 249Bk photofission were obtained for the first time, while data on the cross section for 249Cf photofission were obtained for the first time only in the energyregion E<10 MeV. The data on the 245Cm nucleus suggest that, in the energy region around 6 MeV, the cross section for its photofission has a maximum, which is likely to be due to the low-energy resonance structure of the dipole-photoabsorption cross section. For 249Cf, an anomalously large value of the photo fission cross section is observed in the region of the first maximum of the giant dipole resonance (E≈11 MeV). By comparing the energy dependences obtained for the fissilities of the 243Cm and 249Bk isotopes from photofission data with the fissilities from direct-reaction data, it is found that the observed fission thresholds agree and that there is a plateau-like dependence at energies above 7.5 MeV. For the 245Cm and 249Cf nuclei, there are no similar data for performing such a comparison. Data on the fissilities as obtained from the present series of relative measurements that employ the microtron bremsstrahlung spectrum are analyzed.  相似文献   

14.
The differential energy spectrum of cosmic rays that is obtained on the basis of the measurements of Cherenkov radiation from extensive air showers in an energy range of 1015–1020 eV is compared with the model of the propagation of primary particles in the interstellar medium with fractal properties. It is found that the shape of the experimental spectrum is in good agreement with the shape of the calculated spectrum of “all particles” at 1015–1018 eV. The average mass composition of cosmic rays that is calculated on the basis of five components does not contradict the average mass composition obtained from the experimental data for several parameters in this energy range.  相似文献   

15.
The adsorption of Xe and CO on Ag(111) in the range 66 to 123 K and 10?7 to 10?1 Pa has been studied by surface potential, low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and electron energy loss spectroscopic (EELS) measurements. Isotherms derived from both surface potential and AES measurements for submonolayer Xe adsorption reveal successive stages and a two-dimensional phase change. Isosteric heats were 18 ± 1 kJ mol?1. Temkin isotherms were observed for CO, the heat falling linearly with coverage from an initial value of 27 ± 1.5 kj mol?1. No ordered CO overlayer structure could be detected. EEL spectra of clean Ag(111) agree with previous studies. Additional loss peaks were recorded for Xe and CO overlayers, and the assignment of the substrate loss features is discussed in relation to the effects of adsorption.  相似文献   

16.
The yield of γ-rays from the reaction 42Ca(p, γ)43Sc has been measured as a function of bombarding energy over the range 0.63–3.01 MeV, from 44Ca(p, γ)45Sc over the range 0.775–4.00 MeV, from 42Ca(p, p'γ)42Ca over the range 2.24–3.01 MeV, and from 44Ca(p, p'γ)44Ca over the range 1.90–5.03 MeV. The cross section of the reaction 44Ca(p, n)44Sc has been measured from threshold to a bombarding energy of 5.05 MeV by observation of the 1157 keV γ-ray associated with the residual 44Sc activity, and the cross section of the reaction 45Sc(p, n)45Ti has been measured from threshold to a bombarding energy of 4.00 MeV both by observation of the annihilation radiation associated with the residual 45Ti activity and by measurement of the total neutron yield with a wide-angle BF3 tube and paraffin detector. All these data are compared with statisticalmodel calculations and satisfactory agreement is achieved. Thermonuclear reaction rates for the (p, γ) and (p, n) reactions are calculated for the temperature range 5 × 108-1010K and the significance of these results for explosive nucleosynthesis in stars is discussed.  相似文献   

17.
Boyi Zhou 《Molecular physics》2017,115(19):2442-2450
Quantum close-coupling computations of the rotational quenching of H2 and its isotopologues due to He impact are performed using a highly accurate potential energy surface. State-to-state cross sections are obtained in a wide range of collision energies between 10?5 cm?1 and 104 cm?1, and the theoretical rate coefficients are reported for temperatures ranging from 10?4 K to 3000 K. Compared with previous studies, the well depth of the potential adopted in this study is larger, leading to stronger resonance effects in the cross sections of He-HD. The accurate potential was employed to investigate the isotope effects of H2 in detail. The cross-section resonances shift towards lower collision energies and become stronger with increasing reduced mass. The calculated cross sections and rate coefficients of H2 and its isotopic variants in collisions with He are provided to study the energy transfer in these systems.  相似文献   

18.
The yield of γ-rays from the reaction 41K(p, γ)42Ca has been measured as a function of bombarding energy over the range 0.68–2.48 MeV and from the reaction 41K(p, αγ)38Ar over the range 1.20–2.48 MeV, and the yield of neutrons from the reaction 41K(p, n)41Ca has been measured from threshold to a bombarding energy of 2.48 MeV. The energy dependence of the cross sections is compared with statistical-model calculations with global optical-model parameters in all particle channels. The calculations seriously overestimate the cross section for the neutron channel and underestimate those for the other channels. A reduction in the imaginary well depth in the neutron channel leads to good agreement with all the data. Statistical-model calculations with this modified set of parameters are then carried out to provide cross sections for the astrophysically interesting reactions 41Ca(n, p)41K, 41Ca(n, α)38Ar, and 41Ca(n, γ)42Ca. Thermonuclear reaction rates are calculated for all six reactions over the temperature range 5 × 108–1010K which includes the range of temperatures of interest in nucleosynthesis calculations.  相似文献   

19.
The optical absorption spectra of an α-MnS single crystal and their temperature behavior in the range from 86 to 300 K are investigated for the (100) plane in the energy range from 8×103 to 22×103 cm?1 for the first time. Comparison of these spectra with those for the (111) plane reveals an essential absorption anisotropy in unpolarized light. The anisotropy is manifested in a much stronger splitting of the lowest energy band for the (100) plane in comparison with that for the (111) plane. With decreasing temperature, the splitting becomes smaller. Possible mechanisms for the anisotropy revealed are proposed.  相似文献   

20.
Recording radio emission from extensive air showers (EASs) is considered now as a new promising method for detecting ultra-high energy (E 0 > 5 × 1016 eV) cosmic rays. The results of calculation of EAS radio emission at frequencies from 40 to 80 MHz in the EAS energy range E 0 = 1014–1017 eV are reported here, and the possibilities of determining EAS parameters from the radio emission lateral distribution are discussed.  相似文献   

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