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1.
Nuclear resonance scattering of photons from 15N has been used to study the orientation of the HNO 3 intercalant molecule with respect to the graphite planes. In the second-stage compound C 10(HNO 3) and the temperature range T = 15°K ? 300°, no orientational phase transition was observed and the NO 3 molecular plane was found to be oriented at an angle θ ∽ 82 ± 8° with respect to the graphite planes. 相似文献
2.
The isothermal compressibilities of pristine graphite and stages 1 and 2 potassium-graphite have been measured at room temperature. Diamond anvil X-ray diffraction techniques were employed to determine the c-axis lattice constant as a function of hydrostatic pressure up to 12 kbar. The compressibilities were found to be (2.73±0.09)×10 -12, (2.13±0.09)×10 -12, (5.3±0.8)×10 -12 and for graphite, KC 8, stage 2 KC 24 and stage 3 KC 24, respectively. The compressibility of KC 8 was comparable to that of RbC 8 deduced from neutron scattering experiments. 相似文献
3.
The binding energy of the C 1s-level of clean pyrolytic graphite and amorphous carbon has been measured by means of the excitation-curve
technique. Values of E
C 1s
B
=284.31±0.2 eV for graphite and amorphous carbon have been found. 相似文献
4.
It is shown that during low-temperature (300–500 K) intercalation of sodium atoms into thin multilayer graphene and graphite films on rhenium the first graphene layer plays the role of a trap to which atoms coming on the surface diffuse through a graphite film. The intercalation phase of the interlayer space in the graphite bulk is actively filled at a sodium atoms concentration under the first graphene layer close to the maximum possible (2 ± 0.5) × 1014 cm–2. This phase capacity is proportional to the graphite film thickness that can be varied in this work from one graphene layer to ~50 atomic layers. The diffusion energy E
d
of Na atoms through the graphite film was estimated to be E
d
≈ 1.4 eV. 相似文献
5.
Superconductivity was observed in the graphite intercalation compounds, KHgC 8 and RbHgC 8, using an AC induction technique. The transition temperatures were 1.90K and 1.44K for KHgC 8 and RbHgC 8 respectively. A full Meissner effect was observed for KHgC 8 with a temperature dependant anisotropy in critical field with a value of 25 ± 5 at T c. 相似文献
6.
The El character of the de-excitation of the 9 to 10 MeV states in 40Ar has been studied through the reaction 36S(α, γ) 40Ar. Angular distributions and γ-yield asymmetries of primary transitions from the Eα = 2.35 to 3.50 MeV resonances have been measured. The Doppler-shift attenuation method was used to obtain the following lifetime values: 720 ± 120 fs ( Ex= 2.52 MeV), 89 ±17 (3.21), 90±17(3.511), 22 ±9 (4.33), and 105 ± 17 (4.60). 相似文献
7.
In order to investigate fractionation of calcium (Ca) isotopes in vertebrates as a diagnostic tool to detect Ca metabolism dysfunction we analyzed the Ca isotopic composition (δ 44/40Ca?=?[( 44Ca/ 40Ca) sample/( 44Ca/ 40Ca) reference]?1) of diet, faeces, blood, bones and urine from Göttingen minipigs, an animal model for human physiology. Samples of three groups were investigated: 1. control group (Con), 2. group with glucocorticosteroid induced osteoporosis (GIO) and 3. group with Ca and vitamin D deficiency induced osteomalacia (?CaD). In contrast to Con and GIO whose average δ 44/40Ca faeces values (0.39?±?0.13‰ and 0.28?±?0.08‰, respectively) tend to be lower than their diet (0.47?±?0.02‰), δ 44/40Ca faeces of ?CaD (?0.27?±?0.21‰) was significantly lower than their δ 44/40Ca diet (0.37?±?0.03‰), but also lower than δ 44/40Ca faeces of Con and GIO. We suggest that the low δ 44/40Ca faeces of ?CaD might be due to the contribution of isotopically light Ca from gastrointestinal fluids during gut passage. Assuming that this endogenous Ca source is a common physiologic feature, a fractionation during Ca absorption is also required for explaining δ 44/40Ca faeces of Con and GIO. The δ 44/40Ca urine of all groups are high (>2.0‰) reflecting preferential renal reabsorption of light Ca isotopes. In Göttingen minipigs we found a Ca isotope fractionation between blood and bones (Δ 44/40Ca blood-bone) of 0.68?±?0.15‰. 相似文献
8.
A quadrupole moment of 37 ?8+14 b has been deduced for the 40 ps shape isomer in 236Pu. The value has been derived from a measured delayed fission fragment angular distribution with an anisotropy of 1.48 ± 0.15 for the isomeric decays at 30°. The deformation of the second minimum expressed by the axes ratio of a spheroid is found to be 2.0 ± 0.3. 相似文献
9.
The morphology and electronic structure of 13C-isotope-based graphite composites were studied by transmission electron microscopy (TEM), x-ray diffraction, and x-ray fluorescence spectroscopy. High-resolution TEM images showed that composites contain several forms of carbon particles. According to an x-ray diffraction analysis, the size of graphene stacks of graphite particles is 20 and 40 Å. The C K α x-ray fluorescence spectra of the initial 13C isotope powder and composites based on it detected an increase in the density of high-energy occupied states in comparison with the graphite spectrum. Ab initio quantum chemical calculation of the structure of C 150 graphene showed that the increase in the density of states stems from the electrons of dangling bonds of boundary carbon atoms of particles ~20 Å in size. Electrical properties of 13C-isotope-based samples were studied by analyzing the temperature dependence of the conductivity. It was assumed that the change in the logarithmic dependence of the conductivity observed at liquid-helium temperatures to the linear dependence as the temperature increases is caused by carrier transfers between the disordered graphene layers forming a nanocomposite. 相似文献
10.
The secondary emission of carbon atoms from the (0001) plane of graphite nanocrystallites bombarded with argon ions with energies of 1 and 10 keV and the incidence angle α = 45° is investigated. The unusual oscillating energy distributions of secondary C + ions with main maxima E max in the range of 40–60 eV and peaks corresponding to the energies E 1 ≈ 20, 30, 70, 80, and 100 eV have been revealed. The C + ion yield decreases, the energy spectrum increases, and the maximum E max shifts to larger energies E 1 with increasing emission angle (with respect to the normal to the surface). The secondary-ion emission from the (0001) face of graphite is numerically simulated with allowance for the charge exchange of secondary ions to obtain a qualitative explanation of the observed results. 相似文献
11.
The (n th, α) (n th, p) and (n th, γα) reactions spectroscopical data are reported on 40K and 143Nd. For 40K, values of σ α = 0.39 ± 0.08 b, σ p = 4.4 ± 0.9 b, σ γα = 26 ± 4 mb are obtained and accurate measurements of Eα0 = 3491.7 ± 7 keV and Epo = 2232.9 ± 3 keV have been performed, α1, and p 1 transitions and the 40K(n th, γp) reaction have not been observed. The 40K(n th, γα) 37Cl and 143Nd(n th, γα) 140Ce spectra are presented. The multipolarity of the primary low energy γ-rays is deduced from the γ-α spectra. 相似文献
12.
ABSTRACTThe sound velocity properties of single-crystal rhodochrosite (MnCO 3) were determined up to 9.7?GPa at ambient temperature by Brillouin scattering spectroscopy. Six elastic constants were calculated by a genetic algorithm method using the Christoffel's equations at each pressure. The elastic constants increased linearly as a function of pressure and its pressure derivatives ? Cij/? P for C 11, C 33, C 44, C 12, C 13, C 14 were 5.86 (±0.36), 3.82 (±0.44), 2.06 (±0.39), 5.07 (±0.27), 5.34 (±0.44), 1.52 (±0.24), respectively. Based on the derived elastic constants of rhodochrosite, the aggregate adiabatic bulk and shear moduli ( Ks and G) were calculated using the Voigt-Reuss-Hill averages and the linear fitting coefficients (? Ks/? P) T and (? G/? P) T were 5.05(±0.26) and 0.73(±0.05), respectively. The aggregate Vp of rhodochrosite increased clearly as a function of pressure and its pressure derivative ? Vp/? P was 7.99(±0.53)?×?10 ?2?km/(s?GPa), while the aggregate Vs increased slowly and ? Vs/? P was only 1.19(±0.12)?×?10 ?2?km/(s?GPa). The anisotropy factor for As of rhodochrosite increased from ~40% at 0.8?GPa to ~48% at 9.7?GPa, while Ap decreased from ~19% to ~16% at the corresponding pressure. 相似文献
13.
Auger spectra of thin fullerite (C 60) films have been measured under the conditions precluding their electrostatic charging and destruction. The Auger line of
these subjects, E
f=268.3±0.2 eV, turned out to lie considerably lower in energy than that of the ion-beam amorphized graphite ( E
AG=272.3±0.2 eV) and of pyrographite ( E
PG=271.8±0.5 eV). Fullerite was found to convert to a graphitic form under irradiation by low-intensity electron beams used
customarily in AES, reflection EELS, and inverse photoemission spectroscopy. It has been established that such beams produce
noticeable changes in the fullerite structure already in a few minutes of irradiation.
Fiz. Tverd. Tela (St. Petersburg) 39, 187–190 (January 1997) 相似文献
14.
The feasibility is studied of using the laser-pyrolysis technique for determination of the radiative lifetimes of molecules.Measurements of time-resolved spectral emission were made on spatially resolved sections of the luminous plume produced by laser illumination of a graphite target in a vacuum. The nature of certain emission continua was investigated. The effects on C 2 Swan band emission of focal spot size, illumination power density, height and width of the plasma section observed and its distance from the target were studied. Conditions were determined for measuring physically significant radiative lifetimes for the d3Πg, v=0 and v=1 levels, of C 2. In particular, the laser flux used was 3.8×10 8W- cm?2 while observations were made of a plume section from 0.5 to 0.7 mm from the target. The results, τ(0,0)=235±20 ns, τ(0,1)=250±20 ns, τ(1,0)=255±20 ns, are compared with those obtained by other methods. They are in good agreement with results obtained by pulsed electron excitation. Analysis of the experimental conditions in previous experiments using the laser-pyrolysis technique for measuring τ( d3Πg of C 2 shows that they could not have lead to meaningful results of purely molecular properties. 相似文献
16.
Studies of the natural γ-emitting radionuclides in different types of cements manufactured by different companies in Egypt ( e.g. Iron (HI), Karnak (HK), and Super fine (HSu) products from Helwan Ltd.) have been done to determine their natural levels of radioactivity using a high-purity germanium detector (HPGe). Knowledge of radioactivity present in cement materials enables one to assess any possible radiological risks to human health. The results show that the highest mean values of 226Ra and 232Th activity are 234.01±20.12 and 46.56±4.65 Bq kg ?1, respectively, measured in cement sample ‘Iron’ from Helwan company (HI). The corresponding value of 40K is 333.53±26.68 Bq kg ?1 measured in cement sample ‘Karnak’ from Helwan company (HK). For 137Cs, this value is 3.27±0.31 Bq kg ?1 measured in cement sample (HI). The average concentrations of measured radionuclides in the different cement samples are 72.21±6.39, 24.98±2.24, 134.49±10.45, and 0.58±0.08 Bq kg ?1 for 226Ra, 232Th, 40K, and 137Cs, respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries. Radium equivalent (Ra eq) activities and different hazard indices were calculated to assess the radiation hazard. Iron HI cement sample shows a higher Ra eq activity of 311.91±31.10 Bq kg ?1. Calculations of absorbed doses in nGy h ?1 show that the Iron (HI), Karnak (HK), and Super fine (HSu) products from Helwan company have higher activities than the permissible level (80 nGy h ?1). On the basis of the external hazard index ( H ex), Ra eq activities, and annual effective dose rates for organs ( H organ), the natural radioactivity of cement samples is not greater than the recommended values in the established standards and hence safe for use in building constructions and therefore for inhabitants. 相似文献
17.
The technique of time-differential perturbed angular correlations of γ-rays (TDPAC) has been applied to the study of graphite indium chloride using 111In as a probe. The results indicate the presence in the intercalated sample of two static quadrupole interactions with frequencies v (1)Q = 55.83±0.04 MHz and v (2)Q = 270.44±0.05 MHz, plus a time-dependent interaction with decay constant . The electric field gradient components for the static interactions were determined together with corresponding asymmetry and width parameters. 相似文献
18.
The alpha decay width and total width of the first 0 +, T = 2 state in 40Ca have been measured by the elastic scattering of α-particles from 36Ar. The results are Γα0 = 80 ± 10 eV and Γ = 81 ± 10 eV. 相似文献
19.
The microwave spectrum of 3,4-epoxy-1-butene has been studied in the region 26.5–40 GHz. For the ground-state molecule, 170 lines have been assigned up to J = 34. From these the rotational constants and the centrifugal distortion constants were determined by least-squares fitting. The rotational constants are (in MHz): A = 17367.284 ± 0.011, B = 3138.186 ± 0.004, C = 3043.697 ± 0.004. The dipole moment has been determined from the Stark effect as (in Debye): μa = 0.72 ± 0.01, μb = 1.688 ± 0.003, μc = 0.39 ± 0.02, μ = 1.875 ± 0.005. The rotational constants and dipole moment components indicate that the assigned conformer is the s-trans form. A rotational assignment has also been made for the first excited state of the torsional mode. The fundamental frequency of the torsional mode has been estimated as 142 ± 20 cm ?1 from relative intensity measurement. 相似文献
20.
The microwave spectra of methyl isocyanide and its 15N derivative in the 3 ν8 state have been observed from 40 to 180 GHz. After the assignment by a graphical method, the analysis has been carried out, first by the reuse of analytical formulas and then by the diagonalization of the energy matrix. Many accidental resonances have been shown to occur between the l = ±1 states, and A1A2 doublings for K, l = ±3, ±3 have been discovered. A set of constants in the 3 ν8 state is given for each molecule. 相似文献
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