共查询到20条相似文献,搜索用时 687 毫秒
1.
In this paper, we report a new method to determine the effective atomic number, Z
eff, of composite materials for Compton effect in the γ-ray region 280–1115 keV based on the theoretically obtained Klein–Nishina scattering cross-sections in the angular range
50°–100° as well as a method to experimentally measure differential incoherent (Compton) scattering cross-sections in this
angular range. The method was employed to evaluate Z
eff for different inorganic compounds containing elements in the range Z = 1–56, at three scattering angles 60°, 80° and 100° at three incident gamma energies 279.1 keV, 661.6 keV and 1115.5 keV
and we have verified this method to be an appropriate method. Interestingly, the Z
eff values so obtained for the inorganic compounds were found to be equal to the total number of electrons present in the sample
as given by the atomic number of the elements constituting the sample in accordance with the chemical formula of the sample.
This was the case at all the three energies. 相似文献
2.
A recently reported study [Phys. Rev.
A49, 3664 (1994)] of elastic scattering of 81 keVγ rays in the angular range from 60° to 133° has been extended to smaller and larger angles. Previously reportedS matrix calculations of atomic Rayleigh scattering have been shown to require a subtraction of contributions from spurious
resonances. Most of the experimental data are in agreement with the calculations. Calculations (MF + ASF) based on a combination
of relativistic modified form factors (MF’s) and angle independent anomalous scattering factors (ASF’s) are found to be inadequate
for an explanation of experimental cross-sections in the case of highZ elements at angles larger than about 120°. 相似文献
3.
《Journal of Electron Spectroscopy and Related Phenomena》2005,142(1):39-43
With the help of a Ge(Li) detector, the incoherent scattering differential cross-sections by 59.54 keV γ-rays from the 10 elements in the atomic region 23 ≤ Z ≤ 51 were measured through angles from 30° to 140°. The background correction and detection efficiency are also included in this study. The present results constitute the first measurements for this combination of energy and angle. The present experimental results have been compared with those estimated on the basis of the nonrelativistic Hartree-Fock wave functions. The present results were in good agreement with those of [J.H. Hubbell, W.J. Veigele, E.A. Briggs, R.T. Brown, D.T. Cromer, R.J. Howerton, J. Phys. Chem. Ref. Data 4 (1975) 471]. 相似文献
4.
A. N. Khopersky A. M. Nadolinsky K. Kh. Ikoeva O. A. Khoroshavina 《Optics and Spectroscopy》2012,112(1):44-49
Using the Zn atom as an example, beyond the scopes of the impulse approximation and the incoherent scattering-function approximation,
we study the absolute value and the shape of the double differential nonresonance Compton scattering cross section of an X-ray
photon by an atom with the core of the d symmetry. We take into account the effects of radial relaxation of shells in the field of core vacancies and of elastic (Thomson
and Rayleigh) scattering. Calculation results have a predictive character and, for the incident photon energies of 14.93 and
22.10 keV and the scattering angles of 141° and 133°, agree well with experimentally determined values of the differential
Compton scattering cross section. 相似文献
5.
C. Jara-Figueroa A. B. Klimov L. Roa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(3):1-6
In this paper, we report the coherent scattering cross sections of some lanthanides at low momentum transfer in four angular ranges of (0°?4°), (0°?6°), (0°?8°) and for 241Am (59.54 keV) and 137Cs (661.6 keV) gamma rays. The coherent scattering cross sections were derived by subtracting the small contribution of the corresponding angle integrated incoherent scattering cross sections from the experimentally measured total (coherent + incoherent) scattering cross sections for the elements and energies of interest. The coherent scattering cross sections were found to agree with the corresponding theoretical cross sections within the range of experimental errors. The theoretical coherent scattering cross sections were computed by numerically integrating the S-matrix data of the elements in the angular ranges of interest. The incoherent scattering cross sections were based on the compilations which make use of the non-relativistic Hartree-Fock (NRHF) model for the atomic charge distribution. 相似文献
6.
A Raghava Rao SS Ramana Reddy K Premchand K L Narasimham K Parthasaradhi V Lakshminarayana 《Pramana》1982,18(3):271-278
The values of incoherent scattering functions are determined experimentally for 145 keV gamma rays in elements Au, Ag and
Y at scattering angles 40°, 70° and 100°, using a x-ray gamma coincidence technique. The corresponding theoretical values
are obtained from the tabulations of Hubbellet al, and computed from the models of Jauch and Rohrlich and Shimizuet al. A comparison between the theoretical and experimental results showed that the non-relativistic approach adopted in the theory
of Shimizuet al is inapplicable to the present cases. A gross agreement is noticed between the present experimental results and the other
theoretical values. 相似文献
7.
M. Ismail A. Farraga H. A. Abdusalam Th. El-Sherbini 《International Journal of Theoretical Physics》2004,43(1):111-125
The scattering of electrons by atomic copper has been studied using Born approximation and the concept of the generalized oscillator strength (GOS). Differential and total cross-sections for the excitation of the 3d10 4p2 P state are calculated at incident energies of 100 eV and are compared with other available experimental and theoretical data. The agreement between our calculation for the differential cross-section and the available experimental results is fairly good at the forward angles, while the agreement at large angles is poor. The calculated total cross-sections are compared with the experimental data and those predicted by several theories. It is found that our calculation for the total cross-sections are in a good agreement with the close coupling calculation of Msezane and Henry (1986a, Physical Review A
33, 1631) for incident energies greater than 20 eV. The integrated cross-section measurements of Ismail and Teubner (1995, Journal of Physics B: Atomic, Molecular and Optical Physics
28, 4164) are in good agreement with the present calculation. 相似文献
8.
The absolute doubly differential cross-sections (DDCS) for production of the thick-target X-ray bremsstrahlung spectra in
collisions of 6.5 keV and 7.5 keV electrons with thick Hf target are measured. The X-ray photons are counted by a Si(Li) detector
placed at 90° to the electron beam direction. The bremsstrahlung spectra are corrected for various ‘solid-state effects’ namely,
electron energy-loss, electron back-scattering, and photon-attenuation in the target, in addition to the correction for detector’s
efficiency. The DDCS values after correction, are compared with the predictions of a most accurate thin-target bremsstrahlung
theory [H K Tseng and R H Pratt,Phys. Rev.
A3, 100 (1971); Kisselet al, Atomic Data Nucl. Data Tables
28, 381 (1983)]. Also, a dependence of the absolute DDCS on atomic numberZ of the targets (47Ag,79Au and72Hf) at 7.0 keV and 7.5 keV electron energies has been studied. The agreement between experiment and theory is found to be
satisfactory within 27% systematic error of measurements. However, an apparent systematic difference between experiment and
theory in the region of low-energy photons has been explained qualitatively by considering the fact that the hexagonal atomic
structure of Hf offers possibly a greater magnitude of ‘solid-state effects’ in respect of blocking the low-energy bremsstrahlung
photons from coming out of the target surface than does the cubic-face centered structure of Ag and Au target in similar conditions
of the experiment. 相似文献
9.
G. Apaydın E. Tıraşoğlu Ö. Söğüt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):487-492
The M X-ray production differential cross sections in Re, Bi and U elements
have been measured at the 5.96 keV incident photon energy in an angular
range 135°–155°. The measurements were performed using a 55Fe
source and a Si(Li) detector. The present results contradict the predictions
of Cooper and Zare [Atomic Collision Processes, Gordon and Breach, New York (1969)]
and experimental results of Kumar et al. [J. Phys. B: At. Mol. Opt. 34,
613 (2001)]. that, after photoionization of inner shells, the vacancy state has equal
population of magnetic substates and the subsequent X-ray emission is
isotropic, but confirm the predictions of the calculations of Flügge et
al. [Phys. Rev. Lett. 29, 7 (1972)] and experimental results of Sharma and Allawadhi [J. Phys. B: At. Mol. Opt. 32, 2343 (1999)] and Ertugrul [Nucl. Instrum. Meth. B 119, 345 (1996)].
Total M X-ray production cross sections from the decay at the 5.96 keV
photon energies are found to be in good agreement with the calculated
theoretical results using the theoretical values of M shell photoionization
cross section. 相似文献
10.
Based on new experimental investigations of elastic p
6Li scattering at energies 500–1150 keV and angles 30–170°, a phase analysis is performed and interaction potentials for p
6Li-system in 2,4S- and 2P-states are constructed. 相似文献
11.
Interaction of positrons with atoms and molecules differs from electron
interaction due to the difference in polarity of the charge. This makes
positrons an alternative tool to study atomic and molecular structure.
Recent measurements of the total cross-sections for positron scattering at
low energies on He, Ar, H2, N2, C6H6, C6H12,
C6H7N carried out at Trento University [Karwasz et al., Acta Phys.
Pol. 127, 666 (2005)] are discussed and compared to electron scattering
results. All measured total cross-sections exhibit an increase with
decreasing positron energy in the limit of zero energy; H2, N2,
Ar, show regions of constant cross-section which are a few eV-wide,
characteristic of scattering on a hard-sphere potential. Helium shows two
resonant structures much below the positronium formation threshold. They may
be attributed to virtual positronium formation. In conclusion, positron
scattering is complementary to electron scattering. The total cross-sections
do not show Ramsuaer minima but constant values, and new resonances appear. 相似文献
12.
Double differential cross sections for total δ-electron and K shell δ-electron emission in two angles 45° and 135° and energies 200 eV–7 keV are measured with 6 MeV p on Ar. The cross sections for K shell δ-electron emission are compared with recent calculations in PWBA with an OPM effective atomic potential5 and in SCA with an effective charge Coulomb potential12. 相似文献
13.
F. Schümann S. Zavatarelli L. Gialanella U. Greife M. Junker D. Rogalla C. Rolfs F. Strieder H.P. Trautvetter 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):337-342
Abstact: The elastic scattering cross sections, σ (E,θ), for the systems He+Ta and He+W have been measured at θlab=165° and E
lab=76.1 keV to 3.988 MeV using targets with a thickness of a few atomic layers. The results are smaller than the results given
by the Rutherford scattering law, σR(E,θ), due to the effects of electron screening and can be described by σ(E,θ)/σR(E,θ)=(1+Ue/E)−1, where U
e is an atomic screening potential energy. The deduced average value, U
e=28 ± 3 keV, is consistent with the Moliére- and Lenz-Jensen-models as well as electron binding energies.
Received: 25 May 1998 相似文献
14.
A. R. Milosavljević F. Blanco D. Šević G. García B. P. Marinković 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):107-114
Differential cross-sections (DCSs) for elastic
scattering of electrons from tetrahydrofurfuryl alcohol (THFA),
which can be considered as an analogue molecule to DNA sugar
deoxyribose, were determined using crossed beam measurements for
incident energies from 40 eV to 300 eV and scattering angles from
30° to 110°. The relative DCSs were measured both as a
function of incident electron energy and scattering angle,
allowing absolute calibration of the whole data set via
normalization to a single point. The absolute calibration has been
performed according to calculated absolute DCSs obtained by the
corrected independent atom method using an improved quasifree
absorption model. The calculated data-set includes DCSs and
integral elastic and inelastic cross-sections in the incident
energy range from 5 eV to 5000 eV. The theoretical results agree
very well with the experimental ones, regarding the shape of DCSs.
Moreover, the same theoretical procedure has been used to obtain
DCSs for elastic electron scattering from a simpler deoxyribose
analogue tetrahydrofuran (THF), which agree very well, both in
shape and on the absolute scale, with the recent experimentally
obtained absolute DCSs [A.R. Milosavljević et al., Eur. Phys.
J. D 35, 411 (2005)]. The present results are also
compared with the recent theoretical data for THF and THFA.
Finally, according to both experimental and theoretical data, the
DCSs for elastic electron scattering from THFA and THF molecules
appear to be very similar both in shape and absolute scale. 相似文献
15.
Total attenuation cross sections of copper and silver have been measured in the energy range 5 to 85 keV in a narrow beam
good geometry set up using X- andγ-rays emitted from radio isotopes, by employing a high resolution hyper pure germanium detector. From the measured values,
the photoeffect cross-sections have been derived by subtracting a small contribution of the sum of the theoretical coherent
and incoherent scattering cross sections. The photoeffect cross-sections so obtained are found to be in better agreement with
the unrenormalized values of Scofield [10]. These photoeffect cross-sections have been used to evaluate the dispersion corrections
(also called anomalous scattering factors)f
+ andf″ for the forward Rayleigh scattering amplitude by a numerical evaluation of the dispersion integral that relates them at the
energies at which the cross-sections have been measured. To thef
+ values so obtained, the relativistic corrections proposed by different investigators are included separately and the valuesf′ so obtained are compared with the available data and discussed. Possible conclusions are drawn from the present study. 相似文献
16.
G K Raju K Venkataramaniah M S Prasad K Narasimhamurty V A Narasimhamurty 《Pramana》1986,26(4):327-335
Differential incoherent scattering cross-section ratios of 279.2 keV photons by zirconium, tin, tantalum, lead and uranium
elements are experimentally determined by comparing the peak areas under the degraded photon energy with that of an equivalent
aluminium foil employing a high resolution 35 c.c. coaxial Ge(Li) detector. Studies have been made in single configuration
in an angular range of 20° to 115°. The results are compared with theoretical values obtained from the non-relativistichfs model of Hubbell and co-workers. The cross-section ratios decrease as the atomic number increases for a given scattering
angle. 相似文献
17.
S. B. Dubovichenko 《Russian Physics Journal》2008,51(11):1136-1143
Based on experimental research of elastic р
12С scattering for energies of 200–1110 keV (in the center-of-mass system) and angles of 10–170°, the phase analysis of the
р
12С system in the S-state is performed and the interaction potential is constructed.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 21–27, November, 2008. 相似文献
18.
Absolute differential cross-sections ofp+12C elastic scattering have been measured atθ cm=89.1°, 118.7°, 146.9° for bombarding energies between 0.3 and 2.0 MeV. Revised level parameters of the first three excited states in13N have been extracted with aR-matrix analysis. It is shown that the influence of the bound ground-state of13N has an appreciable effect on low-energy scattering. Recent predictions concerning Mott-Schwinger polarization are also discussed. 相似文献
19.
The differential cross sections for elastic scattering of 662 keV and 279 keV γ-rays from Pb, Ta, Nd, Sn, Mo, and Zn have been measured at angles ranging from 45° to 135°. The results are compared with theoretical predictions taking into account Rayleigh scattering and nuclear Thomson scattering. The theoretical Rayleigh amplitudes are based on second order perturbation theory according to Brown et al. and on form factors calculated from relativistic HFS wave functions. A semi-empirical method of correcting the form factors is developed, valid for energies between 150 keV and 750 keV and charge numbers up to Z = 82. The average difference between calculated and measured differential cross sections was found to be 6%. 相似文献
20.
Yu. A. Fainberg Ya. A. Teplova N. V. Novikov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(3):494-497
The energy and charge distributions of protons and hydrogen atoms reflected from the Cu surface in the case of grazing incidence
angles are measured at energies of incident particles (H+ and H0) of 200 and 250 keV. The charged fractions of reflected particles are analyzed. A weak dependence of the neutral fraction
of reflected particles on the scattering angle is discovered for incidence angles of 1°–2° and an energy of scattered particles
of 60 keV or less. It is shown that the neutral fraction of reflected particles with an energy of 60–80 keV or more is independent
of the scattering angle and is determined by the ratio of the cross sections for the electron capture and loss by ions in
the material. 相似文献