共查询到20条相似文献,搜索用时 156 毫秒
1.
S. Sounda A. Dhara M. Purkait C. R. Mandal 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):257-263
Post form of “boundary corrected continuum intermediate state (BCIS)”
approximation has been employed to study charge transfer cross-sections in collision of Cq+, Nq+ and Oq+ (q=1–5) with ground state atomic hydrogen in the energy range of 50–200 keV/amu. In this formalism we have adopted model
potential for the interaction of the active electron with the projectile ion. Calculated results for total charge transfer
cross-sections have significant improvement over other existing theoretical results in their comparison to the available experimental
findings except for singly charge ions. Sub-shell distribution for total charge transfer cross-section has also been reported
in graphical form. Predictions
suggested by Olson in connection with the sub-shell distribution of total charge transfer cross-section has been reaffirmed.
However, an oscillatory structure of charge state dependence of the total charge transfer cross-sections has not been found
in the present investigation. 相似文献
2.
We have measured fragmentation cross-sections of Ar projectile nuclei at beam energy of 400 A MeV using experimental set-ups with plastic nuclear track detectors and different targets. In this paper total charge changing cross-sections and elemental fragmentation cross-sections for the production of fragments with charges ZF > or = 7 in interactions with H, C, Al, Cu, Ag and Pb target nuclei are presented. The dependence of the cross-sections on the fragment charge number and target charge number are discussed. The experimental results are compared to predictions of semi empirical cross-section models. 相似文献
3.
N. Amin S. Mahmood M. Saleem M. A. Kalyar M. A. Baig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):331-337
The photoionization cross-sections from the 2p2P1/2, 3/2, 3d2D3/2, 5/2 and 3s2S1/2 excited states of lithium have
been measured at different ionizing laser wavelengths, above the first
ionization threshold. The experiments are performed by using a thermionic
diode working in the space charge limited mode and the cross-sections are
measured by employing the saturation technique. By changing the ionization
photon energy, a smooth frequency dependence of the cross-sections has been
observed for the 2p and 3d states. The cross-section from the 3s excited
state has been measured at a single photon energy. The measured values of
the photoionization cross are compared with the available data. 相似文献
4.
In the present study, CR39 track etch detector was calibrated with a new system and the total charge changing cross-section of 300 A MeV Fe26+ ion beam in aluminum target was measured. The CR39 nuclear track detectors were used to identify the incident charged particles and their fragments using an optical microscope DM6000 M and automated image analyzer system installed with Leica QWin Plus software. The CR39 detectors before and after the target were calibrated and found to have the same charge response; the charge resolution in both of the detectors were 0.19e and 0.20e, respectively. The calibration points were fitted with a polynomial of degree one and all the points are within the limits of the experimental errors. The response functions were also obtained and fitted with a polynomial of degree three which are quite good throughout Z/β = 4.6 to 41.4. The value of the total charge changing cross-section is σtot = (1663 ± 236) mb. The total charge changing cross-section was compared with the experimental results of others and also fitted by the Bradt-Peters geometrical cross-section. 相似文献
5.
John H. Heinbockel John W. Wilson Steve R. Blattnig Garry D. Qualls Francis F. Badavi Francis A. Cucinotta 《Radiation measurements》2006,41(9-10):1103-1114
It has long been recognized that galactic cosmic rays are of such high energy that they tend to pass through available shielding materials resulting in exposure of astronauts and equipment within space vehicles and habitats. Any protection provided by shielding materials result not so much from stopping such particles but by changing their physical character in interaction with shielding material nuclei forming, hopefully, less dangerous species. Clearly, the fidelity of the nuclear cross-sections is essential to correct specification of shield design and sensitivity to cross-section error is important in guiding experimental validation of cross-section models and database. We examine the Boltzmann transport equation which is used to calculate dose equivalent during solar minimum, with units (cSv/yr), associated with various depths of shielding materials. The dose equivalent is a weighted sum of contributions from neutrons, protons, light ions, medium ions and heavy ions using the ICRP-60 LET dependent quality factors. We investigate the sensitivity of dose equivalent calculations due to errors in nuclear fragmentation cross-sections. We do this error analysis for all possible projectile-fragment combinations (14,365 such combinations) to estimate the sensitivity of the shielding calculations to errors in the nuclear fragmentation cross-sections. Numerical differentiation with respect to the cross-sections will be evaluated in a broad class of materials including polyethylene, aluminum and copper. We will identify the most important cross-sections to ensure adequate experimental study and evaluate their impact on propagated errors in shielding estimates. 相似文献
6.
J.B. QiC.Y. Chen Y.S. Wang X.J. Xu 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,72(4):495-502
In this work, based on the calculation in detail, two new fitting formulae of total excitation and excitation autoionization cross-sections for Na-like ions (18?Z?39) are given. For discussing the variation of the total excitation autoionization cross-section, a systematic study of the dependence of the overall branching ratio on incident electron energy and nuclear charge is also carried out. 相似文献
7.
《中国物理C(英文版)》2021,45(6):062001-062001-14
The Back-n white neutron source(known as Back-n) is based on back-streaming neutrons from the spallation target at the China Spallation Neutron Source(CSNS).With its excellent beam properties,e.g.,a neutron flux of approximately 1.8×10~7 n/cm~2/s at 55 m from the spallation target,energy range spanning from 0.5 eV to 200 MeV,and time-of-flight resolution of a few per thousand,along with the equipped physical spectrometers,Back-n is considered to be among the best facilities in the world for carrying out nuclear data measurements.Since its completion and commencement of operation in May 2018,five types of cross-section measurements concerning neutron capture cross-sections,fission cross-sections,total cross-sections,light charged particle emissions,in-beam gamma spectra,and more than forty nuclides have been measured.This article presents an overview of the experimental setup and result analysis on the neutron-induced cross-section measurements and gamma spectroscopy at Back-n in the initial years. 相似文献
8.
In this paper we report our calculations on several important total cross-sections (TCSs) of positron impact on isoelectronic
N2 and CO molecules, treated in the complex spherical potential formalism. Basically the total (complete) cross-section Q
T consists of elastic and inelastic contributions. Our total inelastic cross-section (Q
inel) contains ionization and electronic excitations together with positronium formation. Our goal here is to bifurcate Q
inel further to deduce total ionization cross-section, using the ‘complex scattering potential–ionization contribution’ (CSP-ic)
method of electron–atom/molecule scattering. The present range of positron energy is 15–2000 eV. All the resulting cross-sections
are in a good general accord with the existing data. This work highlights the importance of various scattering channels in
e + -N2 and e + -CO interactions at intermediate and high energies. 相似文献
9.
10.
D. Zhou E. Semones S. Guetersloh N. Zapp M. Weyland E.R. Benton 《Radiation measurements》2010,45(8):916-922
Human will be sooner or later return to the moon and will eventually travel to the planets near Earth. Space radiation hazards are an important concern for human space flight in deep space where galactic cosmic rays (GCR) and solar energetic particles are dominated and radiation is much stronger than that in LEO (Low Earth Orbit) because in deep space there is no magnetosphere to screen charged particle and no big planet nearby to shadow the spacecraft.Research indicates that the impact of particle radiation on humans depends strongly on the particles' linear energy transfer (LET) and the radiation risk is dominated by high LET radiation. Therefore, radiation research on high LET should be emphasized and conducted systematically so as to make radiation risk as low as reasonably achievable (ALARA) for astronauts.Radiation around the moon can be measured with silicon detectors and/or CR-39 plastic nuclear track detectors (PNTDs). At present stage the silicon detectors are one of the preferred active dosimeters which are sensitive to all LET and CR-39 detectors are the preferred passive dosimeters which are sensitive to high LET (≥5 keV/μm water). CR-39 PNTDs can be used as personal dosimeters for astronauts. Both the LET spectrum and the charge spectrum for charged particles in space can be measured with silicon detectors and CR-39 detectors.Calibrations for a detector system combined with the silicon detectors CRaTER (Cosmic Rays Telescope for the Effects of Radiation) from Boston University and Massachusetts Institute of Technology, and the CR-39 PNTDs from JSC (Johnson Space Center) – SRAG (Space Radiation Analysis Group) were conducted by exposing the detector system to the accelerator generated protons and heavy ions. US space mission for the radiation measurement around the moon using CRaTER was carried out in 2009.Results obtained from the calibration exposures indicate an excellent agreement between LET spectrum and charge spectrum measured with CR-39 detectors and simulated with PHITS (Particle and Heavy Ion Transport System).This paper introduces the LET spectrum method and charge spectrum method using CR-39 PNTDs and the Monte Carlo simulation method for CR-39 detectors, presents and compares the results measured with CR-39 PNTDs and simulated for CR-39 detectors exposed to heavy irons (600 MeV/n) in BNL (Brookhaven National Laboratory) in front and behind the CRaTER. 相似文献
11.
N. Amin S. Mahmood M. Anwar-ul-Haq M. Riaz M. A. Baig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(1):23-28
The photoionization cross-section and number density of the 3p 2P1/2,3/2 excited levels of sodium have been measured as a function of the laser energy using two-step laser excitation in conjunction
with a thermionic diode working in the space charge limited mode. Employing
the saturation technique, the cross-sections for the 3p 2P1/2 and
3p 2P3/2 levels are determined as 2.16 (43) Mb and 3.74 (74) Mb respectively. 相似文献
12.
T. Renk 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):251-255
Following a prior analysis of measured pp elastic differential cross-sections, the impact parameter representation in terms of profile functions is calculated from
two different parametrizations of single diffractive dissociation data. The derivative of this quantity, with respect to the
collision energy squared s, measures the growth rate of the reaction's blackness. Its distribution in impact parameter space allows detailed insight
into the growth pattern of the total diffractive cross-section and the approaching unitarity limit. Comparing the results
with the elastic case, the different mechanisms of unitarization of two parametrizations are discussed.
Received: 19 January 2001 / Accepted: 11 July 2001 相似文献
13.
Weiwei Zhou Lorna Wilkinson Jason W. L. Lee David Heathcote 《Molecular physics》2019,117(21):3066-3075
ABSTRACTWe describe a newly upgraded instrument for measuring absolute total electron ionization cross-sections over the energy range from 0 to 300?eV, and present cross-sections for nine previously unstudied molecules, as well as several small molecules for which comparison data is available. The measured cross-sections are compared with the predictions of the BEB model, and show reasonable agreement with the model, albeit peaking at higher electron energies than predicted by the model. We show that the maxima in the cross-sections follow an additivity model, such that the molecular cross-sections can be expressed as a sum over contributions from the constituent atoms. These contributions have been determined from a global fit to the data for all molecules studied, and allow maximum cross-sections to be predicted for molecules that have not been studied to date. We demonstrate the expected correlation between the maximum ionization cross-section and the molecular polarisability, and show that the atomic contributions to the cross-section show a similar dependence on the atomic polarisability. The observed correlation can be used as an alternative method for predicting unknown maximum cross-sections. 相似文献
14.
15.
Tapan Mukhopadhyay D. N. Basu 《The European Physical Journal A - Hadrons and Nuclei》2010,45(1):121-124
Photonuclear reactions at energies covering the giant dipole resonance (GDR) region are analyzed with an approach based on
nuclear photoabsorption followed by the process of competition between light-particle evaporation and fission for the excited
nucleus. The photoabsorption cross-section at energies covering the GDR region is contributed by both the Lorentz-type GDR
cross-section and the quasi-deuteron cross-section. The evaporation-fission process of the compound nucleus is simulated in
a Monte Carlo framework. Photofission reaction cross-sections are analyzed in a systematic manner in the energy range of ∼
10-20 MeV for the actinides 232Th , 238U and 237Np . Photonuclear cross-sections for the medium-mass nuclei 63Cu and 64Zn , for which there are no fission events, are also presented. The study reproduces satisfactorily the available experimental
data of photofission cross-sections at GDR energy region and the increasing trend of nuclear fissility with the fissility
parameter Z
2/A for the actinides. 相似文献
16.
Ren Zhao Yue-Qin Wu Li-Chun Zhang 《International Journal of Theoretical Physics》2009,48(5):1231-1238
Using Damour-Ruffini method, Hawking radiation of rotating black strings is studied. Under the condition that the total energy,
total angular momentum and total charge are conservative, the transition probability from initial state (energy M+ω, charge Q+e and angular momentum J+m) to final state (energy M, charge Q and angular momentum J) for black strings is derived considering the reaction of radiation particles to spacetime. That is, the probability that
black strings radiate particles with energy ω, charge e and angular momentum m is obtained. The real spectrum is not a strictly pure thermal spectrum. Our result is consistent with Parikh and Wilczek’s
result. It satisfies the unitary principle of quantum mechanics. However, in our result there are not only the term that denotes
effect of energy and charge of radiation particles but also the term that denotes effect of radiation particles angular momentum
on rotating black strings angular momentum. We provide a new way for investigating radiation of black strings. 相似文献
17.
The real and imaginary parts,f’(E) and”(E) of the dispersion corrections to the forward Rayleigh scattering amplitude (also called anomalous scattering factors) for
the elements La, Ce, Pr, Nd, Sm, Gd, Dy, Ho and Er, have been determined by a numerical evaluation of the dispersion integral
that relates them through the optical theorem to the photoeffect cross-sections. The photoeffect cross-sections are derived
from the total attenuation cross-section data set experimentally determined using high resolution high purity germanium detector
in a narrow beam good geometry set-up for these elements in the photon energy range 5 to 1332 keV and reported earlier by
the authors. Below 5 keV, Scofield’s photoeffect cross-sections compiled in XCOM program have been interpolated and used.
Simple formulae forf” in terms of atomic number and energy have also been obtained. The data cover the energy region from 6 to 85 keV and atomic
numberZ from 57–68. The results obtained are found to agree fairly well with the other available data. 相似文献
18.
MJ Singh DO Kataria N Madhavan P Sugathan JJ Das DK Awasthi AK Sinha R Shanker 《Pramana》1999,53(4):743-764
A projectile ion-recoil ion coincidence technique has been employed to study the multiple ionization and the charge transfer
processes in collisions of 60–120 MeV Si
q+ (q = 4−14) ions with neutral argon atoms. The relative contribution of different ionization channels, namely; direct ionization,
electron capture and electron loss leading to the production of slow moving multiply charged argon recoil ions have been investigated.
The data reported on the present collision system result from a direct measurement in the considered impact energy for the
first time. The total ionization cross-sections for the recoil ions are shown to scale as q
1.7/E
p
0.5
, where E
p is the energy in MeV of the projectile and q its charge state. The recoil fractions for the cases of total- and direct ionizations are found to decrease with increasing
recoil charge state j. The total ionization fractions of the recoils are seen to depend on q and to show the presence of a ‘shell-effect’ of the target. Further, the fractions are found to vary as 1/j
2 upto j = 8+. The average recoil charge state 〈j〉 increases slowly with q and with the number of lost or captured electrons from or into the projectile respectively. The projectile charge changing
cross-sections σ
qq′ are found to decrease with increasing q for loss ionization and to increase with q for direct-and capture ionization processes respectively. The physics behind various scaling rules that are found to follow
our data for different ionization processes is reviewed and discussed. 相似文献
19.
In the present work, the total cross-sections for single- and
double-electron-capture by low-energy highly-charged Neq+ (q =2-6)
recoil ions from He atomic gas have been measured in the energy range
600–1000 eV/q. These measurements are compared with other available
experimental results. The charge state dependence of the
single-electron-capture cross-sections for Neq+ (q = 2-6) recoil ions
incident on He at energy of 1000 eV/q is compared with the theoretical
predictions of the absorbing sphere model and the classical model. 相似文献
20.
R. Anni 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):361-374
A simple recipe for revealing classical-like properties of optical-potential cross-sections is proposed. The recipe is based
on the fact that the classical properties are not expected to depend on the actual value of . This allows us to identify
the classical-like characteristics of an optical-potential cross-section by simply repeating the calculation with different
values of , and observing which properties of the cross-section are invariant. The method is applied to the cross-sections
of a few optical potentials used to describe the recent data of light heavy-ion elastic scattering. An improved near-side/far-side
decomposition is used to separate the near-side and far-side components of the optical-potential cross-sections.
Received: 4 September 2001 / Accepted: 3 June 2002 / Published online: 26 November 2002
RID="a"
ID="a"e-mail: anni@le.infn.it
Communicated by V. Vento 相似文献