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1.
Dr. Minakshi L. K. Jha S. N. Chatterjee B. N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):331-339
H+ and He2+ impact single and double ionization cross
sections of ground state lead atoms have been calculated in the binary
encounter approximation. Calculations of direct double ionization cross
sections have been performed in the modified double binary encounter model.
The accurate expressions of σΔE (cross-section for energy
transfer ΔE) and Hartree-Fock velocity distributions for the target
electrons have been used throughout the calculations. Contributions to
double ionization from Auger effect following ionization of inner shells
have been considered in the present work. Our H+ impact single and
double ionization cross sections are in good agreement with the experimental
observations. In calculations of He2+ impact cross sections, the
present theoretical approach shows limited success in the experimentally
investigated region (50–350 keV amu-1). 相似文献
2.
K-shell ionization cross section measurements are reported for35Br,37Rb and39Y targets caused by protons over 300–400 keV energy range in 20 keV increment. The K-shell ionization cross sections (σ
k
l
) at different energies were deduced from the Kα and Kβ X-ray production cross sections which were obtained from X-ray yields of the Kα and Kβ transitions. The experimental values are compared with the calculated values of ECPSSR theory and empirical reference cross
sections. The resultant K-shell ionization cross sections are found to be in reasonable agreement with the ECPSSR theory.
The Kα/Kβ intensity ratios are also presented and compared with other experimental values and also with the theoretical one-hole values
given by Scofield. 相似文献
3.
Electron impact single and double ionization cross sections of gallium have been calculated in the binary encounter approximation
using accurate expression for σΔ;E including exchange and interference as given by Vriens and Hartree-Fock velocity distributions for the target electrons throughout
the calculations. It is concluded that the ionization of 3d shell contributes partly to single ionization and partly to double
ionization. The results so obtained show reasonably good agreement with the experimental data. 相似文献
4.
The cross sections of the photoionization and the electron impact-induced ionization of Yb atoms from the excited 6s6p(3
P
1) state are numerically calculated. Matrix elements are computed in multielectron relativistic and nonrelativistic approximations
with allowance for the superposition of configurations and a relaxation effect. The radial part of the electron wavefunction
in a continuous spectrum is calculated using the solutions to one-configuration Hartree-Fock and Dirac-Fock equations. The
cross sections calculated by a relativistic method are compared to those for a nonrelativistic approximation. The ratios of
the radiation reduced matrix elements and the phase shifts of the wavefunctions of a continuous spectrum calculated for the
6p ɛs and 6p → ɛd transitions are compared to the values obtained by approximating the experimental dependences of the angular distribution
of photoelectrons for the photoionization by ultraviolet radiation from an oriented excited state. 相似文献
5.
H. Getahun L. F. Errea C. Illescas L. Méndez I. Rabadán 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(1):45-49
Single electron capture and single ionization total cross sections in collisions of proton with ethylene are calculated for
an
energy range 25 keV ≤
E
≤ 150 keV, using the classical trajectory Monte Carlo method. Multi-center model potentials are employed to represent
the interaction of the active electron on each molecular orbital with the C2H4+_{4}^{+} core. The results are compared with experimental results for single electron capture. 相似文献
6.
M. Vinodkumar K. Korot P. C. Vinodkumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):379-387
In this article, we report calculations of total
ionization cross sections, Q
ion
, for simple atoms (C, N, O, F) and
molecules (NO and NH3)_{3}) of atmospheric interest on electron impact at
energies from threshold to 2000 eV. We have employed the complex scattering
potential – ionization contribution (CSP-ic) method for the present study.
Attempt has been made to improve the method by computing the parameter that
involves the ratio of sum of the total excitation cross sections
(Σ
Q
exc
) and total inelastic cross section (Q
inel
) at the peak of the
inelastic cross section. The present study not only provided a better
estimation of the parameter involved in the CSP-ic method but also provided
better agreement with the available experimental and theoretical data on the
ionization cross sections of the simple atomic and molecular targets studied
here. 相似文献
7.
Using the configuration interaction Pauli-Fock including core polarization (CIPFCP)
approach we have calculated absolute total and partial cross sections for photoionization
of excited
mp
5(m + 1)p J = 0−3
levels in Ar, Kr and Xe (m = 3−5) near threshold. Particular emphasis is
paid to the lineshapes of the odd mp
1/25
n(s/d)′
autoionizing
resonances and their variation with the character of the intermediate excited
J = 0−3 state. For selected intermediate levels of Ar and Kr the
computed cross sections are compared with laser spectroscopic measurements; good agreement
between the theoretical and experimental lineshapes and branching ratios for different
resonances is observed. 相似文献
8.
The total cross sections for positron impact on hydrocarbons have been calculated using the additivity rule in which the total
cross section for a molecule is the sum of the total cross section for the constituent atoms. The energy range considered
is from a few eV to several thousand eV. The total cross sections for positron impact on an atom are calculated by employing
a complex spherical potential which comprises of a static, polarization and an absorption potential. We have good agreement
with the experimental results for hydrocarbons for positron energy ⩾100 eV. Our results also agree with the available calculations
for CH4 and C2H2 which employed full molecular wavefunctions beyond 100 eV. Our absorption cross sections also agree with molecular wave-function
calculations for C2H2 and CH4 beyond 100 eV. We have shown the Bethe plots fore
+−C ande
+−H scattering systems and Bethe parameters have been extracted. We have fitted the cross section for positron impact on hydrocarbons
in the formσ
t(C
n
H
m
)=naE
−
b+mcE
−
d in the energy range 300–5000 eV wherea=195.0543,b=0.7986,c=371.1757 andd=1.1379 withE in eV andσ
t in 10−16 cm2. 相似文献
9.
The electron-impact ionization of calcium atoms is studied in the near-threshold energy range (from 6.11 to 16 eV). Experiments
were performed by the method of intersecting electron and atomic beams with the recording of formed positive calcium ions.
The electron beam (ΔE
1/2 = 0.15 eV) was formed using a hypocycloidal electron monochromator. An analysis of the specific features of ionization cross
sections revealed a contribution from the excitation and decay of low-lying autoionization atomic states, which converge to
the excitation thresholds of the 3d, 4p, and 5s ionic levels, and resonances (long-lived states of negative ions). The specific features of cross sections are identified
using the experimental and theoretical data on photoionization (photoabsorption). 相似文献
10.
V. A. Khryachkov I. P. Bondarenko B. D. Kuzminov N. N. Semenova A. I. Sergachev 《Physics of Atomic Nuclei》2012,75(4):404-410
The cross section for the reaction 20Ne(n, α)17O was measured in the neutron-energy range 4–7 MeV. An ionization chamber equipped with a Frisch grid combined with a pulse-shape
digitizer was used as a detector. Gaseous neon that served as a target on which the reaction being studied proceeded was added
to the gas filling the ionization chamber. The partial cross sections for the α
0, α
1, α
2, and α
3 channels of the reaction 20Ne(n, α)17O were obtained for the first time. 相似文献
11.
The X-ray satellite spectra arising due to 2p
3/2
−13x
−1−3x
−13d
−1 (x ≡ s, p, d) transition array, in elements with Z = 40 to 48, have been calculated, using available Hartree-Fock-Slater (HFS) data on
1s
−1−2p
−1 3x
− and 2p
3/2
−1−3x
−1,3x
−1 Auger transition energies. The relative intensities of all the possible transitions have been estimated by considering cross
— sections for the Auger transitions simultaneous to a hole creation and then distributing statistically the total cross sections
for initial two hole states 2p
3/2
−1−3x
−1 amongst various allowed transitions from these initial states to 3x
−1 3d
−1 final states by Coster-Kronig (CK) and shake off processes. In both these processes initial single hole creation is the prime
phenomenon. Each transition has been assumed to give rise to a Gaussian line and the overall spectrum has been computed as
the sum of these Gaussian curves. The calculated spectra have been compared with the measured satellite energies in Lα1 spectra. Their intense peaks have been identified as the observed satellite lines. The peaks in the theoretical satellite
spectra were identified as the experimentally reported satellites α3, α4 and α5, which lie on the high-energy side of the Lα1 dipole line. 相似文献
12.
We study the double ionization of the atomic K-shell by a single photon in the relativistic energy domain. The differential and total cross sections of the process are
calculated. It is shown that the ratio of the cross sections of double and single ionization increases with the photon energy,
tending to the limit 0.34/Z
2, where Z is the atomic number or the nuclear charge. The formulas are found to be valid for Z≫1 and αZ≪1, where α=1/137 is the fine-structure constant.
Zh. éksp. Teor. Fiz. 114, 1537–1554 (November 1998) 相似文献
13.
A. B. Voitkiv 《Journal of Experimental and Theoretical Physics》1997,85(6):1074-1080
Ionization of hydrogen and helium atoms is studied for the case of “soft” collisions with highly charged fast ions with v≲Z≪v2 and v≫v
0, where Z is the ion charge, v is the collision velocity, and v
0∼1 is the characteristic velocity of the electron in the ground state of the atom. Analytical expressions are derived for
the singly and doubly differential cross section for ionization of a hydrogen atom accompanied by the ejection of a slow electron
v
e≲v
0, where v
e is the velocity of the ejected electron with respect to the recoil ion). The results are generalized to the case of single
ionization of helium. It is shown that soft collisions provide the main contribution to the hydrogen ionization cross section
and for all practical purposes determine the cross section for single ionization of helium. The asymmetry in the angular distribution
of the ejected slow electrons and the properties of momentum exchange in such collisions are discussed. Finally, a formula
for the cross section for single ionization of helium is proposed.
Zh. éksp. Teor. Fiz. 112, 1966–1977 (December 1997) 相似文献
14.
Huang Zhiwei Chia Teck Chee Diong Cheong Hoong Lee Sing Zheng Wei Chen Jinkai 《Applied physics. B, Lasers and optics》1998,66(4):471-474
1 Π→X1Σ+ transitions and the continuum spectrum of d3Π→a3Σ+ transitions of the NaK dimer in a heat pipe could be observed in the range of 500–700 nm. The collision-induced enhancement
effects of the intensities Id→a and the quenching effect of the intensities ID→X by collisions with argon buffer gas at different pressures were measured experimentally. Based on the stationary collisional
model and lifetime measurements, the quenching cross sections and cross sections for collision-induced energy transfer between
the D1Π and d3Π states could be estimated.
Received: 13 January 1997/Revised version: 20 October 1997 相似文献
15.
Our previous theoretical work one
− − H2O scattering has been modified and extended to intermediate and high energiesE
i. Using the Bethe plot, we compare the present inelastic cross-sections with the experimental ionization cross sections. Total
cross-sections are analytically represented asQ
TOT(cm2)=a.(E
ieV)
−b
and the parameters ‘a’ and ‘b’ are discussed for molecules H2O, NH3 and CH4 in the rangeE
i=100–1000eV. 相似文献
16.
S. Kumari S. N. Chatterjee L. K. Jha B. N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(2):355-363
H+ impact single and He2+ impact single and double electron
capture cross sections of magnesium atoms have been calculated in the
modified binary encounter approximation (BEA). The accurate expressions of
ion impact sDE\sigma _{\Delta {E}} (cross section for energy transfer
DE\Delta E) and Hartree-Fock momentum distributions of the target
electrons have been used throughout the calculations. On the basis of the
present work it is concluded that inner shell captures by H+ and
He2+ ions incident on magnesium atoms contribute partly to single
electron capture and partly to transfer ionization cross sections. The
calculated He2+ impact double electron capture cross sections of
magnesium are in reasonably good agreement with the experimental
observations. This indicates the success of the present theoretical approach
in study of charge transfer cross sections of atoms as indirect mechanisms do
not interfere with double electron capture processes in this case. 相似文献
17.
M. Ya. Amusia R. Krivec E. Z. Liverts V. B. Mandelzweig 《Journal of Experimental and Theoretical Physics》2006,102(4):556-561
We discuss the results of the calculation of the photoionization with deexcitation of excited He and helium-like ions Li+ and B3+ at high but nonrelativistic photon energies θ. Several lower 1
S and 3
S states are considered. We present and analyze the ratios R
d
+
* of the cross sections of photoionization with deexcitation, σ
(d)
+
*(θ), and of the photoionization with excitation, σ+*(θ). The dependence of R
d
+
* on the excitation of the target object and the charge of its nucleus is presented. In addition to theoretical interest,
the results obtained can be verified using long-lived excited states such as 23
S of He.
The text was submitted by authors in English. 相似文献
18.
On the basis of the total cross sections for neutron-proton scattering in the region of laboratory energies below 150 keV,
the value of σ0 = 20.4288(146) b was obtained for the total cross sections for neutron-proton scattering at zero energy. This value is in
very good agreement with the experimental cross sections obtained by Houke and Hurst, but it is at odds with Dilg’s experimental
cross section. By using the value that we found for σ0 and the experimental values of the neutron-proton coherent scattering length f, the deuteron binding energy ɛ
t
, the deuteron effective radius ρ
t
(−ɛ
t
, −ɛ
t
), and the total cross section in the region of energies below 5 MeV, the following values were found in the shape-parameter
approximation for the low-energy parameters of neutron-proton scattering in the spin-triplet and spin-singlet states: a
t
= 5.4114(27) fm, r
0t
= 1.7606(35) fm, v
2t
= 0.157 fm3, a
s
= −23.7154(80) fm, r
0s
= 2.706(67) fm, and v
2s
= 0.491 fm3. 相似文献
19.
I. D. Petrov V. L. Sukhorukov M. W. Ruf H. Hotop 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(3):289-302
Absolute photoionization cross sections for Ne atoms in the excited
levels (Paschen notation
) were calculated at near threshold energies within
the configuration interaction Pauli-Fock approach including core polarization.
The computed spectra and the lineshape parameters of the odd parity
2p1/2
5ns′/d′ autoionizing resonances are
found to be in good agreement with high resolution laser spectroscopic
results. Guided by the theoretical results, improved analyses of the measured
spectra by superimposed Fano-type profiles were achieved. Theoretical
predictions are presented for resonances which have not yet been studied
experimentally. In addition, we report the absolute partial photoionization
cross sections for the 2P3/2 and 2P1/2 channel at
photoelectron energies up to 7 eV. Except for the highest lying 2p1(1S0) level, these cross sections monotonically decrease with
energy (as reported earlier in single-electron calculations for the
Ne(2p53p) configuration) with branching ratios which essentially reflect
the core composition of the 2px levels. For the 2p1 level the resonance structure and the
partial cross sections are strongly influenced by a
Cooper-Seaton minimum in the d3/2
′ channel,located just above the 2P1/2 ionization limit. 相似文献
20.
V. E. Tarasov V. V. Khabarov A. E. Kudryavtsev V. M. Weinberg 《Physics of Atomic Nuclei》2008,71(8):1410-1423
The Kd reactions are considered in the impulse approximationwithNN final-state interactions (FSI) taken into account. Realistic parameters for the KN phase shifts are used. The “quasi-elastic” energy region, in which the elementary KN interaction is predominantly elastic, is considered. The theoretical predictions are compared with the data on the K
+
d → K
+
pn, K
+
d → K0
pp, K
+
d → K
+
d, and K
+
d total cross sections. The NN FSI effect in the reaction K
+
d → K
+
pn has been found to be large. The predictions for the Kd cross sections are also given for slow kaons, produced from ϕ(1020) decays, as the functions of the isoscalar KN scattering length a
0. These predictions can be used to extract the value of a
0 from the data.
The text was submitted by the authors in English. 相似文献