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1.
Absolute single and double ionization cross sections of neon 2s- and 2p-subshells for proton (40–900 keV) and electron impact (0.2–10 keV) have been measured using photon spectroscopy in the spectral range of the vacuum ultraviolet. Cross sections for double ionization decrease more rapidly with increasing impact energy than cross sections for single ionization. No definite asymptotic energy dependence of a Bethe-Fano-plot could be found for double ionization in contrast to single ionization. The experimental results are compared with theoretical predictions of the shake-off model and Gryzinski's classical binary encounter theory. Better agreement is found with the latter, indicating that successive binary collisions have to be considered as a strong mechanism for double ionization by protons or electrons of the investigated energy range. Comparison is made with other experimental results for double ionization by photon impact or capture ionization by proton impact. 相似文献
2.
In this work, we present ab initio computations of the interaction of helium and lithium with a strong laser field. By computing the two-and three-particle wave functions, we retain the full electron correlation and numerically integrate the time-dependent Schrödinger equation (TDSE) restricted to one dimension. The correlated nonsequential double ionization (NSDI) and the sequential double ionization (SDI) is studied. Our results show a clear transition from NSDI to SDI for increasing intensities. The correlated double ionization is found to be sensitive to the spin configuration of the ionized pair. Our model allows us to “measure” two different channels of double ionization (one with both spins aligned and one with spins antialigned). 相似文献
3.
C. Ruiz L. Plaja J.R. Vázquez de Aldana L. Roso 《Applied physics. B, Lasers and optics》2004,78(7-8):829-833
We investigate the double ionization of helium under an intense laser pulse. This process is known to be one of the prototypical manifestation of electron–electron correlation. In this work, we present a numerical study on the influence of Paulis exclusion principle in the double ionization. We make a comparative analysis of two almost degenerated states with different character with respect to the exchange symmetry. We show that there exists a significant difference in the double ionization of parahelium and orthohelium. The symmetric character of the spatial electronic wavefunction affects strongly double ionization. It is found that the double ionization is partially suppressed in the orthohelium case. The mechanisms relevant for this suppression are discussed. PACS 31.15.Ar; 31.25.Jf 相似文献
4.
《中国物理快报》2016,(4)
We experimentally investigate the double ionization of molecular hydrogen subjected to ultrashort intense laser pulses.The total kinetic energy release of the two coincident H~+ ions,which provides a diagnosis of different processes to double ionization of H_2,is measured for two different pulse durations,i.e.,25 and 5fs,and various laser intensities.It is found that,for the long pulse duration(i.e.,25 fs),the double ionization occurs mainly via two processes,i.e.,the charge resonance enhanced ionization and recollision-induced double ionization.Moreover,the contributions from these two processes can be significantly modulated by changing the laser intensity.In contrast,for a few-cycle pulse of 5fs,only the recollsion-induced double ionization survives,and in particular,this process could be solely induced by the first-return recollision at appropriate laser intensities,providing an efficient way to probe the sub-laser-cycle molecular dynamics. 相似文献
5.
Study on Non-Sequential Double Ionization of Aligned Diatomic Molecules in Strong Laser Fields 下载免费PDF全文
We develop a semiclassical model to describe the non-sequential double ionization of aligned diatomic molecules in an intense linearly polarized field. It is found that in the tunnelling regime, the oriented molecule shows geometric effects on double ionization process when aligned parallel and perpendicular to the external field. Our results are qualitatively consistent with the recent experimental observations. 相似文献
6.
The double ionization of lithiumlike ions by Compton scattering of photons is investigated in the asymptotic high-energy region. To leading order of the nonrelativistic perturbation theory, the total cross section for double Compton effect is calculated, taking into account the channels of simultaneous and sequential emission of two electrons. Relationships between the cross sections for double ionization of He- and Li-like ions with the same nuclear charge Z are established. This can open wide perspectives for experimental investigations of ionization processes involving low-lying excited states. The universal scaling is found for the ratio of double-to-single ionization in the lithium isoelectronic sequence. 相似文献
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8.
The manifestation of double resonances upon the three-photon ionization of the samarium atom has been studied in a frequency
range of 17200–18400 cm−1. Thirty peaks caused by double resonances have been found in the dependence of the yield of Sm+ ions on the laser radiation frequency. The majority of these peaks greatly exceed in amplitude the peaks associated with
ordinary two-photon resonances. The influence of double resonances on the three-photon ionization has been theoretically analyzed
using the density matrix approximation. The calculations show that the probability of the three-photon resonance ionization
can increase by more than two orders of magnitude due to the additional one-photon population of an intermediate level. The
double resonance slows down the rate of increase in the probability of ionization with an increase in the laser radiation
intensity compared to ordinary two-photon resonance. 相似文献
9.
Double ionization of H_2 in a co-rotating two-color circularly polarized(TCCP) laser field is theoretically investigated. By changing the ratio of electric field peak amplitudes of the TCCP laser pulses, the double ionization probability as a function of the laser intensity shows a clear knee structure, which is suppressed significantly in the case of the atom. Due to the large spatial range of the electronic initial distribution, with the analysis of classical trajectories of ionized electrons, it is found that the ionization of the electron in the farther distance increases the probability of recollision. Furthermore, the yield of nonsequential double ionization created by the recollision can be enhanced by controlling the amplitude ratio of the TCCP laser field. 相似文献
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11.
Photoelectron energy resolved spectra recorded in coincidence with singly and doubly ionized atoms are reported for the interaction of xenon with 60 fs laser pulses at 800 nm and 1x10(14) W/cm(2). Double ionization contributions in the spectrum have been established. The appearance of a single ionization plateau in above threshold ionization is verified. A hotter electron distribution is found for the double ionization. 相似文献
12.
We present total cross sections for single and double ionization of helium by antiproton impact over a wide range of impact energies from 10 keV/amu to 1 MeV/amu. A nonperturbative time-dependent close-coupling method is applied to fully treat the correlated dynamics of the ionized electrons. Excellent agreement is obtained between our calculations and experimental measurements of total single and double ionization cross sections at high impact energies, whereas for lower impact energies, some discrepancies with experiment are found. At an impact energy of 1 MeV we also find that the double-to-single ionization ratio is twice as large for antiproton impact as for proton impact, confirming a long-standing unexpected experimental measurement. 相似文献
13.
Quantum calculations of a (1+1)-dimensional model for double ionization in strong laser fields are used to trace the time evolution from the ground state through ionization and rescattering to the two-electron escape. The subspace of symmetric escape, a prime characteristic of nonsequential double ionization, remains accessible by a judicious choice of 1D coordinates for the electrons. The time-resolved ionization fluxes show the onset of single and double ionization, the sequence of events during the pulse, and the influences of pulse duration and reveal the relative importance of sequential and nonsequential double ionization, even when ionization takes place during the same field cycle. 相似文献
14.
《等离子体物理论文集》2017,57(3):99-105
The characteristics of low‐frequency oscillations of double‐stage Hall thrusters are quite different from those of conventional single‐stage Hall thrusters. In this paper, the effects of double‐stage discharge on the low‐frequency oscillations are experimentally investigated. The results indicate that the amplitude significantly decreases with increasing magnetic field strength and voltage during the ionization stage. Meanwhile, data analysis reveals that ionization occurs in both stages and that the transport ion current between the two stages is the key factor that affects the amplitude and main frequency of the oscillations. Two new processes, namely the ion transport and ion recombination caused by double‐stage discharge, are found to be relevant to the change in the current oscillations. To summarize, the ionization stage relieves the oscillations in the acceleration stage, leading to a reduction in the amplitude of the discharge current. 相似文献
15.
The binary encounter approximation has been used for calculations of electron impact single ionization cross-sections for
F, Cl, Br and I and double ionization cross-sections for Br and I. Contributions of ionization from inner shells have also
been included in the calculations. Hartree-Fock momentum distribution has been used for the bound electron as far as possible.
The results have been found to be in satisfactory agreement with experimental observations. 相似文献
16.
The production of high-momentum electrons in double ionization of helium by near-infrared lasers is investigated using three-dimensional classical ensembles. The nucleus' role is examined by systematically adjusting the nuclear potential. The primary source of the high-energy electrons is found to be backscattering off the nucleus at recollision. Recollision excitation with backscattering of the unbound electron is found to be especially important. It is shown that recollision excitation with ionization before the next field maximum can lead to a correlated electron pair. 相似文献
17.
R. I. Campeanu M. Alam 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(1):19
The ionization of the 3p orbital of argon by 60 and 100 eV incident
positrons is studied with the DWBA approximation. The variation of our double differential
ionization cross sections with scattered positrons energy is found to be in reasonable
agreement with the experiment. 相似文献
18.
L.K. Jha B.N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):5-10
Electron impact single and double ionization cross-sections for magnesium have been calculated in the binary encounter model
using accurate expression for (cross-section for energy transfer ΔE) as given by Vriens. Hartree-Fock velocity distributions for the target electrons have been used throughout the calculations.
In case of double ionization contributions of inner shell ionization and Auger emission have been included in the present
work. The results obtained in case of single ionization are excellent and at the same time the double ionization cross-sections
show reasonably good agreement with the recent experimental observations. Substantiation of the viewpoint of Peach, and Boivin
and Srivastava that a vacancy in the 2p shell of magnesium leads to double ionization is a remarkable feature of the present investigation.
Received 9 October 2001 / Received in final form 8 January 2002 Published online 28 June 2002 相似文献
19.