锡和氙离子在13.5 nm波长附近的光谱特性

 应用多组态Dirac-Fock方法,系统计算了锡（Sn）和氙（Xe）离子在13.5 nm波长附近的辐射跃迁波长和跃迁几率。深入分析了^(7~13)+Sn和Xe^(7~13)+离子跃迁的原子光谱特性,研究了相对论效应和电子关联效应对能级位置和跃迁几率的影响发现,相对论效应和电子关联效应对光谱能量的影响分别为2%和5%。并从光谱特性的角度对比讨论了Sn和Xe作为极端远紫外光源的优劣,发现Sn更有优势。     

Charge-state resolved above threshold ionization

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.     

稀有气体在电离区压缩特性研究

采用Saha方程加Debye-Hückel修正简单近似模型,给出了稀有气体He, Ne, Ar, Kr, Xe在电离区的物态方程以及离化度.计算结果与已有实验和理论计算进行比较,验证了模型的可靠性.通过对稀有气体等温和冲击压缩特性理论分析,讨论了其压缩和电离的规律性.论证了在稀有气体He, Ne, Ar, Kr, Xe中,气体Xe具有较好的抗压缩性.     

Spectroscopy of mixed Ar-Xe clusters: Formation of a xenon core

The spectra of vacuum ultraviolet luminescence of heteroatomic Ar-Xe clusters condensed in supersonic jets of a mixture of these gases at a xenon impurity concentrations of 0.001–2% are measured. A new group of molecular luminescence bands of argon-xenon centers is recorded, which allows a highly sensitive detection of xenon in the argon matrix of a cluster. The phenomenon of phase separation into pure components with formation of a sharp interface between the xenon core and argon shell of the cluster is found.     

L x‐ray transitions in F‐like to Na‐like xenon ions determined at a room temperature electron beam ion trap

Fluorine‐like to sodium‐like xenon ions were investigated by wavelength‐dispersive x‐ray spectrometry at the Dresden Electron Beam Ion Trap (EBIT) working at room temperature. In addition to the precise measurement of the L x‐ray transition energies following ionization, excitation and recombination processes in the highly charged xenon ions, the spectra were analyzed for different gas pressures in the trap. Multiconfiguration Dirac‐Fock calculations are introduced that were applied to the energies, transition probabilities and excitation cross‐sections. The production of neon‐like xenon ions was demonstrated even at very high gas pressures. Copyright © 2005 John Wiley & Sons, Ltd.     

Ar+ and Xe+ velocities near the presheath-sheath boundary in an Ar/Xe discharge

The velocities of Ar+ and Xe+ ions near the presheath-sheath boundary in an Ar/Xe discharge are studied by particle-in-cell Monte Carlo simulation. For a pure argon discharge the argon ion has almost the same velocity profile as it does in the mixture of argon and xenon. Similarly, for a xenon discharge the xenon ion has almost the same velocity profile as it does in the mixture of argon and xenon. The ion speed at the sheath-presheath boundary is the same for an ion in a pure argon or xenon discharge and for the same ion in a mixture of argon and xenon. We conclude that, in our simulation, each ion reaches its own Bohm speed at the presheath-sheath interface.     

Obtention des bandes de cameron par photo excitation de co en matrices d'argon de krypton et de xenon

CO trapped in solid matrices of argon, krypton and xenon has been excited by 10 eV photons. Cameron bands v′=0, v″=0,1,2,3,4 are observed during the irradiation. If red shifts are observed in argon and krypton matrices, the transition in xenon shows no differences with gas phase data.     

Transitions and level lifetimes in Ne II, III, Ar II, III, Kr II, III and Xe II

Beam-foil spectra of neon, argon, krypton, and xenon have been recorded photographically with a fast spectrograph. The particle energies ranged from 150 to 750 keV. Transitions in Ne II, III; Ar II, III; Kr II, III; and Xe II have been identified. In addition, new multiples were identified in Ne II and Xe II and a number of unidentified lines were observed in neon, argon, and krypton. Characteristic intensity decays of over 170 lines were measured, giving the mean lives of ≈ 80 levels, with an estimated error of 30 per cent. Tabulation of energy levels with similar electron configurations in neon, argon, krypton, and xenon shows a definite progression to larger mean lives as the nuclear change increases.     

Observations of extreme ultraviolet emission from plasma produced by capillary discharges

This study reports the results of a pilot experiment concerning observations of extreme ultraviolet emission from plasma produced by the capillary discharges. A few kA current was applied across the gas-filled alumina capillary (1 mm diameter and 8 mm long) to generate radiation in the EUV region (12–63 nm). Spectroscopic studies were carried out by means of a XEUV spectrometer which was upgraded for special lithography purposes. The results obtained from the EUV spectroscopic measurements provided information about the radiation processes from xenon and argon plasma and testifies that given capillary is an effective source of EUV emission. Additionally we showed a simulation which describes plasma dynamics parameters and dynamics of various ionization stages in capillary discharge. Our computer simulation confirmed the presence of ions, which spectra was registered in the experiment.     

Transport properties and weak non-ideality in xenon and argon plasmas of intermediate degree of ionization

Electron mobility and electric conductivity in xenon and argon plasmas of various degrees of thermal ionization are evaluated with the aid of a revised definition of the Debye radius permitting to treat these plasmas formally as weakly non-ideal. The analysis is carried out for temperatures ranging from 2 000 K to 20 000 K and for various initial pressures, equal to or smaller than the normal atmospheric pressure.     

Multiple inner-shell ionization in oxygen produced by ion bombardment in the MeV range

Oxygen X-ray spectra from oxide targets by proton, helium, nitrogen and argon ion bombardment are studied. K satellite and hypersatellite peaks are observed. In light ion bombardment, X-ray production of the double K-shell ionization indicated large deviation from the Z²₁ dependence.     

Electron production by metastable rare gas atom impact on a molybdenum (110) surface

Electron production by impact of thermal energy metastable helium, argon, and xenon atoms on a molybdenum (110) surface was studied. The electron yield was always highest for a clean surface and decreased considerably when the surface was exposed to either oxygen or carbon monoxide. The change in electronic yield with gas coverage of the surface was most drastic for xenon and smallest for helium metastables. The similarity of the present results to earlier measurements of electron production by low energy noble gas ion impact led us to believe that metastable deexcitation proceeded via resonance ionization followed by Auger neutralization in the present cases.     

A study of the global chirp dependence on the interaction of intense colored double pulses with clusters

The yields of highly charged atomic ions produced in the exposure of xenon clusters embedded in helium nanodroplets by intense colored double pulses show a notable sensitivity on the order of the subpulses. The only slight difference in their spectral composition leads to a flipping of the optimal laser parameters for effective multielectron ionization above certain charge states, which appears to be quite robust with respect to the chosen pulse fluence and reflects an avalanche-like developing cluster ionization scenario.     

Van der Waals molecules and collision pairs of noble-gas atoms ahead of a shock wave front

The effect of creation of an excess concentration of free electrons in an anomalously thick layer (≈5 cm) ahead of an explosively driven shock wave in noble gases is discussed and interpreted. This effect is the ionization of excited 1_u-state molecules produced due to the absorption of a small intensity flux (as compared to the ionization one) of photons (with energies substantially lower than the atom ionization threshold) by unexcited colliding complexes and van der Waals molecules. A model is proposed which explains the excitation of xenon molecules ahead of the radiationless shock wave of an open discharge. The absorption spectra of colliding complexes and van der Waals molecules adjacent to each other near the atomic absorption lines can be resolved into two spectra, and these spectra can be changed by an increase in gas temperature. As a result, radiation capable of exciting van der Waals molecules penetrates through the shock wave of an open discharge and excites xenon molecules there. The present work develops further the knowledge concerning the radiation energy transport in the shock wave front. It also proves that in front of an explosively driven shock wave a great number of excited molecules of noble gases are actually formed, and this means considerable progress toward a VUV laser with optical pumping. Translated from Preprint No. 56 of the P. N. Lebedev Physical Institute, Moscow, 1993.     

Generation of femtosecond vacuum-ultraviolet pulses

High power femtosecond pulses in the Vacuum Ultra Violet (VUV) have been generated through the nonlinear interaction of femtosecond KrF pulses with xenon and argon gas. Under near resonant two photon excitation of xenon by a femtosecond KrF laser, parametric four wave mixing processes lead to VUV pulses at 147 and 108 nm with pulse energies in the 10 µJ range. Tuning is demonstrated by mixing the KrF pulse with a 500 fs dye laser pulse at 497 nm, resulting in 165 nm emission. In argon, a three photon resonance leads to third harmonic generation at 83 nm and micro joule level pulses near 127 nm generated by a six wave mixing process. Since the spectra of the VUV pulses show an ionization-induced blue shift with increasing KrF laser intensity, the VUV pulses can be shown to have temporal duration less than the pulse width (450 fs) of the KrF laser. Blue shifting of the third harmonic of the KrF laser in argon is dominated by a reduction in the neutral gas density rather than by an increase in the electron density.     

双驱动x射线激光等离子体能谱特性研究

用时间积分空间分辨的平晶千电子伏谱仪测量了钽激光等离子体发射波长范围为045— 075nm的软x射线能谱，精确测量和准确辨认出类镍、类钴和类铁离子的共振线及类镍离子 的内壳层跃迁线-对实验结果处理，获得了辐射线谱的强度-通过谱线比率的诊断推断脉冲激 光时差对等离子体状态的影响，至少也可部分解释激光上能级的粒子数及等离子体的 电离程度- 关键词： 离子谱特性 软x线能谱强度 谱线辨认     

Effect of long-range intermolecular forces on the drag of an oscillating disk and on the viscosity of gases

An experimental investigation has been made to determine the changes produced by ionization in the apparent viscosity of gases. The method used is that of the oscillating disk. In one series the gas was ionized by the gamma rays from an externally placed cesium-137 source. In the other two series of measurements the ionization was achieved with the aid of the alpha particles emitted from the surface of the oscillating disk coated with polonium 210.The measurements were made on nine gases at room temperature and in the pressure range of 1 mm Hg to 1.7 atm. The gases were: dry air, nitrogen, carbon dioxide, oxygen, helium, neon, argon, krypton and xenon. The experimental results showed that there is a very small change in the skin friction experienced by the disk.     

Generation of attosecond pulses in molecular nitrogen

We investigate the carrier-envelope phase dependence of the total ionization yield for single and double ionization of xenon. We compare our results to theoretical calculations and to the phase dependent asymmetry in photoelectron emission. We observe that the phase dependence of the photoion yields, regardless if single or double ionization, is at least 2-3 orders of magnitude below the photoelectron emission signal. We conclude that total photoionization yields are only very weakly dependent on the carrier envelope phase, and that they are not a useful means for measurement of the phase. It seems possible that the broad bandwidth of few-cycle pulses facilitates multiphoton ionization, which leads to a randomization of strong field ionization phase dependencies. Besides, we observe that the spatial asymmetry in photoelectron emission appears to be useful as an indicator for the laser pulse duration in the few cycle regime.     

Fluorescence polarization of helical molecules cooled in a supersonic jet

The β-binaphthylene oxide molecules studied under supersonic cooling conditions have a number of specific properties due to their nonplanarity. Low-frequency vibrations of the molecules in the excited S1 state are higher than the frequencies for the S0 state, and conversely the high-frequency vibrations have lower frequencies. The S₀-S₂ fluorescence excitation spectrum is structureless. The absence of a Q branch in the rotational contour of the line for the purely electronic transition indicates that it is substantially broadened and shifted toward shorter wavelengths as a result of rotational perturbations of the helical structure of the molecule. Multiplet lines in the spectra of β-binaphthylene oxide complexes with argon, krypton, and xenon correspond to different isomeric complexes. Their bond energies are below those observed previously for planar polycyclic molecules such as perilene, fluorene, and carbazole. The greater number of isomers with xenon is due to strengthening of the bond in the van der Waals complex and the nonequivalence of the position of the xenon atoms on the outside and inside of the helical molecule. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 473–477, July–August, 2006.     

Electron energy spectra from intense laser double ionization of helium

The double ionization of helium in the strong-field limit has been studied using an electron-ion coincidence technique. The observed double ionization electron energy spectra differ significantly from the single ionization distributions. This gives new support to the rescattering model of double ionization and explicitly reveals the role of backward electron emission following the e-2e ionizing collision.