等离子体密度对放电等离子体极紫外光源影响研究

等离子体状态是决定极紫外光源功率和转换效率的最重要因素之一,理论和实验研究上Xe气流量对放电等离子体极紫外光源辐射谱和等离子体状态的影响,对于优化光源工作条件具有重要的意义。理论上,采用碰撞-辐射模型,模拟了非局部热力学平衡条件下,不同电离度的离子丰度分布随电子温度和离子密度的变化。推导了Xe8+~Xe11+离子4d-5p跃迁谱线强度随电子温度的变化趋势。实验上,采用毛细管放电机制,利用罗兰圆谱仪测量和分析了不同等离子体密度条件下,放电等离子体极紫外光谱的变化,分析了Xe气流量对等离子体状态的影响。理论和实验结果表明： 相同的电流条件下,等离子体箍缩时的平均电子温度随着Xe气流量的增加而降低。对于4d-5p跃迁,低电离度离子与高电离度离子谱线强度的比值随着温度的增加而减少。电流28 kA、Xe气流量0.4 sccm(cm3·min-1)时,等离子体Z 箍缩平均电子温度位于29 eV附近。Xe气流量增加时,受离子密度和最佳电子温度的影响,实现Xe10+离子4d-5p跃迁13.5 nm(2%带宽)辐射谱线强度最优化的Xe气流量位于0.3~0.4 sccm之间。     

Dynamics and post-collision interaction effects in two electron decay from the Xenon 4d hole

Two Auger electrons, one very slow, one fast, have been detected in coincidence following near threshold 4d photoionization of the Xe atom. The distribution in the energy the two electrons share has been measured for the first time revealing the presence of post-collision interaction effects that provide unique information on the decay dynamics of the 4d hole. Analysis of the distorted line shapes indicates that the dominant process is decay of Xe+(4d(-1)) to Xe3+ through cascade emission of a zero kinetic energy Auger electron followed by a fast Auger electron. The widths of the intermediate Xe2+* states are estimated to be about 60 meV.     

Correlation between double and nonresonant single ionization

We performed simultaneous measurements of electrons and ions produced in Xe photoionization driven by an 800-nm, 100-fs laser pulse. The obtained energy and angular resolved electron spectra allow the identification of the electronic states populated during the ionization. Xe2+ ions appear at the same laser intensity as electrons emerging from a nonresonant 9-photon ionization process of Xe. Similar to optical tunneling ionization, the nonresonant ionization delivers low-energy electrons needed for the formation of Xe2+ by a backscattering process.     

Double photoionization into double core-hole states in Xe

Double photoionization (DPI) leading to double core-hole states of Xe2+ 4d(-2) has been studied using a magnetic bottle time-of-flight spectrometer. The assignments of the Xe2+ 4d(-2) states are confirmed by the Auger lines extracted from fourfold coincidences including two photoelectrons and two Auger electrons. It is estimated that the core-core DPI into Xe2+ 4d(-2) at a photon energy of 301.6 eV has a favored cross section of about 0.3 MB. The intense core-core DPI is due to mixing of the 4d(-2) continuum with the 4p single photoionization, which is manifested in the relative intensities of the Xe2+ 4d(-2) components.     

Many-electron dynamics of a Xe atom in strong and superstrong laser fields

We report on detailed investigations of ionization dynamics of a Xe atom exposed to intense 800-nm pulses of 20-fs duration in the extensive intensity range from 10(13)-10(18) W/cm(2). Ion yields of Xe+-Xe20+ were observed as a function of laser intensity and compared with the results from a single active electron based Ammosov-Delone-Krainov model. Unexpected ionization probabilities for lower charge states and no interplay between the inner and outer shells by screening are inferred. Suppression of nonsequential ionization towards higher intensity and few optical cycle regimes is also proved.     

HCl＋Xe掺杂CO矩阵晶体中Xe＋2Cl－电子态跃迁

报道ＨＣｌ＋Ｘｅ掺杂ＣＯ矩阵晶体中，在３０８ｎｍ激光的激发下，首次观测到准分子Ｘｅ＋２Ｃｌ－的特征辐射荧光谱。双光子诱导电荷转移合作吸收反应：Ｘｅ＋ＨＣｌ＋２ｈν→αＸｅ＋（ＨＣｌ）－中，双光子吸收截面大于５×１０－４２ｃｍ４ｓ［６］。     

Radiative Characteristics of Xe2Cl* Molecules under High-Energy Electron Pumping of Xe–CCl4 and Ar–Xe–CCl4 Gas Mixtures with a Low CCl4 Content

Optics and Spectroscopy - Spontaneous and stimulated emissions of Xe2Cl* triplex molecules upon excitation of Xe–CCl4 gas mixtures with a low CCl4 content by a pulsed high-energy electron...     

High-resolution spectrum of xenon ions at 13.4 nm

The spectrum of xenon excited in a low-inductance vacuum spark was photographed at high resolution in the region of 9.5-15.5 nm. The observed transitions were identified as belonging to ions from Xe8+ to Xe13+. In the region of importance for extreme-ultraviolet lithography around 13.4 nm, the strongest lines were identified as 4d8-4d7 5p transitions in Xe10+. The identifications were made by use of energy parameters extrapolated along the isoelectronic sequence.     

An XeCl* Excimer Fluorescence Study on the Pulse Radiolysis of Xe–nCCl4 and Xe–SOCl2 Systems

The mechanism and kinetics of energy transfer from highly excited Xe states (E _ex > 9.5 eV), generated by a 12-ns electron beam, to chlorine donor molecules were deduced from time-resolved spectra of fluorescence in the region 240–340 nm. The emissions at 240–250 nm were assigned to Xe₂** excimers, and those at 308 and 340 nm to XeCl(B) and XeCl(C) states. Kinetic analysis of the recorded spectra for Xe–CCl₄ and Xe–SOCl₂ gas mixtures at constant xenon pressure and various pressures of molecular admixtures (0.1–1 Torr) allowed us to find the rate constants for the reactions (5) Xe** + RCI products, (6a) Xe** + RCl XeCl(B) + R*, and (6b) Xe** + RCl XeCl(C) + R*, where R is any radical.     

单晶YSZ的Xe+辐照损伤的电子显微分析

 不同注量200keV Xe⁺ 注入YSZ单晶样品的电子显微分析结果表明，随着辐照注量的增加，缺陷簇的密度增大，在1×10¹⁵~1×10¹⁶cm^-2Xe⁺注量，缺陷簇密度迅速增大，形成间隙型位错环；当Xe⁺注量增大到1×10¹⁷cm^-2，缺陷簇密度的增加变得缓慢，并且有直径为2～4nm的Xe气泡析出。选区电子衍射花样表明YSZ样品没有产生非晶化转变。在Xe⁺辐照的离位率高达约350dpa的情况下，YSZ晶体没有非晶化，其原因主要是由于注入的Xe⁺以气泡形式析出。     

Slow photoelectron imaging

Experiments are reported on the detection of slow photoelectrons resulting from the photoionization of Xe atoms in a dc electric field by electron imaging. In the far-field photoelectron velocity distributions we can distinguish between direct and indirect ionization processes (involving long range Coulomb interactions with the Xe+ ion). Also, a new modulation of the velocity distribution is observed which cannot be explained by previously discussed mechanisms. Classical and quantum mechanical calculations are presented to support the interpretations.     

On the correlation between the composition of Pr doped garnet type materials and their photoluminescence properties

Lu₃(Al,Ga)₅O₁₂ and (Y,Lu)₃(Al,Mg,Si)₅O₁₂ samples doped with 1% Pr³⁺ were prepared by two aqueous sol-gel chemistry approaches, such as citrate and glycolate methods. All samples were characterised by powder X-ray diffraction (XRD), thermal quenching (TQ), fluorescence lifetime measurements and photoluminescence (PL) techniques. It turned out that the Pr³⁺ emission is very sensitive to the composition of the garnet host lattice. Lu₃Al₅O₁₂:Pr³⁺ samples showed mainly [Xe]4f¹5d¹→[Xe]4f² broad band emission in UV-blue region, whereas [Xe]4f²-[Xe]4f² line emission of Pr³⁺ dominated in Lu₃Ga₅O₁₂ samples. Modification of garnet crystals with Mg²⁺-Si⁴⁺ pair has led to generation of strong crystal field strength resulting in energy transfer from 5d to 4f orbitals. Y₃AlMg₂Si₂O₁₂ composition generated the strongest crystal field splitting out of all synthesised samples and showed practically only Pr³⁺ [Xe]4f²-[Xe]4f² line emission in the red spectral region.     

Enhancement of double auger decay probability in xenon clusters irradiated with a soft-x-ray laser pulse

The interaction of large Xe clusters with a soft x-ray laser pulse having a wavelength of 13.9 nm and an intensity of up to 2x10(10) W/cm2 was investigated using a time-of-flight ion mass spectrometer. The corresponding laser photon energy was sufficiently high to photoionize Xe 4d innershell electrons. It was found that Xe3+ ions (which result from double Auger decay of 4d vacancies) became the dominant final ionic product with increasing cluster size and x-ray intensity. This is in contrast to the results of synchrotron radiation experiments involving free Xe atoms, in which Xe2+ is the dominant resultant ion species. Possible mechanisms responsible for the enhancement of the double Auger transition probability in x-ray laser and cluster interaction are discussed.     

Relativistic effects in the variable-screening model

The variable-screening model devised for a quantitative treatment of screening effects in slow (quasimolecular) ion-atom collisions is extended to include relativistic effects. Relativistic correction terms corresponding to a relative energy correction of second order in the electron velocity are incorporated into the effective molecular single-electron Hamiltonian. The model is applied to the calculation of relativistic molecular-orbital correlation diagrams for the quasimolecular systems Br+Br, Xe+Xe, and I+Au. A detailed comparison of our results with the results of relativistic calculations for (unscreened) one-electron systems and calculations based on self-consistent field methods is performed. The agreement with Dirac-Fock-Slater results is fairly good, and could be improved further by read-justing the values of the parameters in the atomic potentials used to construct the effective molecular potential.     

Relativistic effects in the variable-screening model

The variable-screening model devised for a quantitative treatment of screening effects in slow (quasimolecular) ion-atom collisions is extended to include relativistic effects. Relativistic correction terms corresponding to a relative energy correction of second order in the electron velocity are incorporated into the effective molecular single-electron Hamiltonian. The model is applied to the calculation of relativistic molecular-orbital correlation diagrams for the quasimolecular systems Br+Br, Xe+Xe, and I+Au. A detailed comparison of our results with the results of relativistic calculations for (unscreened) one-electron systems and calculations based on self-consistent field methods is performed. The agreement with Dirac-Fock-Slater results is fairly good, and could be improved further by read-justing the values of the parameters in the atomic potentials used to construct the effective molecular potential.     

低速Xe~(q+)(4≤q≤20)离子与Ni表面碰撞中的光辐射

实验中测量了0.38V_(Bohr)(460 keV)高电荷态Xe~(q+)(4≤q≤20)离子轰击高纯Ni表面发射的400-510 nm光谱.实验结果包括NiⅠ原子谱线,NiⅡ离子谱线,以及入射离子中性化发射的XeⅠ,XeⅡ和XeⅢ谱线.研究了谱线XeⅡ410.419,XeⅢ430.444,XeⅡ434.200,XeⅡ486.254,NiⅠ498.245,NiⅠ501.697,NiⅠ503.502,NiⅠ505.061和NiⅠ508.293 nm的光子产额随着入射离子电荷态的变化.结果表明,入射离子中性化和溅射Ni原子发射谱线的光子产额随着入射离子电荷态的增加而增加,其趋势与入射离子势能一致.     

Population processes in high-pressure inert-gas-mixture lasers

Working-level-population processes are analyzed on the basis of detailed investigations of the amplitude-time structure of the laser and spontaneous emission following a pulsed electric discharge in the mixtures He + R (R = Ar, Kr, Xe), Ar + Xe. Account is taken in the analysis of excitation by electrons (direct and stepwise) and of population as a result of relaxation processes (collisions of second kind with electrons; radiative cascades, recombination processes; collisions with the atoms of the working and buffer gases; excitation transfer from helium molecules). It is concluded that under optimum efficiency conditions inversion is produced in the lasers considered as a result of direct electron collision with the working atoms (Ar, Kr, Xe), which are in the ground state.Translated from Lazernye Sistemy, pp. 15–34, 1982.     

Evidence for Fermi-shuttle ionization in intermediate velocity C+ + Xe collisions

Experimental evidence has been found for consecutive projectile-target-projectile (triple) and projectile-target-projectile-target (quadruple) "ping-pong" scattering of ionized target electrons in single C+ +Xe collisions at 150 and 233 keV/u impact energies. Distinct signatures of the multiple electron scattering contributions to the high-energy part (300-3400 eV) of the double differential electron spectra have been separated and identified with the help of reference measurements using He+ projectile ions and different calculations.