In this work we have studied the generation of Extreme Ultraviolet (EUV) light by a novel Compact Electron Cyclotron Resonance Ion Source (CECRIS). The EUV emission diagnostics of the ECR plasma was accomplished by means of a 1.5 m Grazing Incidence Monochromator which was operated in a wavelength range of 4-90 nm under the condition of medium to high resolution to discriminate between spectra arising from different Xeq+ (q = 1-10) charge states. One of the major accomplishments of this study is assignment of numerous new optical transitions for Xenon in the 10-80 nm range under absolute conditions to create a database for further investigations. High resolution spectra were recorded confirming fair contributions from highly excited Xe10+ and Xe9+ ionic states. Major outcome of this work is that the Xe10+ ion emission with λ = 13.4 nm may occurs with such a simplified and compact ECR source. The EUV emission of this particular line is of great interest for lithography applications.
We report intensive experimental and theoretical data corresponding to helium extreme ultraviolet (EUV) emission in the 30-60 nm wavelengths range for e- + He, H+ + He, and Hn+ + He (n=2-3) collisions with impact velocities from 1.4 to 8.5 a.u. Specifically, the degree of linear polarization associated with HeI (1snp) 1Po levels, n=2-5, (λ=51.7 to 58.4 nm for n=2-5 to n=1 transitions) and HeII (2p) 2Po states (λ=30.4 nm) have been measured at intermediate- to high-energy range using a compact lightweight molybdenum/silicon multilayer mirror polarimeter (MLM). The combination of these polarization measurements with our previous total EUV cross sections has enabled us to determine experimental magnetic substate scattering angle-integrated cross sections σ0 and σ1for ML = 0, ±1, and 1 following excitation of He (1s2) 1S to HeI (1s2p) 1Po levels and ionization-excitation to He+ (2p) 2Po for electron and proton impact at a wide range velocities. The degree of linear polarization and obtained magnetic sublevel cross sections are compared to earlier theoretical calculations together with our recent 23-state R-Matrix, 1st and 2nd Born calculations. Such a detailed comparison may shed more light on the collision processes involved in positively and negatively single charge particle impact in helium. In particular it shows that electron-electron interactions play an important role in the ionization-excitation mechanism. In addition, this comprehensive database possibly will provide a deeper understanding of electron and proton induced jets in solar flare astrophysical investigations.
We present here comprehensive experimental data corresponding to helium extreme ultraviolet emission (EUV) for the 300-600A wavelength range in e- + He, H+ + He, and Hnn+ + He (n=2-3) collisions with impact velocities ranging from 1.4 to 6.9 a.u. The degree of linear polarization associated with HeI (1snp) 1Po -> (1s2) 1S decays for n-2-5 ((lambda) =510 to 584A) and HeII (2p) 2Po -> (1s) 2S transitions ((lambda) =304A), have been measured at intermediate and higher energies. These measurements have been conducted using a compact lightweight molybdenum/silicon multilayer mirror (MLM) spetropolarimeter. These experimental results are compared with our most advanced theoretical calculations using the close coupling method and several many body perturbation approaches. In this study, the degree of linear polarization will be discussed as a function of the projectile charge to elucidate few body excitation and ionization-excitation processes. Specifically, more sophisticated calculations including second Born approximation with full off-energy terms for the HeII (2p) 2Po sublevels have been used. The excellent agreement with our HeII Lyman-(alpha) data clearly demonstrates that off-energy terms in two-electron atomic interaction have very prominent effects. Our comprehensive experimental and theoretical database is also of great importance for the understanding of solar physics phenomena. Such results can be used as a new diagnostic tool for clarifying the role of electron and proton beams in solar flares.
A detailed investigation of excitation of He (1s2) 1S to He (1snp) 1P degree(s) (n equals 2 - 5) states and ionization-excitation of He (1s2) 1S to He (2p) 2P degree(s) and He (3p) 2P degree(s) states in e- + He and H+ + He collision systems is presented for a wide range of projectile velocities (2.2 a.u. < v < 6.9 a.u.). Specifically new experimental data are presented on measurements of the degree of linear polarization for excitation and excitation-ionization of He following proton impact in the extreme ultraviolet (EUV) wavelengths. These measurements have been performed using a characterized molybdenum/silicon multilayer mirror polarimeter (MLM) whose polarization characteristics have been optimized for EUV emission of He and He+. Furthermore, the proton experimental results are compared with theoretical polarization data using the first Born approximation and recent atomic orbital close coupling (AOCC) calculations for the excitation process. A comprehensive comparison of experimental data for negatively and positively charged projectiles at equal impact velocities is also given in order to elucidate differences in the collision mechanisms of two electron targets. It is important to note that these results are relevant for astrophysical diagnostics such as solar flares.
New experimental results are presented on measurements of the degree of linear polarization for ionization-excitation of He following electron and proton impact on a He gas target. These measurements have been performed using an optically characterized molybdenum/silicon (Mo/Si) multilayer mirror (MLM) polarimeter whose reflection and polarization characteristics have been optimized for the 304 angstrom wavelength region. In particular, the polarization of the photon emission from the decay of HeII (2p) 2P0 yields (1s) 2S with a wavelength of 304 Angstrom (Lyman (alpha) of HeII) has been measured for electron impact energies ranging from threshold to 1500 eV. These results are compared with polarization measurements of HeII Lyman (alpha) following proton impact on He for 187 to 460 keV beam energy corresponding to 2.7 a.u. less than v less than 4.3 a.u. projectile velocities. The integral alignment parameter A0 is also provided for negatively and positively charged particle impact to elucidate similarities and differences in the collision dynamics of two electron targets such as helium. Such results are of importance for astrophysical and laboratory plasma diagnostics.
A molybdenum/silicon (Mo/Si) multilayer mirror (MLM) polarimeter has been constructed and used to analyze the extreme ultraviolet (EUV) emission from excited HEI and HeII states following electron impact on helium for wavelengths ranging from approximately 256 angstrom to 584 angstrom. A ratio of reflectivities for s and p polarized light, Rs/Rp approximately equals 10, and a resolving power of (lambda) /(Delta) (lambda) approximately equals 6 at 304 angstrom were obtained. These characteristics and the use of a VYNS26 spectral filter were sufficient to allow a detailed polarization study of the first two members of the Lyman series of He+ at wavelengths of 304 angstrom (HeII 2p yields 1s) and 256 angstrom (HeII 3p yields 1s) for impact electron energies ranging from threshold to 1500 eV. The MLM has also been used as a single flat surface mirror polarimeter for the analysis of longer wavelength radiation (517 angstrom to 584 angstrom) from the HeI (1snp) 1Po yields (1s2) 1S series of neutral helium with Rs/Rp approximately equals 3. While MLM polarimeters have previously been used for EUV measurements with bright photon sources such as those provided by synchrotron facilities, the results from this work clearly demonstrate the feasibility of such devices with lower intensity electron and ion impact sources. The compact design of the apparatus makes it suitable as a portable measurement and calibration device.
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