Photoabsorption of Positive Ions
The dual laser produced plasma (DLP) technique has been applied very successfully to the generation of photoabsorption spectra of ions, atoms and corrosive species such as halogens.1-5 In this method, one high power laser pulse, usually from a Q-switched laser, is used to produce a plasma of the ions of interest while a second pulse is tightly focused onto a heavy lanthanide (Z≥62) or tungsten target to provide an intense soft X-ray/EUV backlighting continuum. If the target used is samarium, the continuum is line free from 30-2,000Å.6 By varying the interpulse time delay, changing the pulse power density or probing different plasma regions, absorption from different ion stages may be obtained. Currently both photographic and photoelectronic detection is used; the former gives excellent energy resolution (ΔE/E≈l04-105) but at the expense of very poor intensity information, while the latter has medium energy resolution (ΔE/E≈103-104) and limited energy coverage but possesses linear intensity response and good dynamic range. Photographic plates are thus most suitable for investigating sharp features and spectra which span an extensive energy range while photoelectric detection is preferred for the investigation broad resonance features and autoionizing line profiles. However it should be pointed out that plasma broadening effects (Δλ∼0.05Å) are such that the resolution available photographically is rarely exploited in recording ion spectra.
KeywordsGiant Dipole Resonance High Power Laser Pulse Photoelectric Detection Plasma Electron Temperature Photoabsorption Spectrum
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