Sample damage

The conclusion is that, because sample damage cannot be fully ruled out. quotation of a damage index as defined above may improve significantly the traceable quality of analytical data. The requirements of the ASTM standard practice E1015-90 [11] could be met in this way. 

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Depth of analysis Lateral resolution Imaging Sample damage Main uses... 

ERS is still being developed, refined, and enhanced to improve its depth resolution and absolute precision, to facilitate data reducdon and to minimize sample damage. Excellent results can be achieved simply by implementing ERS with careful regard for the issues described in this article. 

There is a number of alternative Raman imaging techniques these include using the Hadamard transform technique [25-27], and such as fibre-bundle image compression, which however is not yet commercially available [26-31]. However in the latter approach, the laser power on the sample could be high, since the beam is not defocused, and the possibility of sample damage increases. 

This paper explores the trade-offs of gem damage during LIBS analysis and data quality under a variety of analytical conditions. Two lasers, a Big Sky Laser Technology (now Quantel USA) Nd-YAG nano-second laser operated at its fundamental wavelength of 1064 nm, and a Raydiance, Inc., pico-second laser operated at its fundamental wavelength of 1552 nm as well as harmonics at 776, 517.2, and 388 nm, are used in separate LIBS systems. Furthermore, the use of inert gas environment (He or Ar) is explored to increase peak intensities at lower laser power and sample damage. 

The FAB matrix is essentially a nonvolatile liquid material, such as those illustrated in Scheme 1, that serves to constantly replenish the surface with new sample as the incident ion beam bombards the surface. The matrix also serves to minimize sample damage from the high-energy particle beam by absorbing most of the incident energy and is believed to facilitate the ionization process. The spectrum produced often includes matrix peaks along with some fragments and a peak for the protonated or cationized (i.e., M + Na+) molecular ion. 

Among the main difficulties with electron crystallography are (1) sample damage from the electron beam (a 0.1-A wave carries a lot of energy), (2) low contrast between the solvent and the object under study, and (3) weak diffraction from the necessarily very thin arrays that can be studied by this method. Despite these obstacles, cryoscopic methods (Chapter 3, Section V) and image processing techniques have made electron crystallography a powerful probe of macromolecular structure, especially for membrane proteins, many of which resist crystallization. 

In UV-resonance Raman (UVRR) studies, UV lines such as the fourth harmonic (266 nm) of the Nd YAG laser are used for excitation. Under prolonged illumination by focused UV radiation, quartz and other UV-transparent materials tend to become fluorescent. To avoid the use of window materials and to minimize sample damage by strong UV light, several sampling techniques, such as the fluid jet stream technique (60) and the thin-film technique (61), have been developed. 

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