Pulsed GD source

Although the coupling of steady-state discharges to the TOF-MS has proved successful, the TOF-MS is perhaps better suited for the investigation of pulsed GD sources. Here, the high temporal resolution and multielement capabilities of the TOF-MS can be fully exploited, with the coupling of a pulsed source to a pulsed... 

One application of great interest is depth profiling by means of GD-TOF-MS. Particularly in conjunction with pulsed GD sources, the simultaneous multi-elemental capabilities of TOF-MS permit the analysis of solid samples as a function of depth (or time) as the discharge operates. In such a case, one might envision complete trace elemental analysis of solid materials with resolution on the nanometer scale. 

Sputtering rates and penetration rates In order not to elaborate excessively on these concepts, this section deals only with the theoretical aspects in relation to pulsed GD sources. Interested readers are referred to the original references for more details. 

A modified version of the Grimm-type GDL has been described by Shao and Horlich [594], The source has a floating restrictor and is designed so as to replace an ICP torch in an ICP-MS. Therefore, the anode is slightly positive with respect to the earthed skimmer interface of the MS system. The simultaneous analysis of an unknown sample and a reference material was carried out by means of a system based on two pulsed GD sources housed within the same tube [595], Optimization of the relative position of the two cathodes was achieved by evaluating the signals produced in GD-MS when using the same specimen for each of them. 

A Gd + doped crystal is illuminated with a pulsed light source, so that the l7/2 excited state of this ion is populated by absorbing 1 mJ of energy per incident pulse. Determine the heat delivered to the crystal per excitation pulse if the nonradiative rate from this state is 10 s The fluorescence lifetime of the l7/2 state is 30 /xs. 

A tandem system consisting of pulsed dye laser ablation and ionization in a GD source for MS have been described by Barshick and Harrison [649]. The role played by the working gas (Ar, He, Ne) on redeposition of sputtered material has also been clarified. Removal of interfering species in GD-MS is possible through the use of getters such as Ag, C, Ta, Ti and W [650]. This approach has been applied successfully in the determination of rare earths so as to avoid oxide ion formation. 

In conclusion, GD-OE S is a very versatile analytical technique which is still in a state of rapid technical development. In particular, the introduction of rf sources for non-conductive materials has opened up new areas of application. Further development of more advanced techniques, e. g. pulsed glow discharge operation combined with time-gated detection [4.217], is likely to improve the analytical capabilities of GD-OE S in the near future. 

Work by Charrier et al. (1999) was carried out at the ISIS pulsed source and thus suffered more severely from losses of asymmetry in the initial dead time. The resiJts for the Gd and Tb compoimds are quite comparable to those of Noakes et al. (1998) when this limitation is taken into accoimt In particular, the (unexplained) two-signal spectra (rapidly and slowly relaxing) are observed as well. The study also includes measurements on the Dy and Y compounds. The former behaves much like the Tb quasicrystal, as expected. The Y material is nonmagnetic and muon spin depolarization arises solely from nuclear dipole moments. The fact that no sudden change in the rather weak depolarization rate ( 0.01 p,s ) was seen between 300 K and 10K makes muon diffusion unlikely in this structure. 

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