Focused radiation of a Nd:YAG laser was used for ablation and production of free sample atoms from electrically conducting and nonconducting solids for analytical purposes. The microplasmas were generated in an argon buffer gas atmosphere at reduced pressure. In order to increase the intensities of analyte lines the microplasmas were reheated by a second Nd:YAG laser after the process of atomization was completed. It is demonstrated for aluminum and manganese in glass and steel samples and for magnesium and manganese in glass, copper, and aluminum that by internal standardization a common calibration curve can be obtained.

In order to find optimum conditions for laser ablation and atomization for analytical purposes, time resolved emission spectra of Nd:YAG laser-produced plasma plumes propagating into noble gas atmospheres of different pressures were measured with an optical multichannel analyzer. The time evolution of the plasma temperature was determined. Strong temperature changes were observed depending on the matrix composition. The analytical figures of merit of optical emission spectrometry (OES) of laser-produced sample plasmas were determined using, as examples, measurements of two analytes (silicon and chromium) in homogeneous and low-alloyed standard steel samples.The idea of using laser radiation for direct ablation and atomization of solid samples without going through the procedure of chemical sample preparation is already old. It came up when the first powerful laser systems became available [1] and many research groups took over the technique of laser atomization in the following years. In particular, the possibility, by tightly focussing of the laser beam, of atomizing microvolumes of the sample as in heavy ion beam sputtering, but independently of the conductivity of the sample material and the restriction of vacuum conditions above the sample surface, makes the method of laser ablation a fascinating tool. Numerous review articles were published on this topic. Without trying to rate these papers we wish to refer to only a few of the more recent ones [2][3][4][5].Despite many papers which were published on this subject (see refs.[2-5]), we have resumed the investigations of analytical applications of laser atomization which were started in our institute 20 years ago and carried out over a period of 10 years [6][7][8][9][10][11][12][13]. In the meantime there has been great progress in laser technology. Nowadays, the performance of commercial laser systems for atomization as well as of radiation detector systems is highly developed. Therefore, one may expect signifi-* To whom correspondence should be addressed t86 F. Leis et al.

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