Inhaltszusammenfassung

Laser-induced breakdown spectroscopy (LIBS) is widely used to determine the elemental composition of samples. Usually, the emission of single atoms and ions is determined in order to examine the composition of a sample. However, there are several elements exhibiting very weak emission lines in LIBS measurements (e.g. halogens). During the cool-down process of the laser induced plasma usually the evaporated atoms form several radicals and molecules (some of these exist just a short time befor...Laser-induced breakdown spectroscopy (LIBS) is widely used to determine the elemental composition of samples. Usually, the emission of single atoms and ions is determined in order to examine the composition of a sample. However, there are several elements exhibiting very weak emission lines in LIBS measurements (e.g. halogens). During the cool-down process of the laser induced plasma usually the evaporated atoms form several radicals and molecules (some of these exist just a short time before reacting further). In some cases the radicals or molecules of these elements have stronger emission lines then the elements forming the radicals or molecules. This may lead to lower detection limits. In order to study the formation process of radicals and molecules we performed both experimental examinations and simulation calculations. We studied the generation of several diatomic radicals consisting of cations Ca2+ and Al3+, and anions like F−, Cl−, and O2−. The used laser pulses had a pulse duration in the range from µs to fs, and a pulse energy in the range of several µJ to several 100 mJ. As an application, we measured the diffusion of chloride (e.g. from de-icing salt) in concrete. Quantitative measurement of chloride is of high industrial interest because it allows the estimation of the critical pitting corrosion process and thus the expected lifetime of a concrete structure. In the laser-induced plasma plume chlorine and calcium from the cement react to CaCl radicals with strong molecular emission bands in the visible spectral range, from which the concentration of chloride can be deduced.» weiterlesen» einklappen

Autoren

Klassifikation

DFG Fachgebiet:
Optik, Quantenoptik und Physik der Atome, Moleküle und Plasmen

DDC Sachgruppe:
Physik