ИСТИНА

The use of emission of diatomic molecules instead of atomic lines to determine hardly excited species like halogens is well-known approach in atomic emission spectroscopy. The advantages of the molecular bands are related to a sufficiently high excitation potential chlorine line (~ 10.5 eV), and a low degree of its atomization in plume. The molecular bands of MgCl, CaCl and AlCl were evaluated for chlorine detection. We have also applied double-pulse LIBS to use the atomic lines Cl I 833.7 nm for the comparison. It was found that only the orange system of CaCl molecule was sufficiently intense for chlorine determination in concrete by common LIBS at the late times of plasma existence (30 µs after laser pulse). The application of PCR provided a calibration model appropriate for reliable chlorine determination at the threshold level. Thus the multivariate calibration with the use of CaCl emission measured with the common LIBS setup as analytical signal improved the sensitivity.