Photoresonant plasma as a new tool for LIBS

A plasma created by the action of a high-intensity resonant laser radiation on a vapor or a gas (Photoresonant Plasma, PRP) is considered as a version of the Laser Induced Breakdown Spectroscopy (LIBS). The physical mechanisms determining the transformation of the resonant laser radiation energy into that of a plasma are analyzed. It is shown that the transformation of resonant radiation proceeds much more quickly in comparison with the conventional off-resonant irradiation. This is one of the main advantages of use of PRP in LIBS technique. There have been stated the interrelation between the quasi-stationary plasma temperature established after termination of the laser pulse and the concentration of the admixture vapor to be determined. This interrelation can be used as the basis for LIBS determination of the elemental content of the irradiated surface. The set of equations determining the time evolution of PRP is formulated. The quasi-stationary parameters of alkali metal PRP after terminating the laser irradiation and also during the irradiation have been evaluated on the basis of the analysis of these equations.