Picosecond pump-probe absorption spectroscopy is a spatially resolved technique that is capable of measuring species concentrations in an absolute sense without the need for calibrations. When laser pulses are used that are shorter than the collision time in a sample, this pump-probe technique exhibits reduced sensitivity to collisional effects such as electronic quenching. We describe modeling and experimental characterization of this technique. The model is developed from rate equations that describe the interactions of the pump and probe pulses with the sample. Calculations based on the density-matrix equations are used to identify limits of applicability for the model. Excellent agreement between the model and the experimental data is observed when both 1.3- and 65-ps pulses are used to detect potassium in a flame and in an atomic vapor cell.
© 2002 Optical Society of America
Thomas B. Settersten and Mark A. Linne, "Picosecond Pump-Probe Absorption Spectroscopy in Gases: Models and Experimental Validation," Appl. Opt. 41, 2869-2878 (2002)