Degenerate Four-Wave Mixing Method in Trace Isotope Analysis of Rubidium, Cesium and Potassium

The needs for isotope-level resolution in the measurement of atomic species are significant in environmental studies. By fingerprinting isotopes at sensitive levels, one can track pollutants in various environmental samples and characterize specific locations and sources including those contaminants and chemical runoff. In this work, degenerate four-wave mixing (DFWM) is employed to analyze atomic isotopes and the hyperfine structures. Rubidium (Rb), cesium (Cs) and potassium (K) isotopes are measured. The results show that isotopes and hyperfine structures of the three samples are clearly resolved. Low detect limit as 5.4 fg/ml, 0.63 pg/mL and 0.09 fg/mL are achieved for Rb, Cs and K isotopes respectively. Isotope-level resolution and trace-level sensitivity indicate that DFWM is a potential spectroscopic technique in isotope trace analysis in environment application.