RESUMEN
It is demonstrated that the optogalvanic effect in a sodium hollow cathode discharge is a sensitive detector specific to the intracavity absorption of sodium atoms in a flame. In this feasibility study the variation of the optogalvanic signal vs the sodium concentration in the flame indicated a detection limit below 1 ng/ml. The sensitivity can be easily improved, and this technique is applicable to other atoms and Doppler-free intermodulation spectroscopic detection methods.
RESUMEN
Several atomic emission sources were investigated for their potential to induce optogalvanic signals in hollow cathode lamps. The sources included an inductively coupled argon plasma, a H(2)-O(2) flame, a high-temperature furnace, electrodeless microwave discharge lamps, and hollow cathode lamps. Successful results were obtained with argon emission from the inductively coupled plasma focused into an argon-filled hollow cathode tube and with atomic emission from one hollow cathode discharge focused into a hollow cathode tube containing the same element. Very low level optogalvanic signals were observed from the other sources but could not be unambiguously ascribed to emission from a specific element. A problem encountered was the presence of a background signal due to photoelectric emission and possibly radiative heating of the cathode.