LASER-ENHANCED IONIZATION OF MERCURY ATOMS IN AN INERT ATMOSPHERE WITH AVALANCHE AMPLIFICATION OF THE SIGNAL

A new method for laser-enhanced ionization detection of mercury atoms in an inert gas atmosphere is described, The method, which is based on the avalanche amplification of the signal resulting from the ionizati on from a selected Rydberg level reached by a three-step laser excitat ion of mercury vapor in a simple quartz cell, can be applied to the de termination of this element in various matrices by the use of conventi onal cold atomization techniques. The overall (collisional + photo) io nization efficiency is investigated at different temperatures, and the avalanche amplification effect is reported for Ar and P-10 gases at a tmospheric pressure. It is shown that the amplified signal is related to the number of charges produced in the laser-irradiated volume, Unde r amplifier noise-limited conditions, a detection limit of similar to 15 Hg atoms/laser pulse in the interaction region is estimated.