Low pressure laser-induced breakdown spectroscopy was employed to measure mercury, strontium, and cesium under different conditions. Mercury was measured in detail to discuss the effects of pressure, laser pulse energy, delay time, and buffer gas. The continuum emission from plasma reduced dramatically to enhance signal to background ratio due to the change of influence of electron impact ionization process when reducing pressure and decreasing laser pulse energy to some extent. The comparison of mercuric chloride and mercury, as well as strontium and cesium measurements, demonstrates the enhancement of detection ability for trace species measurement using low pressure laser-induced breakdown spectroscopy
