MERCURY VAPOR TRACE DETECTION USING PRE-EXCITATION CAVITY RING DOWN SPECTROSCOPY

摘要

Apparatus and techniques can include optically exciting an analyte gas in an optically-resonant cavity using optical energy having a first range of wavelengths including a wavelength specified to provide a metastable excited state of a species to be probed in the analyte gas. Such optical excitation can be referred to as “pre-excitation.” Optical energy having a second range of wavelengths can be coupled to the optically resonant cavity, including a wavelength specified to be absorbed using the metastable excited state of the species to be probed in the analyte gas, and outcoupled to a detector. One or more of a decay rate or a decay duration (e.g., a “ring-down” characteristic) can be monitored, such as to determine a presence or quantity of the species in the analyte gas. Such pre-excitation and probing can be referred to as Pre-Excitation Cavity Ring-Down Spectroscopy (PE-CRDS), such as for trace detection of mercury.