The avalanche amplification of the laser-enhanced ionization signal of Cs atoms in a flame has been studied. Ionization of Cs atoms, enhanced by two-step excitation, was detected in hydrogen and propane flames. By employing the effect of avalanche amplification of electrons, high signal-to-noise ratio (approximately 10(4)) was obtained for a 100 ppt Cs solution. The extrapolated limit of detection was 30 fg/mL (ppq).

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The recently developed mercury resonance ionization imaging detector (RIID) has many potential applications in the field of imaging science. We have demonstrated that useful information can be obtained from the time-resolved ionization signal detected along with the image of the object. Clearly distinguishable time-resolved signals from resonance ionization of mercury atoms and photoelectrons created within the channels of a microchannel plate by a UV signal transition of Hg at 253.7 nm were observed. Also, a new source of noise has been identified as low-mass ion desorption by 253.7 nm radiation from the inner parts of the Hg RIID. The time-resolved signal detection allowed temporal correction for the additional noises caused by nonresonant ionization processes inside the RIID, such as photoelectric effect and low-mass ion desorption. The temporal resolution of the RIID could be used for frequency shifted radiation detection and imaging.

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