Optical Physics Study of Laser Interactions with Solids for Ultra-Trace Materials Analysis Using RIS. Phase 1.
Final rept. 1 Jul 86-28 Feb 87,
ATOM SCIENCES INC OAK RIDGE TN
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The feasibility of a new element analysis technique having sensitivity in the subpart per billion range was investigated. the method combines pulsed laser volatilization of a representative fraction of the sample with selective and efficient ionization of the element of interest by utilizing lasers tuned to specific transitions of the selected element. Tests on silicon and steel substrates determined cratering characteristics at incident power densities ranging from 10 to the 7th power to 2 x 10 to the 11th power Wsq cm. The quantity of material volatilized was proportional to the number of laser shots. A simple time-of-flight mass spectrometer was assembled, which together with the volatilization laser and resonance ionization laser was used to demonstrate the technique by analyzing 0.48 to 58 ppm Ga in Si samples. Sensitivity of 15 ppb was demonstrated, while the resonance ionization element selectivity was 10 to the 8th power. Guidelines were established for development of a prototype system with a 5 um analysis spot, a resonance ionization laser system for 80 elements, and a time-of-flight mass spectrometer with ablated ion rejection, thereby achieving sensitivity at the part in 10 to the 12th power. Keywords Element analysis Laser ablation Resonance ionization Semiconductor impurities Materials characteristics Sensitivity Selectivity Interference reduction Quantitation Trace studies.
- *TRACER STUDIES
- *LASER PUMPING
- *MASS SPECTROMETERS
- PULSED LASERS
- RESONANCE RADIATION
- Industrial Chemistry and Chemical Processing
- Radiation and Nuclear Chemistry