We show a new ultrasensitive laser-based analytical technique, intracavity optogalvanic spectroscopy, allowing extremely high sensitivity for detection of (14)C-labeled carbon dioxide. Capable of replacing large accelerator mass spectrometers, the technique quantifies attomoles of (14)C in submicrogram samples. Based on the specificity of narrow laser resonances coupled with the sensitivity provided by standing waves in an optical cavity and detection via impedance variations, limits of detection near 10(-15) (14)C/(12)C ratios are obtained. Using a 15-W (14)CO2 laser, a linear calibration with samples from 10(-15) to >1.5 x 10(-12) in (14)C/(12)C ratios, as determined by accelerator mass spectrometry, is demonstrated. Possible applications include microdosing studies in drug development, individualized subtherapeutic tests of drug metabolism, carbon dating and real time monitoring of atmospheric radiocarbon. The method can also be applied to detection of other trace entities.

A dc electron beam at 20 keV is used for the excitation of pure rare gases at pressures up to 1.7 bar. The well known second excimer continua of argon, krypton, and xenon observed under these excitation conditions provide an efficient light source in the vacuum ultraviolet spectral region between 120 and 200 nm. Thin (300 nm) SiNx foils are used as entrance windows for the low energy electron beam. Due to the flexibility of the production process of the thin foils one can consider various shapes and sizes of the light emitting region to be manufactured. Efficiencies of ∼30% are observed for the conversion of electron beam energy into light.

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The effects of frequency variation in a high-frequency ). low-pressure (250mTorr), capacitively coupled argon discharge have been investigated. Spatially resolved optical emission and RF voltage and current measurements are reported. Results of fluid model simulations are also presented to aid in the interpretation of the experiments. Scaling of piasma parameters is studied under three conditions: constant frequency, constant applied voltage and constant current. The scaling laws derived here suggest ways to optimize a very high-frequency plasma reactor for thin film etching and deposition applications.

A laser technique for analysis of carbon-13:carbon-12 ratios with the specificity of laser resonance spectroscopy and the sensitivity and accuracy typical of isotope ratio mass spectrometers is reported. The technique is based on laser optogalvanic effect spectroscopy, in which an electrical (galvanic) signal is detected in response to the optical stimulation of a resonance transition in a gas discharge species. Carbon dioxide molecular gas lasers are used, with the probed transitions being identical to the lasing transitions. Measurements for carbon dioxide samples with 100-second averaging times yield isotopic ratios with a precision of better than 10 parts per million.