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.

Metastable superheated and supercooled vortex states in NbSe2 crystals were probed with fast transport measurements over a wide range of field and temperature. The limit of metastability of the superheated vortex lattice defines a line in the phase diagram that lies below the superconducting transition and is clearly separated from it. This line is identified as the vortex lattice spinodal, and is in good agreement with recent theoretical predictions by Li and Rosenstein [Phys. Rev. B 65, 220504 (2002)]; cond-mat/0305258]. By contrast, no limit of metastability is observed for the supercooled disordered state.

A new ultra sensitive laser-based analytical technique, intracavity optogalvanic spectroscopy (ICOGS), allowing extremely high sensitivity for detection of 14 C-labeled carbon dioxide has recently been demonstrated. Capable of replacing accelerator mass spectrometers (AMS) for many applications, the technique quantifies zeptomoles of 14 C in sub micromole CO 2 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 have been obtained with theoretical limits much lower. Using a 15 W 14 CO 2 laser, a linear calibration with samples from 5 × 10 −15 to >1.5 × 10 −12 in 14 C/ 12 C ratios, as determined by AMS, was demonstrated. Calibration becomes non linear over larger concentration ranges due to interactions between CO 2 and buffer gas, laser saturation effects and changes in equilibration time constants. The instrument is small (table top), low maintenance and can be coupled to GC or LC input. The method can also be applied to detection of other trace entities. Possible applications include microdosing studies in drug development, individualized sub therapeutic tests of drug metabolism, carbon dating and real time monitoring of atmospheric radiocarbon.

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