TitleIntracavity optogalvanic spectroscopy for radiocarbon analysis with attomole sensitivity
NameIlkmen, Erhan (author), Murnick, Daniel (chair), Wu, Zhen (internal member), Schaden, Martin (internal member), Hall, Gene (internal member), Barat, Robert (internal member), Rutgers University, Graduate School - Newark,
DescriptionCarbon-14 (radiocarbon) is a naturally occurring radioactive isotope of carbon, having an extremely low natural abundance in living organisms (14C/C ~ 10-12) and a long half life of ~ 5730 years. These properties make it an ideal organic tracer for various applications
in biological, pharmaceutical and environmental sciences as well as carbon dating. Today, the state of the art radiocarbon quantitation technique is Accelerator Mass Spectrometry (AMS) which is based on ion counting using a several megavolt tandem electrostatic accelerator as a mass spectrometer. Although AMS sets the standard for high sensitivity detection, its size, cost and complexity as an analysis system, limits its wide and routine use especially in laboratory or field applications. In this thesis, a new ultrasensitive
laser based analytical technique that can quantify attomoles of 14C in submicrogram samples is demonstrated. The new system exhibits similar or better
measurement capabilities as AMS, in sensitivity (14C/C ≤ 10-15), precision (≤3%) and accuracy (≤5%). Additional advantages include non destructive analysis capability, small size, being a table top instrument, high sample throughput capability via flow processing
and the potential to be coupled to GC/LC instrumentation.
The developed Intracavity Optogalvanic Spectroscopy (ICOGS) system is based on measuring changes in electrical properties of a weakly ionized glow discharge placed inside the cavity of a periodically modulated high power (50 W) 14CO2 laser. This new configuration enabled improvement of the signal detection sensitivity by about six orders of magnitude compared to the conventional external cell optogalvanic spectroscopy
method. The signal enhancement mechanism is similar to, but with key differences from the well studied optical detection method Intracavity Absorption Spectroscopy (ICAS). Measurement capability of this new system is demonstrated with calibration curves
relative to AMS measurements with a dynamic range of more than five orders of magnitude. The systems studied exhibited saturation effects with laser power and
measurement time and also non-linearities in response with samples having enrichments greater than 12 Modern. (1 Modern = 1.10-12 14C/12C ratio.) However, standard operating procedures were developed for accurately measuring unknown samples. For a more thorough quantitative understanding of the enhancement mechanism, a physical rate equations model has been outlined.
NoteIncludes bibliographical references (p. 88-93)
Noteby Erhan Ilkmen
CollectionGraduate School - Newark Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.