The Radiocarbon Intracavity Optogalvanic Spectroscopy Setup at Uppsala

Abstract

ABSTRACT. Accelerator Mass Spectrometry (AMS) is by far the predominant technology deployed for radiocarbon tracer studies. Applications are widespread from archaeology to biological, environmental, and pharmaceutical sciences. In spite of its excellent performance AMS is expensive and complicated to operate. Consequently, alternative detection techniques for radiocarbon are of great interest, with the vision of a compact, user-friendly and inexpensive analytical method. Here we report on the use of intra-cavity optogalvanic spectroscopy (ICOGS) for measurements of the 14 C/ 12 C ratio. This new detection technique was developed by Murnick and co-workers (Murnick et al. 2008). In the infra-red (IR) region, CO 2 molecules have strong absorption coefficients. The IR-absorption lines are narrow in linewidth and shifted for different carbon isotopes. These properties can potentially be exploited to detect 14 CO 2 , 13 CO 2 or 12 CO 2 molecules unambiguously. In ICOGS, the sample is introduced as CO 2 gas, eliminating the graphitization step which is required in most AMS labs. In this paper, the status of the ICOGS setup in Uppsala is presented. The system is operational but not yet fully developed. Data are presented for initial results which illustrate the dependence of the optogalvanic signal on various parameters, such as background and plasma induced changes in the sample gas composition.

Evaluation of Intracavity Optogalvanic Spectroscopy for Radiocarbon Measurements

“…We have not been able to reproduce the reported results concerning the OG signals dependence on 14 C concentration and wavelength, and, ultimately, not seen any evidence of the capability of ICOGS to unambiguously detect 14 C at all. Instead, we have found indications that the reported results can be products of measurement uncertainties and mistakes.…”

“…Employing AMS for analysis of samples of blood, urine, breath, tissue, biopsies etc., looking for the C 14 labeled molecules and their metabolites, the distribution, absorption and elimination of the drug in the body can be studied.…”

“…MATERIALS AND METHODS. The experimental setup in our laboratory has been thoroughly described in a previous publication 14 . The schematic of the setup is described in Figure 1.…”

Comment on “Intracavity OptoGalvanic Spectroscopy Not Suitable for Ambient Level Radiocarbon Detection”

“…In spite of extensive efforts at the following five sites around the world, the original data still remains unconfirmed: 1) Murnick's group at Rutgers University, 2) Professor Meijer's group at the Energy and Sustainability Research Institute Groningen at University of Groningen, 3) Professor Lackner's group at the Department of Earth and Environmental Engineering at Columbia University, 4) our group at the Department of Physics and Astronomy at Uppsala University, and 5) the company Planetary Emission Management Inc., Beltsville, MD, USA. On the contrary, a number of publications have seriously questioned the scientific validity of the original report [2][3][4][5][6] .…”

“…Most importantly, it fills a void in the aggregated literature on ICOGS [1][2][3][4][5][6] , namely the study of highly enriched 14 CO 2 samples. Hence, it is an important contribution to the field, and well worthy of publication in Analytical Chemistry.…”