scholarly journals Radon Elimination During Benzene Preparation for Radiocarbon Dating by Liquid Scintillation Spectrometry

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 254-259 ◽  
Author(s):  
Darden Hood ◽  
Ronald Hatfield ◽  
Christopher Patrick ◽  
Jerry Stipp ◽  
Murry Tamers ◽  
...  
Keyword(s):  
Quality Control ◽  
Radiocarbon Dating ◽  
Liquid Scintillation ◽  
Liquid Scintillation Spectrometry ◽  
Spectral Analyses ◽  
Dynamic Vacuum ◽  
Low Background ◽  
Free Air ◽  
Counting Window ◽  
Age Determinations

Radon gas is a serious contaminant in radiocarbon dating by radiometry. The low specific ionizations associated with the α-particle emitting radon and its β-particle emitting daughters overlap within the 14C counting window. Elimination of radon is therefore imperative for precise 14C age determinations. This paper deals with the sources and mechanism of incorporation of radon affecting 14C dating by liquid scintillation (LS) counting, and reviews conventional radon elimination practices in 14C laboratories. It demonstrates, based on rigorous multichannel and multiparameter α- and β-particle spectral analyses of some 1000 benzene samples, that parent radium is not present and that its daughter radon is quantitatively eliminated during dynamic vacuum recovery of benzene at −78°C. However, the radon-free benzene can be recontaminated by exposure to air containing traces of radon, such as is common in concrete or low-lying laboratories. The use of radon-free air, when exposing the benzene to the atmosphere, and the monitoring of radon counts from the environment and sample benzene in a fixed ‘radon window', are essential prerequisites to the quality control of 14C age determinations in very low background systems.

scholarly journals Determination of Radon by Liquid Scintillation α/β Particle Spectrometry: Towards the Resolution of a 14C Dating Problem

Radiocarbon ◽  
1988 ◽  
Vol 30 (1) ◽  
pp. 19-24 ◽  
Author(s):  
Henry Polach ◽  
Lauri Kaihola
Keyword(s):  
Liquid Scintillation ◽  
Liquid Scintillation Spectrometry ◽  
14C Dating ◽  
Particle Emissions ◽  
Radon Decay ◽  
Mathematical Evaluation ◽  
Counting Window ◽  
Age Determinations

Traces of uranium and radium within the 14C sample generate radon (Rn) which gets occluded during the benzene synthesis, thus generating false (extra) counts within the 14C counting window. This, if undetected, gives rise to erroneous 14C age determinations. The application of simultaneous α and β liquid scintillation spectrometry will enable a mathematical evaluation of the 14C signal unaffected by α and β particle emissions from radon decay daughters.

Testing the Accuracy of 14C Age Data from Pollen Concentrates in the Yangtze Delta, China

Radiocarbon ◽  
2014 ◽  
Vol 56 (1) ◽  
pp. 181-187 ◽  
Author(s):  
Chunhai Li ◽  
Yongxiang Li ◽  
George S Burr
Keyword(s):  
Radiocarbon Dating ◽  
Liquid Scintillation ◽  
Scintillation Counting ◽  
Yangtze Delta ◽  
Plant Materials ◽  
Radiocarbon Dates ◽  
Ams Radiocarbon Dating ◽  
14C Age ◽  
Climate Events ◽  
Age Determinations

In order to test the accuracy of accelerator mass spectrometry (AMS) radiocarbon dating of pollen, 8 samples of pollen concentrates and 4 bulk organic samples were collected and analyzed from trench T1041 at the Tianluoshan site, Yuyao city, Zhejiang Province. This site was chosen because a reliable chronology had been previously established there based on radiocarbon dates of plant materials. The pollen concentrate samples were measured using AMS 14C and the 4 bulk organic samples were measured by liquid scintillation counting (LSC). The pollen concentrates and bulk organic samples yield ages that are a few hundred years to thousands of years older than those from plant materials, respectively. Contributions from reworked sediments can explain the older ages for the pollen concentrates and sediment organic dates. This study suggests that caution must be exercised when discussing millennial- or centennial-scale climate events based on chronologies that are controlled by age determinations of pollen concentrates.

Improved Results Using Higher Ratios of Scintillator Solution to Benzene in Liquid Scintillation Spectrometry

Radiocarbon ◽  
2000 ◽  
Vol 42 (2) ◽  
pp. 295-303
Author(s):  
Motoharu Koba
Keyword(s):  
Radiocarbon Dating ◽  
Figure Of Merit ◽  
Liquid Scintillation ◽  
Weight Ratio ◽  
Liquid Scintillation Spectrometry ◽  
Standard Spectrum ◽  
External Standard

Practical effects of the volumetric or weight ratio of scintillator solution to sample benzene in liquid scintillation spectrometry were examined here for radiocarbon dating. It is concluded, using a LKB-Wallac Quantulus™ 1220 and Teflon™-copper 3 mL vials with scintillator of toluene-based PPO and POPOP, that solutions containing the same concentrations of the same ratio, 1.3 or more, of scintillator solution to sample benzene show the same cpm/g and the same channel value of external standard spectrum, irrespective of different gross volumes of solutions. The addition of scintillator solution reduces background in 0.5 mL or so of benzene, and results in an appreciably enlarged figure of merit.

scholarly journals Cosmic Background Reduction in the Radiocarbon Measurements by Liquid Scintillation Spectrometry at the Underground Laboratory of Gran Sasso

Radiocarbon ◽  
2001 ◽  
Vol 43 (2A) ◽  
pp. 157-161 ◽  
Author(s):  
Wolfango Plastino ◽  
Lauri Kaihola ◽  
Paolo Bartolomei ◽  
Francesco Bella
Keyword(s):  
Noise Reduction ◽  
High Precision ◽  
Liquid Scintillation ◽  
Center Of Gravity ◽  
Underground Laboratory ◽  
Liquid Scintillation Spectrometry ◽  
Low Background ◽  
Background Reduction ◽  
Cosmic Background ◽  
Cosmic Noise

Radiocarbon measurements by two 1220 Quantulus™ ultra low background liquid scintillation spectrometers were performed at the underground laboratory of Gran Sasso and the Radiocarbon Laboratory of E.N.E.A.-Bologna to study the efficiency and background variations related to measurement sites. The same configuration setup, i.e. the same center of gravity of the 14C spectrum (SQP(I) = 410 ± 1) was obtained in both instruments. Many different background and modern standards with pure analytical benzene were used and spectra for 40 one-hour periods were obtained. The data indicates a background reduction of approximately 65% between the surface and underground laboratories, with no differences in the efficiency. Recording similar efficiencies in both spectrometers is probably due to fairly identical photomultiplier characteristics. The cosmic noise reduction observed at the laboratory of Gran Sasso makes it possible to perform high precision 14C measurements and to extend for these idealized samples the present maximum dating limit from 58,000 BP to 62,000 BP (5 mL, 3 days counting).

scholarly journals Precise 14C Measurement By Liquid Scintillation Counting

Radiocarbon ◽  
1979 ◽  
Vol 21 (1) ◽  
pp. 1-21 ◽  
Author(s):  
Gordon W Pearson
Keyword(s):  
Liquid Scintillation Counting ◽  
Count Rate ◽  
Radiocarbon Dating ◽  
Liquid Scintillation ◽  
Scintillation Counting ◽  
Reference Standard ◽  
Standard Material ◽  
Image Position

Radiocarbon dating involves a comparison of the count rate of sample carbon with that of modern reference standard material. To calculate a date the ratio Z must be determined where

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