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If we give the label "old carbon" to ancient carbon sources with no recent interactive contact with the air (e.g., long-buried carbon such as in coal that has no exposure to radioactivity), then old carbon contamination could cause samples to date older, but it would have to be a great deal of contamination.For example, a 5,000 year-old sample would require contamination larger than the sample itself to make it date to 50,000 years old. Marina Chicurel - Can Organisms Speed Their Own Evolution? : A Christian Biologist's In-Depth Look at the Evidence Reveals a Surprising Harmony Between Science and God (3.6MB)Bob Altemeyer - The Authoritarians (1.32 MB)National Academy of Science - Science, Evolution, and Creationism (3.16 MB)John Woodmorappe - Radiometric Geochronology Reappraised (3.35MB)Defining Reasonableness Online: A Case Study of an Internet Forumabout the Creation / Evolution Controversy John A Davison - A Prescribed Evolutionary Hypothesis Charlie Rose Show - Discussion About Charles Darwin (w/ EO Wilson & James Watson)New Scientist - Are We Still Evolving?So the potential error in measurement of an actual sample would be /-0.05% of the i4C/i3C ratio for the modern reference standard.Seeing as this measurement of age is based on exponential decay this does not result in a major error in ages Hi Philo Nibbler, I'll start with simple answers and more details can be filled in as necessary.This machine background is equivalent to an age of about 61000 years. With the ion source containing an empty aluminum target holder open to the beam transport system, a C value obtained at LLNL on natural graphite used by the UCR radiocarbon laboratory to monitor contamination from loading graphite into their target holders is 64,460 3200 BP (CAMS-12338; 64,500 1800 BP and CAMS-12339; 58,800 1000 BP).Now I read this as saying that they ran the test without a sample and measured an age of 61000 yrs age. The average (N=7) My only question here is what is meant by "with the ion source closed off from the remainder of the beam line, ≥104 ka (0 counts in 20.5 min of counting).
Keep in mind that they were working more than 30 years ago with the technology available in 1984.
The reason this background measurement is unlikely to stem from "stray carbon molecules" is because those carbon molecules would most likely be carbon dioxide from the air.
The carbon in the air is constantly replenished with My only question here is what is meant by "with the ion source closed off from the remainder of the beam line, ≥104 ka (0 counts in 20.5 min of counting).
When no sample carbon is present (either an emptyholder or a bare tantalum wire) a beam current of l-5 n A is generated, with a 14C count rate less than 10% of that from the best dead sample. SOUTHON3 "REDUCTION IN BACKGROUNDS OF MICROSAMPLES FOR AMS 14C DATING"AMS 14C measurements were done at the Center for Accelerator Mass Spectrometry (CAMS), University of California Lawrence Livermore National Laboratory (LLNL) (Davis et a1.1990; Southon et a1.1990; 1992).
The lowest 14C/13C ratio we have measured is for geological graphite, whichyields lo-15 PA of beam current at less than 0.05% of the i4C/i3C ratio for the modern reference standard. Experiments carried out with the CAMS FN tandem accelerator using a GIC Model 846 ion source determined that the machine background as defined by Schmidt, Balsley and Leach (1987), i.e., with the ion source closed off from the remainder of the beam line, ≥104 ka (0 counts in 20.5 min of counting).
After searching the internet for the last couple of days and reading several freely available scholarly articles I have failed to find specific information explaining some things I'm curious about.