Gif Natural Radiocarbon Measurements VII

Abstract

C 14 dates reported below were obtained mainly at the end of 1968 and during 1969 on archaeologic and geologic samples. Techniques of measurement used are unchanged. Since 1968, 4 complete routine sets have been running, each equipped with a 1 L CO 2 proportional counter. One is made of stainless steel with a background of 2.70 cpm at pressure 1 atm and the others are of OFHC copper with a background of either 1.10 or 1.30 cpm for a corresponding pressure of, respectively, 1 or 2 atm. For age calculation, 95% activity of NBS oxalic acid is used as the modern standard and the value of 5570 ± 30 years is used for the half-life of C 14 . Dates are expressed in years b.p. (before a.d. 1950).