4
Carbon-14
Martine Paterne, Élisabeth Michel,
and Christine Hatté et Jean-Claude Dutay
Seventy years after its discovery by W.B.F. Libby and collaborators (Arnold and Libby 1949; Libby 1952), the
radiocarbon (
14 C) method of dating is still of great interest in
many scientific fields in biology, earth science, climate,
environment and archeology. Libby received the Nobel Prize
in Chemistry in 1960 and the chairman of the Nobel Committee highlighted the importance of this discovery in these
terms: “Seldom has a single discovery in chemistry had such
an impact on the thinking of so many fields of human
endeavor. Seldom has a single discovery generated such
wide public interest”. The history of the
14 C method is an
excellent example of the fruitful exchanges among different
scientific fields and of the complementarity between scientific advances and technological innovations. Since its discovery, more than a hundred and fifty laboratories in the
world are now dedicated to
14 C dating. In the 1980s, new
technologies, notably the accelerator mass spectrometry,
allowed the use of samples of increasingly reduced sizes and
a better precision of the
14 C ages. Now, the physical and
chemical processes involved in biological and environmental
changes may be analyzed at the molecular scale.
The method and techniques of
14 C dating have been the
subject of several web and journal publications to which
readers may refer (Libby 1981; Taylor 1987; Taylor et al.
1992; Currie 2004).
Principles of the Radiocarbon Method
Discovery of the Method
Kamen (1963) reported the history of the
14 C discovery and
Libby’s meeting with
14 C in 1939 at Berkeley. He attributed
the physical prediction of the existence of this isotope to the
physicist Kurie (Kamen 1963), who studied neutron-induced
disintegration of light elements such as nitrogen (
14 N).
During these experiments, Kurie observed infrequent and
abnormal long thin traces in a cloud chamber filled with air.
He attributed them to the emission of protons following the
reaction
14 N (n,
1 H)
14 C although other reactions such as
14
N
(n,
2 H)
12 C and
14 N (n,
3 H)
12 C could also have been possible. In 1936, Burcham and Goldhaber demonstrated that no
a-particles were emitted in the slow neutron disintegration of
14 N and only the reaction
14 N(n,
1 H)
14 C was possible with
proton emission and formation of
14 C noted
14 N(n, p)
14 C
(Kamen 1963).
The evidence of the chemical existence of
14 C is due to
Ruben, a chemist and Libby’s student, and to Kamen, a
radiochemist of the Lawrence Livermore Radiation Laboratory at Berkeley. They investigated the assimilation processes of CO 2 during photosynthesis by incubating plant
species with the radioactive isotope
11 C, which was produced in the Livermore cyclotron (Ruben et al. 1949).
Labeled intermediate solutions were deposited on a blotting
paper, and, once dried, the paper was protected by a plastic
film and wrapped inside a screen-wall counter. The use of
11 C in biology was however very difficult due to long separation phases of various photosynthetic pigments by ultracentrifugation and a half-life of 21 min. Furthermore, it was
not very competitive with the
13 C labeling of plants. At the
request of Lawrence, who invented the cyclotron and
received the Nobel Prize in Physics in 1939, the existence or
not of long-lived radioactive isotopes was systematically
sought for each element of the first column of the periodic
table (H, C, N, O), and thus the search for the chemical
existence of
14 C (Kamen 1963). Kamen submitted a graphite
target to a deuteron beam in the cyclotron overnight. After
burning the graphite, Ruben precipitated the CO 2 into a
carbonate. This precipitate was furnished to their colleague
in the chemistry department, W.F. Libby, who developed
proportional counters to measure the radioactivity of elements such as neodymium, samarium, rubidium and lutetium, to determine their period (Libby 1934). The detection
M. Paterne (&) Á É. Michel Á C. H. et Jean-Claude Dutay
Laboratoire des Sciences du Climat et de l’Environnement,
LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay,
91190 Gif-sur-Yvette, France
e-mail: martine.paterne@lsce.ipsl.fr
© Springer Nature Switzerland AG 2021
G. Ramstein et al. (eds.), Paleoclimatology, Frontiers in Earth Sciences,
https://doi.org/10.1007/978-3-030-24982-3_4
51
Carbon-14
Martine Paterne, Élisabeth Michel,
and Christine Hatté et Jean-Claude Dutay
Seventy years after its discovery by W.B.F. Libby and collaborators (Arnold and Libby 1949; Libby 1952), the
radiocarbon (
14 C) method of dating is still of great interest in
many scientific fields in biology, earth science, climate,
environment and archeology. Libby received the Nobel Prize
in Chemistry in 1960 and the chairman of the Nobel Committee highlighted the importance of this discovery in these
terms: “Seldom has a single discovery in chemistry had such
an impact on the thinking of so many fields of human
endeavor. Seldom has a single discovery generated such
wide public interest”. The history of the
14 C method is an
excellent example of the fruitful exchanges among different
scientific fields and of the complementarity between scientific advances and technological innovations. Since its discovery, more than a hundred and fifty laboratories in the
world are now dedicated to
14 C dating. In the 1980s, new
technologies, notably the accelerator mass spectrometry,
allowed the use of samples of increasingly reduced sizes and
a better precision of the
14 C ages. Now, the physical and
chemical processes involved in biological and environmental
changes may be analyzed at the molecular scale.
The method and techniques of
14 C dating have been the
subject of several web and journal publications to which
readers may refer (Libby 1981; Taylor 1987; Taylor et al.
1992; Currie 2004).
Principles of the Radiocarbon Method
Discovery of the Method
Kamen (1963) reported the history of the
14 C discovery and
Libby’s meeting with
14 C in 1939 at Berkeley. He attributed
the physical prediction of the existence of this isotope to the
physicist Kurie (Kamen 1963), who studied neutron-induced
disintegration of light elements such as nitrogen (
14 N).
During these experiments, Kurie observed infrequent and
abnormal long thin traces in a cloud chamber filled with air.
He attributed them to the emission of protons following the
reaction
14 N (n,
1 H)
14 C although other reactions such as
14
N
(n,
2 H)
12 C and
14 N (n,
3 H)
12 C could also have been possible. In 1936, Burcham and Goldhaber demonstrated that no
a-particles were emitted in the slow neutron disintegration of
14 N and only the reaction
14 N(n,
1 H)
14 C was possible with
proton emission and formation of
14 C noted
14 N(n, p)
14 C
(Kamen 1963).
The evidence of the chemical existence of
14 C is due to
Ruben, a chemist and Libby’s student, and to Kamen, a
radiochemist of the Lawrence Livermore Radiation Laboratory at Berkeley. They investigated the assimilation processes of CO 2 during photosynthesis by incubating plant
species with the radioactive isotope
11 C, which was produced in the Livermore cyclotron (Ruben et al. 1949).
Labeled intermediate solutions were deposited on a blotting
paper, and, once dried, the paper was protected by a plastic
film and wrapped inside a screen-wall counter. The use of
11 C in biology was however very difficult due to long separation phases of various photosynthetic pigments by ultracentrifugation and a half-life of 21 min. Furthermore, it was
not very competitive with the
13 C labeling of plants. At the
request of Lawrence, who invented the cyclotron and
received the Nobel Prize in Physics in 1939, the existence or
not of long-lived radioactive isotopes was systematically
sought for each element of the first column of the periodic
table (H, C, N, O), and thus the search for the chemical
existence of
14 C (Kamen 1963). Kamen submitted a graphite
target to a deuteron beam in the cyclotron overnight. After
burning the graphite, Ruben precipitated the CO 2 into a
carbonate. This precipitate was furnished to their colleague
in the chemistry department, W.F. Libby, who developed
proportional counters to measure the radioactivity of elements such as neodymium, samarium, rubidium and lutetium, to determine their period (Libby 1934). The detection
M. Paterne (&) Á É. Michel Á C. H. et Jean-Claude Dutay
Laboratoire des Sciences du Climat et de l’Environnement,
LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay,
91190 Gif-sur-Yvette, France
e-mail: martine.paterne@lsce.ipsl.fr
© Springer Nature Switzerland AG 2021
G. Ramstein et al. (eds.), Paleoclimatology, Frontiers in Earth Sciences,
https://doi.org/10.1007/978-3-030-24982-3_4
51