Nature 301, 690 - 692 (24 February 1983); doi:10.1038/301690a0

Accelerator mass spectrometry measurement of cosmogenic ²⁶Al in terrestrial and extraterrestrial matter

G. M. Raisbeck^*, F. Yiou^*, J. Klein^† & R. Middleton^†

^*Laboratoire René Bernas, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, 91406 Orsay, France
^†Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-3859, USA

Cosmogenic ²⁶Al (half life = 7.2 10⁵ yr) and ¹⁰Be (1.5 10⁶ yr) are produced continually in the atmosphere by cosmic rays. They are fixed on aerosol particles and, after a relatively short time (1 yr) precipitate to the Earth's surface, and from there into various geophysical reservoirs. The possibility of using this pair of isotopes as a dating tool, independent of cosmic ray intensity variations, was discussed some time ago¹. However, except for several rare exceptions^2,3 the very low activities of these isotopes, especially ²⁶Al, have dissuaded workers from such studies by classical radioactive counting techniques. The development of accelerator mass spectrometry offers to change this situation dramatically. Cosmogenically produced ¹⁰Be has already been measured by several groups using accelerator mass spectrometry⁴. While the technique has also been used to detect artificially produced⁵⁻⁷ and extraterrestrial⁸, ²⁶Al the ²⁶Al/²⁷Al ratio in each case was several orders of magnitude greater than that expected in natural terrestrial samples. We report here the first accelerator mass spectrometry measurements of ²⁶Al in natural terrestrial samples, and give a value for the atmospheric production ratio of ²⁶Al/¹⁰Be, an essential parameter for use of this pair as an absolute dating tool. To demonstrate the potential of our technique for measuring ²⁶Al in small quantities of extraterrestrial material, we have also measured this isotope in milligramme-size samples of lunar soil. Finally, by measuring the absolute ²⁶Al/²⁷Al ratio of two samples whose radioactive disintegration rate was known, we have obtained an independent check on the ²⁶Al half life.

References

1.	Lal, D. J. oceanogr. Soc. Japn. 20th Anniv. Vol. 18, 600−614 (1962).
2.	Reyss, J. L., Yokoyama, Y. & Tanaka, S. Science 193, 1119−1121 (1976). | ISI | ChemPort |
3.	Guichard, F., Reyss, J. L. & Yokoyama, Y. Nature 272, 155−156 (1978). | ISI | ChemPort |
4.	Proc. Symp. on Accelerator Mass Spectrometry (Argonne National Laboratory Rep. ANL/PHY-81-1, 1981).
5.	Raisbeck, G. M., Yiou, F. & Stephan, C. J. phys. Lett. 40, L241 (1979). | ISI |
6.	Kilius, L. R. et al. Nature 282, 488 (1979). | ISI | ChemPort |
7.	Paul, M., Henning, W., Kutschera, W., Stephenson, E. J. & Yntema, J. L. Phys. Lett. 94B 303 (1980). | Article | ISI |
8.	Thomas, J. H., Parker, P., Herzog, G. & Pal, D. Nucl. Instrum. Meth. (in the press).
9.	Leifer, R., Tookel, L. E. & Larson, R. USDOE Rep. EML-375 (1981).
10.	Raisbeck, G. M. et al. Geophys. Res. Lett. 8, 1015−1018 (1981). | ISI | ChemPort |
11.	Middleton, R. in Proc. Symp. of Northeastern Accelerator Personal (ed. Billen, J. H.) 134 (University of Wisconsin, 1980).
12.	Klein, J., Middleton, R. & Tang, H. Q. Nucl. Instrum. Meth. 193, 601 (1982). | Article | ISI | ChemPort |
13.	Raisbeck, G. M., Yiou, F., Fruneau, M. & Loiseaux, J. M. Science 202, 215 (1978). | ISI |
14.	Reyss, J. L., Yokoyama, Y. & Guichard, F. Earth planet. Sci. Lett. 53, 203 (1981). | Article | ISI | ChemPort |
15.	McCorkell, R., Fireman, E. L. & Langway, C. C. Jr, Science 158, 1690 (1967). | ISI | ChemPort |
16.	Raisbeck, G. M. & Yiou, F. Phys. Rev. C9, 1385 (1974). | Article | ISI | ChemPort |
17.	Raisbeck, G. M. & Yiou, F. Nucl. Instrum. Meth. 196, 483 (1981). | Article |
18.	Apollo Preliminary Science Rep., NASA, SP-315, 7 (1972).
19.	Gibson, E. K. Jr & Moore, G. W. Science 179, 69 (1973). | ISI | ChemPort |
20.	Bogard, D. D., Nyqiust, L. E., Hirsch, W. C. & Moore, D. R. Earth planet. Sci. Lett. 21, 52 (1973). | Article | ISI | ChemPort |
21.	Viste, E. & Anders, E. J. geophys. Res. 67, 2913 (1962). | ISI | ChemPort |
22.	Pal, D. K., Tuniz, C., Moniot, R. K., Kruse, T. H. & Herzog, G. F. Science 218, 787 (1982). | ISI | ChemPort |
23.	Nishiizumi, K., Regnier, S. & Marti, K. Earth planet. Sci. Lett. 50, 156 (1980). | Article | ISI | ChemPort |
24.	Müller, O., Hampel, W., Kirston, T. & Herzog, G. F. Geochim. cosmochim. Acta 45, 447 (1981). | Article |
25.	Rightmire, R. A., Kohman, T. P. & Hintenberger, H. Z. Naturforsch. 13a 847 (1958). | ISI |
26.	Samworth, E. A., Warburton, E. K. & Engelbertink, G. A. P. Phys. Rev. C5, 138 (1972). | Article | ISI |