PRODUCTION RATES OF COSMOGENIC NUCLIDES

Voshage H. and Hintenberger H. (1963) The cosmic-ray exposure ages of iron meteorites as derived from the isotopic composition of potassium and the production rates of cosmogenic nuclides in the past. In Radioactive Dating, International Atomic Energy Agency, Vienna, pp. 367-379. 

Begemarm F, Schultz L (1988) The influence of bulk chemical composition on the production rate of cosmogenic nuclides in meteorites. Lunar Planet Sci IXX, Lunar Planet Institute, Houston, p 51-52... 

PRODUCTION RATES OF COSMOGENIC NUCLIDES Experimental determinations of production rates... 

The stable cosmogenic nuclides used for measuring CRE ages are He, Ne, Ar, Kr, or Xe. The production rates of these nuclides can be calculated from... 

Be produced by cosmic-ray-induced nuclear reactions is useful for studying atmospheric transport mechanisms. Since the production of Be and other cosmogenic nuclides is directly dependent on the cosmic-ray intensity, a relationship between the production rate of these nuclides and the 11-year solar cycle has been found (Kulan et al. 2006). It is known that the galactic cosmic-ray intensity at the earth s orbit is inversely related to solar activity (Hotzl etal. 1991). 

Dunai TJ (2000) Scaling factors for production rates of in situ produced cosmogenic nuclides A critical reevaluation. Earth Planet Sci Lett 176 157-169... 

Soil production is a function of sod depth (Heimsath et al., 1997), parent material, and environmental conditions (Heimsath et al.,1999). As soil thickens, the rate of the conversion of the underlying rock or sediment to sod decreases. This has been shown using field observations of the relation between soil thickness and the abundance of cosmogenic nuclides ( °Be and A1) in the quartz grains at the rock-soil interface (Figure 24). From this work, soil production can be described by... 

Figure 2. Dependence of cosmogenic nuclide production rates on altitude and latitude, as derived from the scaling methods of Lai (1991) and Dunai (2000a), respectively. Production rates are normalized to Po, the value at sea level and high latitudes. Though the curves look similar at first glance, differences between the two scaling methods become increasingly evident at higher altitudes. Near sea level, the largest differences occur at latitudes 20-40° as shown in the insets.

Figure 10. Temporal evolution of the concentration of a stable cosmogenic nuclide in dependence of the erosion rate, for a production rate of 1 atom g a f Expected concentrations in real samples can be calculated by multiplying the values from this plot with the actual production rate.

When the early studies of cosmogenic nuclides in terrestrial surface rocks were published, production rates were (quite poorly known. Davis and Schaeffer (1955) and Phillips et al. (1986) estimated the C1 production rate from the cosmic ray neutron flux and the thermal neutron capture cross section of Cl. Srinivasan (1976) scaled the Xe production rate from the lunar surface to the Earth s surface by considering the attenuation of cosmic rays all through the atmosphere. Kurz (1986a,b), Craig and Poreda (1986), and Porcelli et al. (1987) used the production rate as calculated by Yokoyama et al. (1977) to estimate the He production rate. The problem with such estimates was a... 

Production rates by muons. Experimental determinations of cosmogenic nuclide production by muons are scarce, and for noble gases even absent. In a depth profile from lateritic soil in the Congo, Brown et al. (1995a) were able to discern the muon-produced component of e in quartz and constrain its contribution at the surface (300 m altitude)... 

In this respect the work of Masarik and Reedy (1995) was a major step forward. These authors relied on cross sections as derived from measurements in extraterrestrial samples, where at sufficient shielding depths cosmogenic nuclide production is dominated by neutrons also. Indeed their production rates agree remarkably well with experimental values (Table 6). In a follow-up paper, Masarik and Reedy (1996) reported elemental coefficients for the production rates of °Be, Al, Cl as well as He and... 

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