Half-Life ofBe10

Abstract

analysis of (6b) shows that for a 4-0, a continuous displacive transition will occur at some X c (a) with X c (a) an increasing function of a. An interesting feature of this instability-driven transition is that the transition becomes increasingly sharp as a -0. Thus, if this were used to model a real physical system, a case could occur in which it would be impossible experimentally to determine that the transition was not first order. The results for (6b) are as shown in Table I. In conclusion, a clearer picture of the transition found in Ref. 4 is now available. In the absence of a symmetry-breaking term there should be no transition. In the presence of one (which could be implicitly introduced through the MFA), there should be a second-order transition. These results are for an idealized model. In a real, physical system, there should be at least a weak symmetry-breaking term. Then, since the transition is of the instability-driven type (with the instability of the Coulomb lattice providing an effective "hump" for the TO mode) there would be a sharp second-order transition with almost a first-order character. If this were accompanied by, for example, a lattice distortion, the transition could be a real, first-order transition.Cosmogenic radionuclides having very long half-lives can be useful dating tools in a number of astrophysical, geophysical, and cosmochemical problems. One of the most prominent of such species is the nuclide 10 Be, which has significant applications in studying the history of cosmic rays, 1 meteorites, 2 lunar samples, 3 marine sediments, 4 and polar deposits. 5 The generally accepted 6 half-life of 10 Be is (2.7 ±0.4)xi0 6 yr, a value based on two separate experiments carried out more than 20 years ago. 7, 8 We have become interested in the question of the accuracy of this number because of its importance in trying to "date" cosmic-ray ages. 1 Although we had no reason to suspect a large error Thus, the first-order character of either the MFA or SPA treatment of the instability-driven transition should not be considered spurious, but rather a strong indication of the inherent instability of the system.We are especially appreciative of a critical examination of our results by W. J. Camp.Any quartic Hamiltonian with a single degree of freedom can be scaled to the form (6). This is also the region where k B T is of the order of the depth of one of the minima of the effective doublewell potential associated with the long-wave length optic mode.in the accepted value, we felt its widespread use warranted an attempt to reduce the error limits. While we have not yet succeeded in that goal, we have found a value which is in strong disagreement with the older number, and which should have important implications in a number of fields of study.The two essential quantities in the determination of any half-life which is too long to be followed directly are the decay rate and the number of atoms of the decaying species, Usually the former can be measured directly, while the latter is obtained by a ma...

Subduction dynamics at the middle America trench : new constraints from swath bathymetry, multichannel seismic data, and 10BE

“…As lOBe has a relatively short half-life of 1.5 x 106 yrs (Yiou and Raisbeck, 1972), it is only found in significant concentrations in the upper tens of meters of marine sediment. Enrched concentrations of lOBe have been detected in arc volcanic lavas, but not in other mantle-derived rocks such as MORB, OIB, and continental flood basalts (Brown et al, 1982;Tera et al, 1986;Ryan and Langmuir, 1988;Monaghan et al, 1988;Morris and Tera, 1989;.…”

“…lOBe reaches the ocean via precipitation, where it then adsorbs onto particulate matter settling to the ocean floor. As lOBe has a half-life of 1.5 x 106 yrs (Yiou and Raisbeck, 1972), it is only found in significant concentrations in the upper tens of meters of marine sediment.…”

“…lOBe is cared via precipitation to the ocean, where it is highly paricle adsorptive (e.g., Kusakabe et aI., 1987). Due to its relatively short half-life of 1.5 x 106 yrs (Yiou and Raisbeck, 1972), lOBe is typically only found in significant concentrations in the upper tens of meters of marne sediment. As mantle values for lOBe are below detection limits, the presence of enriched concentrations of lOBe detected in arc lavas requires that the youngest sediment be subducted to the arc volcanic roots (Brown et al, 1982;Tera et al, 1986;Ryan and Langmuir, 1988;Monaghan et al, 1988;Morris and Tera, 1989;Morrs et al, 1990).…”

Costa Rica Accretionary Wedge

“…It is strongly adsorptive on settling sediment particles in the oceans, and has a half-life of 1.5 m.y. ; therefore, 10 Be tags only the uppermost part of the sediment column (Lal and Peters, 1967;Anderson et al, 1990;Yiou and Raisbeck, 1972). This is shown by measurements for DSDP Site 495, off the coast of Guatemala (Fig.…”

La météorisation sur les hauts plateaux de la Gaspésie (Québec) : quelques aspects

“…(1960) ont démontré le potentiel de cet isotope pour établir la géochronologie des sédiments marins. La demi-vie du 10 Be, estimée à 1,5 Ma par Yiou et Raisbeck (1972), rend, en effet, cet isotope attrayant comme outil de datation du Quaternaire et de la fin du Tertiaire. Le 10 Be a ensuite été retracé dans les glaces polaires (Raisbeck et al, 1978), dans l'eau des préci-pitations (Raisbeck étal., 1979), et dans les sols (Brown etal., 1981).…”