Is Xe - Hl a Real Component ?

Introduction. It is known that Xe-HL represents a mixture of (i) rand p-process isotopes generated in a supernova with (ii) isotopically normal Xe identified by the presence of s-process Xe. The question of whether the ultimate mixture of these components has occurred before implantation into presolar diamonds, or whether the components have been implanted separately remains unanswered. Based on the experimental implantation of noble gases into synthetic nanodiamonds it has been concluded that the actual mixture has occurred in the diamonds and that the isotopically normal component is Xe-P3 [1]. This also means that the isotopically anomalous component may not contain Xe at all. On the other hand, analyses of grain size fractions of diamonds separated from the Efremovka CV3 meteorite [2] indicate that Xe-P3 and Xe-HL are effectively separated from each other in the different size fractions because they were implanted at different energies. Since no further separation of Xe-HL into subcomponents is observed in the finest grain size fractions of diamonds it is clear that the Xe-HL was mixed with a component containing s-isotopes (which is not Xe-P3), and then both were implanted simultaneously with similar energies. This would explain why the Xe/Xe ratio in levels off at a value of about 0.71 with decreasing of size of diamond grains. In the present study we have analysed this problem using a set of diamond grain-size fractions separated from the Boriskino CM2 meteorite which contain significantly more low temperature Xe-P3 than the Efremovka diamonds. Results and Discussion. The procedures of isolating diamonds from the meteorite, their separation into grain-size fractions and the results of noble gas analyses during pyrolysis up to 700C with subsequent combustion from 300 to 900C are given in [3]. If the HL gases are a mixture of isotopically anomalous (A) and P3 components released in combustion steps then the (Xe/ Xe)A can be found from the following mixing equations: