Pion capture probabilities in tissues and tissue-equivalent materials

From measurements of X-rays emitted when a negative pion stops in a material, the relative capture probabilities in various elements can be deduced. Results are presented for the ratios of captures in carbon to captures in oxygen for pig tissues and several tissue-equivalent and lyoluminescent materials. Comparison is made with the Fermi-Teller law, which proves to be quite inadequate, and in selected cases also with a model which takes into account molecular effects and transfer of pions initially captured on hydrogen. The implications of the results for pion dosimetry are discussed.