Effect of a chemical bond on the atomic capture of negative muons in matter

The main features of the Au-Yang and Cohen model are analysed which accounts for the dependence of μ- atomic capture on atomic number Z in oxides. It is noted that the use of the Pauling formula to calculate the charge transfer parameter Z is not rightful. The other assumption of the model in question concerning the monotonous increase of the relative capture probability of muons by a cation in MgO as a function of Zsub(f) and its use as a normalizing curve for other oxides were experimentally tested. For this purpose muon-capture data are considered in a number of compounds which are isoelectronic with respect to MgO. The analysis shows that an increase in the charge transfer parameter and effective cation charge when passing from WH4+ and Na+ to Mg2+ leads to a decrease in the relative capture probability. The notion of the ionic and covalent charges of the chemical bonds of atoms oppositely influencing muonic capture is introduced to explain the observed regularities in μ- capture in oxides and halogenides