The suggestion, that the + SR signal from crystalline material at 37K arose from N2Mu+, was considered with respect to  ab initio  calculations which had been made by using Hartree-Fock, second-order Møller-Plesset, quadratic configuration interaction and density functional methods. It was concluded that the intrinsic N quadrupole interaction (2.26MHz) was too large, by a factor of more than 2, to be attributed to N2Mu+. Calculations were also performed for the linear complex, [N2MuN2]+. This was shown to be more stable, and to give a quadrupole interaction that was closer to the experimental value.

T.A.Claxton: Philosophical Magazine B, 1995, 72[2], 251-7