We show that there are two reasons why the partial width for the transition 1ð ð3SÞ ! þ b1ð1PÞÞ is suppressed. First, the spin-averaged matrix element Ið3Sjrj1PJÞ is small, being equal to 0:023 GeV 1 in our relativistic calculations. Secondly, the spin-orbit splittings produce relatively large contributions, giving Ið3Sjrj1P2Þ 1⁄4 0:066 GeV , while due to a large cancellation the matrix element...
