Electromagnetic multipole moments and transitions

For the \( M1 \) operator the radial matrix element is $$ < k_{a}\vert r^{0}\vert k_{b}>\, = \delta _{n_{a},n_{b}}, $$ and the SPME simplify to: $$ \langle k_{a}\vert\vert O(M1,s)\vert\vert k_{b}\rangle=\sqrt{ \frac{3}{4\pi }}\langle j_{a}\vert\vert \mathbf{s}\,\vert\vert j_{b}\rangle \delta _{n_{a},n_{b}}g^{s}_{q}\mu_{N} $$ $$ =\sqrt{ \frac{3}{4\pi }}(-1)^{l _{a}+j_{a}+3/2} \sqrt{(2j_{a}+1)(2j_{b}+1)}\left\{\begin{array}{ccc} {1/2}& {1/2} & {1} \\ {j_{b}} & {j_{a}}& {l _{a}}\end{array}\right\} $$ $$ \times\langle s\vert\vert \mathbf{s}\vert\vert s\rangle \delta _{l _{a},l _{b}} \delta _{n_{a},n_{b}}g^{s}_{q}\mu _{N}, $$