Forbidden transitions of ultracold Sr$_2$ molecules

We present precision studies of forbidden molecular transitions with ultracold Sr$_2$ in an optical lattice. The molecules are photoassociated from $^{88}$Sr atoms near the $^1S_0$-$^3P_1$ intercombination line. We strongly enable forbidden $\Delta J > 1$ transitions using small magnetic fields, and report doubly forbidden optical magnetic-dipole and electric-quadrupole transitions to subradiant excited states. In magic-wavelength optical lattices, these subradiant states provide very high-Q molecular spectra.