Magnetic-dipole lines in Fe-like and Mn-like molybdenum ions

•Eleven optical spectral lines from Fe-like Mo16+ and Mn-like Mo17+ ions are measured at the newly developed low-energy electron beam ion trap, and ten of these lines are observed for the first time.•The wavelengths and transition probabilities are calculated with the relativistic second-order many-body perturbation theory. Based on these atomic data, spectra simulations are carried out using the collisional-radiative (CR) modeling.•The electron-density dependence of the line intensity ratios is studied using the CR modeling in a wide range of electron densities, i.e., 109-1013 cm−3. The potential applications of these electron-density sensitive lines for plasma diagnostics are discussed.