Ab initio calculations of the spectrum of lawrencium

We present high-accuracy relativistic investigations of the spectrum of Lr, element 103, prompted by the planned optical spectroscopy experiments on this rare and short-lived atom. Reliable predictions of the transition lines are important for the planning and success of these challenging measurements. The relativistic coupled cluster approach was used to calculate the energies of lowest excited states, while the combination of configuration-interaction method with the many-body perturbation theory was employed to address the higher-lying states and to obtain the transition strengths and the lifetimes of the levels of experimental interest. We performed similar calculations for Lu, the lighter homologue of Lr, where experimental data are available. For the lighter element, both the calculated energies and the Einstein coefficients are in excellent agreement with the previously measured values, confirming the accuracy of the performed calculations and the reliability of our predictions for Lr.