Relativistic unitary coupled cluster theory and applications

Abstract

We present the formulation and application of relativistic unitary coupled cluster theory to atomic properties. The remarkable features of this theory are highlighted, and it is used to calculate the lifetimes of 5d2D3/2 and 6p2P3/2 states of Ba+ and Pb+ respectively. The magnetic dipole hyperfine constants for the 6s2S1/2 state of Ba+ and the 6p2P3/2 state of Pb+ have also been calculated. The results clearly suggest that it is very well suited for accurate ab initio calculations of properties of heavy atomic systems. The present calculation of lifetime for Ba+ gives an improvement over the previously calculated values using ordinary coupled-cluster theory, although we have observed that the decay of the excited state via the magnetic dipole channel is even more important.