All-electron Douglas-Kroll-Hess and pseudopotential study on the low-lying states of uranium hydride UH

Multireference configuration interaction (MRCI) calculations combined with the all-electron scalar-relativistic Douglas-Kroll-Hess (DKH) Hamiltonian, as well as a relativistic energy-consistent small-core pseudopotential (SPP) for uranium, have been performed to study the low-lying electronic ΛS states of uranium monohydride UH with term energies below ≈0.5 eV. After taking spin-orbit effects into account both DKH/MRCI and SPP/MRCI calculations predict a 4I9/2 ground state. The calculated ground state molecular constants of both approaches show a good agreement with each other (MRCI + Q, DKH: Re = 2.021 Å, ωe = 1483 cm−1, De = 2.79 eV; SPP: Re = 2.011 Å, ωe = 1497 cm−1, De = 2.85 eV), as well as with available experimental data (ωe = 1424 cm−1 in argon matrix).