FSRCC two-valence calculations of clock transition properties, dipole polarizability and isotope shifts in Fermionic and Bosonic Sr

Abstract

We employ an all-particle multireference Fock-space relativistic coupled-cluster (FSRCC) theory to study the $5s^2{\;^1}S_0 - 5s5p{\;^3P^o_0}$ clock transition in both Fermionic and Bosonic isotopes of Sr. We compute the excitation energies, E1 and M1 transition amplitudes, hyperfine reduced matrix elements, and isotope shifts using FSRCC theory. Further, we calculate the lifetime of the metastable clock states for $^{87}$Sr and $^{88}$Sr. Furthermore, we employ perturbed relativistic coupled-cluster (PRCC) theory to compute the ground state electric dipole polarizability of Sr. To improve the accuracy of our results, we incorporate the corrections from the relativistic and quantum electrodynamical (QED) effects, and perturbative triples to all our calculations. Our computed excitation energies are in good agreement with the experimental data for low-lying excited states. Our results for E1, M1 and HFS reduced matrix elements are within the experimental error bars, however, with slight difference from the previous calculations due to more accurate treatment of electron correlations in our calculation. Our computed lifetime of the clock state for $^{87}$Sr is within the error bars of the available experimental results, whereas for $^{88}$Sr, it is an order of magnitude smaller than the only available calculation using model potential. Our PRCC result for the ground state polarizability is in good agreement with the experiment, and smaller than previous calculations. As can be expected, our FSRCC results on isotope shift parameters show differences from the MCDF calculations. From the detailed analysis of our results, we find that the corrections from the Breit interaction, QED effects, and perturbative triples are crucial to get accurate clock transition properties in Sr.