Theoretical study of hyperfine structure for low-lying odd-parity levels in singly-ionized thulium

The first measurements of the magnetic dipole hyperfine structure constants A in singly ionized thulium revealed substantial discrepancies with the corresponding theoretical calculations. Subsequent measurements expanded the very limited available dataset and demonstrated that two of the previously reported experimental A values were incorrect, thereby motivating new theoretical calculations. In this work, we employ the configuration interaction method to calculate the A constants for several low-lying levels in Tm II, with the random-phase-approximation corrections also taken into account. Our results show good agreement with the new experimental data and provide reliable predictions for additional states where measurements are not yet available. Additional properties, such as electric dipole transition rates, isotope-shift constants, and electric-field gradients at the site of the nucleus, which are currently of experimental interest can also be calculated within our approach.