Calculations of the 1s²ns high Rydberg states spectrum of the lithium atom

Ionization potentials and quantum defects of 1s²ns bound states and their adjacent continuum states for the lithium atom are calculated with the R-matrix theory, and then the quantum defect function of the 1s²ns channel is obtained, which varies slowly with the energy based on the quantum defect theory. The initial quantum defect function is calibrated from the most accurate theoretical value of the higher excited state and is used to calculate the quantum defects, ionization potentials, and term energies of the 1s²ns high Rydberg states of the lithium atom. The present calculations may help in performing measurements of the 1s²ns high Rydberg states for the lithium atom.