Stark quantum defect orbital ionisation thresholds for the n = 15–20 states of sodium

The recently developed Stark-adapted quantum defect orbital (SQDO) formalism has been employed to calculate field ionisation thresholds for s, p and d states of sodium in the range n = 15–20. The passage from lower to higher fields has been considered to be completely adiabatic. The presently reported values appear to be in very good agreement with the available experimental data.