Multi-photon excitation spectra of the 3snℓ (ℓ = 0, 1, 2 and 3) Rydberg states of magnesium

Abstract

New experimental data on the highly excited ℓ = 0, 1, 2 and 3 Rydberg states of magnesium have been acquired using two-photon and two-step laser excitation technique in conjunction with a thermionic diode ion detector. The new observations include even parity 3sns 1S0 (8 ⩽ n ⩽ 24) and 3snd 1D2 (7 ⩽ n ⩽ 62) Rydberg states approached directly from the 3s2 1S0 ground state via two-photon excitation, and the odd parity 3snp 1P1 (20 ⩽ n ⩽ 61) and 3snf 1F3 (14 ⩽ n ⩽ 66) Rydberg states accessed by the two-step excitation process via 3s4s 1S0 and 3s3d 1D2 intermediate states. The Rydberg relation fit to the new data of the np 1P1 and nf 1F3 series yields the binding energies of the 3s4s 1S0 and 3s3d 1D2 levels as 18 167.702 cm−1 and 15 267.972 cm−1, respectively. By adding the binding energies to the corresponding energies of the aforementioned levels, a precise value of the first ionization potential of magnesium is determined as 61 671.04 ± 0.04 cm−1. Using this ionization potential value, the quantum defects for the ns 1S0, np 1P1, nd 1D2 and nf 1F3 Rydberg series have been determined as 1.526(2), 1.046(2), 0.602(2) and 0.049(2) cm−1 respectively.