Two-step laser optogalvanic spectroscopy of the odd-parity Rydberg states of atomic mercury

Abstract

We present new experimental data on the highly excited levels in mercury using the two-step laser excitation and optogalvanic detection technique in conjunction with a RF discharge cell. The 6s7s 3S1 intermediate level has been accessed from the 6s6p 3P2 metastable level that is collisionally populated in the mercury discharge in the presence of a buffer gas at a pressure of about 1 Torr. Two beams fromtwo different dye lasers pumped with a common excimer laser were passed through the discharge cell containing mercury vapors. The first laser was tuned to 6s7s 3S1 level whereas the second laser was scanned covering the wavelength region between 544-458 nm. We have observed the 6snp 3P0 ( $10\le n\le 18$ ), 6snp $^{3}{\rm P}_{1}$ ( $10 \le n \le 41$ ), 6snp $^{3}{\rm P}_{2}$ ( $10 \le n \le 70$ ) and 6snp $^{1}{\rm P}_{1} (10 \le n \le 42$ ) Rydberg series. The 6snp $^{3}{\rm P}_{2}$ Rydberg series to such high n-value has been reported for the first time. The first ionization potential of mercury is determined from the 6snp $^{3}{\rm P}_{2}$ Rydberg series as 84184.15 $\pm $ 0.05 cm-1. Some collisionally induced parity forbidden transitions have also been located that are identified as 6sns $^{1}{\rm S}_{0}$ ( $40 \le n \le 58$ ) series.