Molecular beam photoionization study of HgCl2

Abstract

High resolution (0.14 Å FWHM) photoionization efficiency (PIE) data for HgCl+2 have been obtained in the region 730–1100 Å using an oven-type supersonic beam source. The ionization energies of the spin-orbit states X̃ 2Π3/2g and 2Π1/2g were determined to be 11.380±0.003 and 11.505±0.003 eV, respectively. The major fragment ions observed in the region 600–1300 Å are HgCl+, Hg+, and Cl+ having appearance energies of ≤11.041, 12.594±0.018, and 16.721±0.032 eV, respectively. The latter value allows the calculation of the bond dissociation energy for HgCl to be 21.1±2.2 kcal/mol. This study further revealed members of autoionizing Rydberg series converging to the 2D±5/2 and 2D±3/2,±1/2 states at 16.715±0.003 and 18.65 eV, respectively, which exhibit highly asymmetric Beutler–Fano line profiles. The comparison of the PIE curve for Hg+ from Hg and those for HgCl+2 and its fragments unambiguously shows that autoionizing Rydberg series resolved in this study can be assigned to transitions [(5d)10σ2gσ2uπ4uπ4g] → [(5d)9σ2gσ2uπ4uπ4g 2D±5/2] np and [(5d)10σ2gσ2uπ4uπ4g] → [(5d)9σ2gσ2uπ4uπ4g 2D±3/2,±1/2] np, n≥6, which are mainly associated with the mercury atom in HgCl2.