Polarizabilities of Pb2+and Pb4+and ionization energies of Pb+and Pb3+from spectroscopy of high-LRydberg states of Pb+and Pb3+

Abstract

The binding energies of high-$L$ Rydberg levels of Pb${}^{+}$ with $n=19$ or 20 and $6\ensuremath{\leqslant}L\ensuremath{\leqslant}10$ were measured with resonant excitation Stark ionization spectroscopy (RESIS). When combined with previous measurements of members of the $\mathit{nh}$ Rydberg series in Pb${}^{+}$, and analyzed with the long-range polarization model, these determined the polarizability of the $5{d}^{10}6{s}^{2}$ ground state of Pb${}^{2+}$ to be ${\ensuremath{\alpha}}_{d}$ $=$ 13.62(8) a.u. This value is substantially larger than the estimate published recently based on the measured lifetime of the $6s6{p}^{1}{P}_{1}$ resonance level of Pb${}^{2+}$, 7.9(6) a.u. The difference is mostly due to the polarizability of Pb${}^{4+}$, the $5{d}^{10}$ core of the Pb${}^{2+}$ ion. This was established by observation of resolved fine structure in the excitation of $n=39$, high-$L$ Rydberg levels of Pb${}^{3+}$, using the same RESIS technique. Analysis of this spectra determined the polarizability of Pb${}^{4+}$ to be ${\ensuremath{\alpha}}_{d}$ $=$ 3.61(4) a.u. Reanalysis of optical spectra of $\mathit{nh}$ and $\mathit{ng}$ levels in Pb${}^{+}$ and Pb${}^{3+}$ in view of the polarizabilities determined in the RESIS studies indicates revised ionization energies of both ions, ${E}_{\mathrm{I}}$(Pb${}^{+}$) $=$ 121245.28(6) cm${}^{\ensuremath{-}1}$ and ${E}_{\mathrm{I}}$(Pb${}^{3+}$) $=$ 341 435.1(8) cm${}^{\ensuremath{-}1}$.