Accurate energies of nS, nP, nD, nF, and nG levels of neutral cesium.

Abstract

Extensive measurements have been performed to determine the absolute energies of the n ${\mathrm{}}^{2}$${S}_{1/2}$ (n=8--31), n ${\mathrm{}}^{2}$${P}_{1/2}$ (n=6,9--80), n ${\mathrm{}}^{2}$${D}_{5/2}$ (n=5,7--36), n ${\mathrm{}}^{2}$${F}_{5/2}$ (n=6--65), and n ${\mathrm{}}^{2}$${G}_{7/2}$ (n=6--54) levels of Cs by using nonresonant and resonantly enhanced Doppler-free two-photon spectroscopy. The excitation mechanisms employed include resonantly enhanced dipole-quadrupole and quadrupole-quadrupole transitions. All energies were measured directly with respect to the 6 $^{2}S_{1/2}$ ground state. The laser wavelengths were measured by high-precision Fabry-Perot interferometry yielding an uncertainty of 0.0002 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ for most Cs levels. Ionization energies derived by fitting the modified Ritz formula to each of the five series observed coincide within 0.000 05 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Taking account of possible systematic errors, the Cs ionization energy is 31 406.467 66(15) ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$.