arXiv:1410.3242 · Physical Review A
Magic wavelengths for the 23S→21S transition in helium
Remy Notermans, Robert J. Rengelink, K. A. H. van Leeuwen, W. Vassen
Abstract
We have calculated ac polarizabilities of the $2{\phantom{\rule{4pt}{0ex}}}^{3}S$ and $2{\phantom{\rule{4pt}{0ex}}}^{1}S$ states of both $^{4}\mathrm{He}$ and $^{3}\mathrm{He}$ in the range 318 nm to 2.5 $\ensuremath{\mu}\mathrm{m}$ and determined the magic wavelengths at which these polarizabilities are equal for either isotope. The calculations, only based on available ab initio tables of level energies and Einstein A coefficients, do not require advanced theoretical techniques. The polarizability contribution of the continuum is calculated using a simple extrapolation beyond the ionization limit, yet the results agree to better than $1%$ with such advanced techniques. Several promising magic wavelengths are identified around 320 nm with sufficient accuracy to design an appropriate laser system. The extension of the calculations to $^{3}\mathrm{He}$ is complicated due to the additional hyperfine structure, but we show that the magic wavelength candidates around 320 nm are predominantly shifted by the isotope shift.