Collisional perturbation of states in atomic ytterbium by helium and neon

Results of an investigation of collisional deexcitation of the metastable $6s6p{}^3{P}_0$ state in atomic ytterbium by helium and neon buffer gases are reported. We find upper limits for the quenching cross sections to be ${\sigma }_{\mathrm{He}}<13\mathrm{}\times {10}^{-22}{\mathrm{cm}}^2$ and ${\sigma }_{\mathrm{Ne}}<8\mathrm{}\times {10}^{-22}{\mathrm{cm}}^2.$ The small cross sections may allow an ytterbium parity nonconservation experiment to be performed in a vapor cell. We have also measured the pressure broadening and shift of the $6s6p{}^3{P}_0\to 6s7s{}^3{\mathrm{S}}_1$ and ${6s}^2{}^1{S}_0\to 6s6p{}^3{P}_1$ transitions by helium and neon.