Electric Field Effect In Resonance Lines Of Indium And Thallium

The atomic-beam method has been used to study the Stark effect in the resonance lines of indium ($6s^{2}S_{\frac{1}{2}}\ensuremath{\rightarrow}5p^{2}P_{\frac{1}{2}}$, 4102 \AA{}) and thallium ($7s^{2}S_{\frac{1}{2}}\ensuremath{\rightarrow}6p^{2}P_{\frac{1}{2}}$, 3776 \AA{}). The difference between the atomic polarizability of the $^{2}S_{\frac{1}{2}}$ state and that of the $^{2}P_{\frac{1}{2}}$ state [$\ensuremath{\Delta}\ensuremath{\alpha}(\mathrm{sp})$] has been determined and compared with calculations in the Coulomb approximation. For indium, we find $\ensuremath{\Delta}\ensuremath{\alpha}(\mathrm{sp})=138(11)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ and for thallium $\ensuremath{\Delta}\ensuremath{\alpha}(\mathrm{sp})=115(12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{3}$.