Very narrow saturated double-quantum transitions ($2^{2}S\ensuremath{-}3^{2}S, 3^{2}D$) have been observed for atomic H in a He- ${\mathrm{H}}_{2}$ dc discharge using rf and a cw dye laser. The H $3{P}_{\frac{3}{2}}\ensuremath{-}3{D}_{\frac{3}{2}}$ Lamb shift has been measured directly by comparing single- and double-quantum saturation signals to be - 5.5(0.9) MHz, confirming that $3{D}_{\frac{3}{2}}$ lies lower than the $3{P}_{\frac{3}{2}}$ state. Further applications of the method are discussed.Very narrow saturated double-quantum transitions ($2^{2}S\ensuremath{-}3^{2}S, 3^{2}D$) have been observed for atomic H in a He-${\mathrm{H}}_{2}$ dc discharge using rf and a cw dye laser. The H $3{P}_{\frac{3}{2}}\ensuremath{-}3{D}_{\frac{3}{2}}$ Lamb shift has been measured directly by comparing single- and double-quantum saturation signals to be - 5.5(0.9) MHz, confirming that $3{D}_{\frac{3}{2}}$ lies lower than the $3{P}_{\frac{3}{2}}$ state. Further applications of the method are discussed.

Physical Review LettersOct 2, 197817 citations

Very narrow saturated double-quantum transitions ($2^{2}S\ensuremath{-}3^{2}S, 3^{2}D$) have been observed for atomic H in a He-

{\mathrm{H}}_{2}

dc discharge using rf and a cw dye laser. The H $3{P}_{\frac{3}{2}}\ensuremath{-}3{D}_{\frac{3}{2}}$ Lamb shift has been measured directly by comparing single- and double-quantum saturation signals to be - 5.5(0.9) MHz, confirming that

3{D}_{\frac{3}{2}}

lies lower than the

3{P}_{\frac{3}{2}}

state. Further applications of the method are discussed.