Reconciliation of Experimental Lamb Shifts

We develop a detailed analysis of the metastable quenching problem encountered in our recent level-crossing measurements in the $n=2$ state of atomic hydrogen. The analysis allows calculation of a previously unaccounted systematic correction to the value of the Lamb shift S derived from these measurements. This correction, together with refinements in the calculation of S from a measured crossing, decreases our value to S=1057.86±0.10 MHz. Within experimental error, this value agrees with the original result as measured by Lamb and collaborators. In addition, the analysis allows the calculation of a new upper limit to the parity impurity amplitude in the $2S$ state of atomic hydrogen, namely |a₀|²≤8×10^-9, at zero magnetic field.