Determination of the intense-field mass shift of the electron from vacuum polarization on the mass shell

Results for pair production by collision of a laser beam with a bremsstrahlung beam are analyzed to ascertain if the predicted mass increase of an electron in an intense electromagnetic field can be determined from such an experiment. An affirmative conclusion is reached. Measurement of the mass shift requires a comparison of the lowest-order process with higher orders, which are experimentally discernible.