Oscillations are shown to exist in the inversion symmetry of the electronic wave function of a hydrogenic atom coherently excited to a Rydberg state by a short pulse of laser radiation in a uniform electric field. The dependence of these oscillations on field strength is shown to scale asn2wherenis the principal quantum number. The possibility of using these oscillations to measure electric signals on picosecond timescales (terahertz frequencies) is suggested. ©1996 American Institute of Physics.