  An importent question regarding the dissipation-less current carried by the
edge states in a quantum Hall system is understanding the results of the
electrodynamical interaction among the mobile electrons in the quantum
mechanical limit under a magnetic field B. The interaction affects the
transport parameters, the transverse electric field and the electron velocity.
We have developed a new surface photovoltage spectroscopic technique to measure
the parameters from the transition energies between the electron and heavy hole
edge states. We observe that the measured electron velocity and transverse
(Hall) electric field increase as B^{1/2} and B^{3/2} respectively.
