The degree of coupling between free electron and nitrogen vibrational temperatures in weakly ionized nozzle expansions of shock‐heated nitrogen has been determined. Free electron temperatures were measured with Langmuir probes while nitrogen vibrational temperatures were determined with a new instrument based on the electron beam technique. The resultant data were analytically correlated by coupling chemical nonequilibrium with nitrogen vibrational and free electron temperature nonequilibrium. It was found that a vibrational loss factor of 7 × 10−4and an effective translational‐rotational loss factor of 4.26 × 10−4best predicted the measured electron temperature distributions.