When heated by reflected shock waves to temperatures between 1400 and 1700 K at pressures of approximately 12-15 arm, mixtures of acetonitrile in argon (0.4-7 mol %) exhibit strong banded absorption in the ultraviolet region between 320 and 250 nm. The carrier of the absorption spectrum is ketene imine, H2C=C=NH. Time-resolved spectra of ketene imine have been recorded with exposure times between 100 and 200 mu s using a charge-coupled device (CCD) with an imaging spectrograph. Through the use of the technique of pixel binning, temporal profiles of formation and equilibration of ketene imine have been obtained with a time resolution of 24 mu s. The rearrangement of ketene imine <-> acetonitrile has been studied using ab initio quantum chemical techniques. The calculations predict the rate-determining step in the rearrangement process to be the 1,2-hydrogen transfer of the imine hydrogen to the adjacent carbon atom to produce vinyl nitrene. With the aid of the ab initio results, the experimental rate data for the reaction ketene imine --> acetonitrile have been extrapolated to the high-pressure limit, yielding the rate constant expression k(infinity) = 10(13.4(+/-0.5)) exp(-294(+/-14) kJ mol(-1)/RT) s(-1).