Time-of-flight determination of radiative decay rates for high Rydberg states in atomic nitrogen

State selection by electric field ionization is employed in an atomic beam time-of-flight determination of radiative decay rates for high Ryberg nitrogen atoms, produced by electron impact dissociative excitation of N2. The highest-lying Rydberg states are field ionized; populations of the remaining excited states are modified by in-flight radiative decay. From studies of the atomic beam transit-time distribution at electric fields up to 4.5 kV/cm, radiative decay rates GAMMA/sub n/ have been inferred for states having principal quantum numbers n in the range 199 or approx. =n9 or approx. =35. The data are consistent with an initial population P(n) proportional1/n3 and with GAMMA/sub n/ = (8.8 +- 0.7) x 108 sec-1/n3. Evidence is given that the observed states are p states and that l-changing collisions do not significantly affect the measurements