Enhancement of dielectronic recombination by an electric field

Dielectronic recombination from a continuum of finite bandwidth has been examined down to very low electric fields, 60 mV/cm, with very high resolution, A tunable laser is used to excite atoms to the continuum of finite bandwidth, the broad Ba 6p(3/2)11d autoionizing state, which straddles the Ba+ 6p(1/2) limit. Atoms which make transitions into the high-lying Ba 6p(1/2)nd states and radiatively decay to the bound 6snd states are detected by held ionization. The recombination, integrated over energy, has been measured for fields from 60 mV/cm to 28 V/cm, showing a peak at 0.5 V/cm, in agreement with expectation based an calculations done for other systems. The final-state distribution has been measured, showing that the outer electron remains a spectator in the radiative decay. At fields below 1.0 V/cm and binding energies less than 12 cm(-1) below the Ba+ 6p(1/2) limit we find a deviation of our experimental results from the isolated resonance approximation. [S1050-2947(99)03803-2].