Measurement of the field-induced dielectronic recombination rate enhancement of N4+ ions differential in the Rydberg quantum number n

Abstract Field-enhanced dielectronic recombination (DR) cross-sections differential in the main quantum number n have been measured for N 4+ ions. The n -differential data were obtained at the heavy ion storage ring CRYRING by increasing the ion energy in two steps from 3 to 5 MeV/u and from 5 to 7.5 MeV/u. The accompanying increase of the magnetic field in the storage – ring dipole magnets leads to a decrease of the cutoff quantum number n c associated with the field ionization of intermediate N 3+ (1s 2 2p nl ) states. By comparing measurements at two different ion energies the enhancement of DR due to electromagnetic fields is derived for the narrow bandwidths of Rydberg states n ≈17–21 and 19–24. The applied electric fields ranged from 0 to 300 V/cm. The observed enhancement was up to a factor of 1.9 for the bandwidth n ≈17–21 and up to 2.3 for the bandwidth n ≈19–24, respectively.