Experimental Evidence for Magnetic Field Effects on Dielectronic Recombination via High Rydberg States

We report the first experimental observation of magnetic field effects on dielectronic recombination (DR) via highly excited Rydberg levels. Crossed static electric and magnetic fields E_y and B_z were imposed on the collision region in high resolution DR measurements with Li-like Cl¹⁴⁺ ions at the heavy ion storage ring TSR in Heidelberg. Enhancement of DR rate coefficients α for the group of high Rydberg states attached to the 2p_1/2 and 2p_3/2 series limits was observed when motional electric fields E_y up to 380 V/cm were introduced. The associated enhancement rate dα/dE_y which we found to be constant at least for E_y≤100 V/cm decreased by almost a factor of 2 when the longitudinal field B_z was increased from 20 to 69 mT.