FIELD-ENHANCED RADIATIVE RECOMBINATION AT LOW ENERGIES

The effect of external time-dependent electric fields (TDF) on the radiative recombination (RR) process near the zero energy threshold and for capture to high Rydberg states is examined in detail. The momentum coherence phenomenon discovered recently causes a large enhancement in the cross section, with the maximum located near the principal quantum number n(g) congruent-to Z/g, where Z is an effective charge of the ion and g is the field momentum defined by the time integral of the electric field perturbation. The sensitivity of the RR cross sections on TDF may be used to study the field conditions in the interaction region where the recombination reaction takes place. Dependence of the enhancement on field parameters is presented in a form suitable for data analyses. Calculated cross sections are compared with recent experiments on Ar15+ and U28+, Au25+ and on ions with Z < 25, where sizable enhancements were observed.