Dielectronic recombination into high-n Rydberg shells

The dielectronic recombination (DR) of multiply and highly charged ions often proceeds due to the capture of electrons into high-n Rydberg orbitals. The formation of these high-n resonances is relevant to the dynamics of low-temperature plasma and has been explored especially for the DR of initially lithium-like ions. Despite the great interest in low-temperature plasma rate coefficients for different ions, however, several difficulties have hampered the modeling of high-n resonances owing to their complex shell and fine structure, or merely the size of these ions in their doubly excited state. To improve the modeling of DR processes with high-n Rydberg orbitals, we here expand and illustrate the use of JAC, the Jena Atomic Calculator. In particular, we now support several empirical corrections in order to synthesize DR spectra for a wide range of positive ions. This expansion also prepares JAC for a new class of storage-ring experiments that aim for determining improved valence-shell excitations energies of (highly charged) beryllium- and other few-electron ions. To demonstrate this expansion of the JAC code, we here compute and discuss the low-lying DR resonances of initially beryllium-like Pt\(^{78+}\) ions and compare the predicted spectra with previous measurements and computations. Beside this rather uninvolved example, the JAC toolbox is suitable for many other, if not most, multiply and highly charged ions across the periodic table.

Well-known difficulties and challenges in dealing with high-n dielectronic recombination (DR) computations