Photorecombination of berylliumlike Ti18+: Hyperfine quenching of dielectronic resonances

The photorecombination spectrum of 48Ti18+ was measured employing the merged electron-ion beams technique at a heavy-ion storage ring. The experimental electron-ion collision energy range 0-80 eV comprises all dielectronic recombination (DR) resonances associated with 2s->2p (Delta N =0) core excitations as well as trielectronic recombination (TR) resonances that involve 2s2->2p2 core double-excitations. At low collision energies DR resonances are observed that are associated with the excitation of metastable 2s2p 3P0 primary ions with nearly infinite lifetime for the isotope 48Ti with zero nuclear spin. For the isotope 47Ti with nonzero nuclear spin hyperfine quenching of these resonances occurs. The procedure for obtaining the associated time constant from a recombination measurement is outlined.