  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.
