  Spin-dependent relaxation and recombination processes in $\gamma$-irradiated
$n$-type Czochralski-grown silicon are studied using continuous wave (cw) and
pulsed electrically detected magnetic resonance (EDMR). Two processes involving
the SL1 center, the neutral excited triplet state of the oxygen-vacancy
complex, are observed which can be separated by their different dynamics. One
of the processes is the relaxation of the excited SL1 state to the ground state
of the oxygen-vacancy complex, the other a charge transfer between $^{31}$P
donors and SL1 centers forming close pairs, as indicated by electrically
detected electron double resonance. For both processes, the recombination
dynamics are studied with pulsed EDMR techniques. We demonstrate the
feasibility of true zero-field cw and pulsed EDMR for spin 1 systems and use
this to measure the lifetimes of the different spin states of SL1 also at
vanishing external magnetic field.
