  We observe nuclear magnetic resonance (NMR) in the fractional quantum Hall
regime at Landau level filling factor $\nu=2/3$ from simultaneous measurement
of longitudinal resistance and photoluminescence (PL). The dynamic nuclear spin
polarization is induced by applying a huge electronic current at the spin phase
transition point of $\nu=2/3$. The NMR spectra obtained from changes in
resistance and PL intensity are qualitatively the same; that is, the Knight
shift (spin polarized region) and zero-shift (spin unpolarized region)
resonances are observed in both. The observed change in PL intensity is
interpreted as a consequence of the trion scattering induced by polarized
nuclear spins. We conclude that both detection methods probe almost the same
local phenomena.
