  A collapse and revival shape of Rabi oscillations of a single
Nitrogen-Vacancy (NV) center electron spin has been observed in diamond at room
temperature. Because of hyperfine interaction between the host 14N nuclear spin
and NV center electron spin, different orientation of the 14N nuclear spin
leads to a triplet splitting of the transition between the ground ms=0 and
excited states ms=1. Microwave can excite the three transitions equally to
induce three independent nutations and the shape of Rabi oscillations is a
combination of the three nutations. This result provides an innovative view of
electron spin oscillations in diamond.
