  Interactions between multipolar nuclear transitions and gravitational waves
(GWs) are theoretically investigated. Two nonclassical scenarios of the GW
detection are suggested. We demonstrate in this report that the long-lived
Moessbauer nuclides of multipolar transitions are suitable transducers to
detect the impinging GWs. Shape deformation and spin flip of nucleus are
derived from the Hamiltonian with gravity interaction. The GWs generate a
nuclear quadrupole deformation in analogy with the Stark effect, of which the
electric field generates the dipole deformation of electron orbits. Likewise in
analogy with the nuclear magnetic resonance that the rotating radio-frequency
field flips the nuclear spin, the GWs flip the nuclear spin by the resonant
helicity-rotation-gravity coupling. The high energy states of the quadrupole
deformation in heavy nuclides can dramatically speed up the multipolar
transitions, which may be important for the GW detection particularly in the
low frequency band, ranging from 100 nHz to 1 Hz.
