  We report experimental results on nonlinear wave coupling in surface wave
turbulence on water at scales close to the crossover between surface gravity
waves and capillary waves. We study 3-wave correlations either in the frequency
domain or in wavevector domain. We observe that in a weakly nonlinear regime,
the dominant nonlinear interactions correspond to waves that are collinear or
close to collinear. Although the resonant coupling of pure gravity waves is
supposed to involve 4 waves, at the capillary crossover we observe a nonlocal
coupling between a gravity wave and 2 capillary waves. Furthermore nonlinear
spectral spreading permits 3-gravity wave coupling. These observations raise
the question of the relevance of these processes in the oceanographic context
and in particular the range of frequencies of gravity waves that may be
impacted.
