  We investigate how short and long electron trajectory contributions to high
harmonic emission and their interferences give access to intra-molecular
dynamics. In the case of unaligned molecules, we show experimental evidences
that the long trajectory signature is more dependent upon the molecule than the
short one, providing a high sensitivity to cation nuclear dynamics within 100's
of as to few fs. Using theoretical approaches based on Strong Field
Approximation and Time Dependent Schrodinger Equation, we examine how quantum
path interferences encode electronic motion whilst molecules are aligned. We
show that the interferences are dependent on channels superposition and upon
which ionisation channel is involved. In particular, quantum path interferences
encodes electronic migration signature while coupling between channels is
allowed by the laser field. Hence, molecular quantum path interferences is a
promising method for Attosecond Spectroscopy, allowing the resolution of
ultra-fast charge migration in molecules after ionisation in a self-referenced
manner.
