  We theoretically investigate the interference effect of high-order harmonics
generated from molecules at different alignment angles. It is shown that the
interference of the harmonic emissions from molecules aligned at different
angles can significantly modulate the spectra and result in the anomalous
harmonic cutoffs observed in a recent experiment [ Nature Phys. 7, 822 (2011)
]. The shift of the spectral minimum position with decreasing the degree of
alignment is also explained by the interference effect of the harmonic
emissions.
