Both temporally and spectrally resolved fine structures of 90° lateral (3/2)ω0 harmonic emission were experimentally observed. The existence of (3/2)ω0 harmonic filaments is attributed to formation from the moving filament bottom at its transient nc/4 surface. The double hump structure with its intense red hump of laterally emitted (3/2)ω0 spectrum can also be explained by a Doppler correction in addition to the thermal correction. Estimation of both red and blue spectral shifts with our simple model is qualitatively consistent with experimental results. Experiments showed that the (3/2)ω0 emission was evidently suppressed by using a broad band laser. This may be promising for superhot electron suppression.