  We present photoabsorption oscillator strengths for C3H6 molecules with
emphasis on the difference between isomers, cyclopropane and propylene. We use
an iterative numerical method based on the time-dependent local density
approximation with continuum, which we have recently developed. The oscillator
strengths for the two isomers differ at photon energies above their ionization
thresholds. The magnitude and the shape of the oscillator strength distribution
are in good agreement with recent experiments. The differences between the
isomers arise from difference in symmetry of electronic states and different
behaviors of continuum excitations.
