By analyzing stationary absorption and fluorescence spectra of several alpha-oligothiophenes in dichloromethane at room temperature, the S-1 <-- S-0 zero-zero transition energies and Huang-Rhys parameters are determined. Reorientational behaviors of the alpha-oligothiophenes in dichloromethane are also investigated by femtosecond time-resolved fluorescence spectroscopy. The reorientational relaxation observed for each alpha-oligothiophene in its first excited state is interpreted in terms of revolution of a hydrodynamic prolate ellipsoid of which the emission transition dipole is aligned along the long molecular axis. Our results show that a hydrodynamic slip model could successfully explain the reorientation times of alpha-terthiophene, alpha-quaterthiophene, and alpha-quinquethiophene in dichloromethane at 288 K, by modeling these molecules as prolate ellipsoids with dimensions consistent with their van der Weals volumes.