Absorption, fluorescence, and fluorescence excitation spectra of pentacene were measured in n-heptane, n-nonane, n-decane, n-dodecane, n-tetradecane, and n-hexadecane at temperature 5 K. We found that the band shift in different matrixes is well described by the intermolecular dispersive interactions with the Onsager cavity radius 5.5 +/- 0.8 Angstrom. Analysis of the fluorescence vibronic structure indicated contribution of 12 totally symmetric vibrations in the frequency range below 2000 cm(-1). The ab initio calculations with 6-31G(d) basis set and semiempirical AMI calculations were carried out to explain the structure of the spectra.