The solvent spectral shifts of the S-0 --> T-1 origin bands of jet-cooled 4H-pyran-4-thione (PT) and 4H-1-benzopyran-4-thione (BPT) were observed in phosphorescence excitation spectra, Van der Waals complexes (1:1) of seed molecules with the carrier gas were observed in several rare gases. In all cases, the combination of a dispersive red-shift and a dipole-induced dipole blue-shift produced a total red-shift, up to a maximum of delta<(nu)over tilde> = -21 cm(-1) for PT-Xe and delta<(nu)over tilde> = -30 cm(-1) for BPT-Xe. Complexes of 1:n (n > 1) were not observable owing to the weakness of the direct S-0 --> T-1 transition. The inductive contributions to the shifts were calculated using values of excited-state dipole moments estimated from solution Stokes shifts; the dipole moments of both molecules in T-1 were found to be close to zero, significantly smaller than their ground-state dipole moments. The phosphorescence excitation spectrum of isolated PT is discussed in some detail. The electronic origin of T-1 at 16 844 cm(-1) is assigned to the transition S-0,S-0 --> T-1z,T-0; the transitions S-0,S-0 reversible arrow T-1(xy,0) are too weak to be detected with this method. Vibronic transitions S-0,S-0 --> T-1z,T-v in PT were analyzed up to excess energies of similar to hc1450 cm(-1).