A laser flash photolysis and time-resolved resonance Raman study of 1-nitronaphthalene (1NN) in sodium nitrite and trans-stilbene (tS) solution, in both polar and nonpolar solvents, is reported. The transient absorption data suggest that 1NN acts as an electron acceptor with nitrite ions and tS in polar solvents but undergoes energy transfer to tS in nonpolar solutions. At high concentrations of tS the electron-transfer reaction leads ultimately to the formation of a dimer radical cation (tS(2))(.+). We report here the Raman spectrum of the radical anion of 2-nitronaphthalene and the differences in the Raman spectra of the monomeric and dimeric radical cation of trans-stilbene in the 1500-1650 cm(-1) region. The switch from energy to electron transfer when going from nonpolar to polar solutions is discussed in terms of the electronic and nuclear factors that govern these reactions.