Infrared spectroscopy of aniline-X (X = N2, CH4, CHF3, CO) clusters and their corresponding cluster cations in the NH2-stretching vibration region Original Research Article

The NH2-stretching vibrational modes of four different aniline-X clusters (X = N2, CH4, CHF3, CO) and their corresponding cluster cations were investigated by ion-depletion spectroscopy. The observed frequency shifts of the neutral clusters have been found to be very small, and to be proportional to the red shift of the origin of the S1 ← S0 electronic band. This result suggests that the molecules interact with the aromatic ring system of aniline. The shifts of the cation species are larger than those of the neutral species, especially for aniline-CH4+. The proton affinity of the interacting molecule has been found to be correlated to the frequency shift except for CHF3. The different behavior of the cation species from the neutral ones suggests that the main interaction force in the cation clusters is different from that in the neutral ones. The possibility of the hydrogen bond interaction is discussed.