Abstract A full vibrational analysis was recently made for the H3N+CH2CH2N+H3 ion, on the basis of infrared measurements, and a partial vibrational assignment proposed1. The observed fundamentals were interpreted In terms of a C2h, symmetry for the ion. There are thirty-six fundamentals (r - llag + 8Au + 7Bg + 10Bu; Ag and Bg Raman-active only; Au and Bu infrared-active only). In addition to the eighteen infrared-active vibrations, a number of bands was observed which were assigned as formally forbidden Raman-active modes, excited by strong hydrogen bonding causing departure from the exact site symmetry of the species.