Rotational structure near the local mode limit in the (3000) band of germane

In recent years there have been extensive experimental searches for bond selectivity. However, actual energy localization has not been achieved due to very fast intramolecular vibrational relaxation (IVR). We have recently reported [Zhu, Thrush, and Robiette, Chem. Phys. Lett. 150, 181 (1988)] the spectrum of (3000) stretching overtone band of germane near 6130 cm−1 in which the transition exhibits striking pseudosymmetric‐top structure. A detailed analysis is presented here. The P, Q, and R branches with J up to 10 were assigned, and molecular constants of (3000) state were derived for 74GeH4, 72GeH4, and 70GeH4. The results indicate that the (3000) state of germane is very near the local mode limit and that physically the molecule can be thought of as vibrating with the three GeH stretching quanta localized in one bond. Since there are no strong couplings between this state and any other state, the energy will only be slowly delocalized by the IVR process.