Knowledge Bank

The $\nu 3$ AND $2\nu 3$ IR bands of natural $GeH4$ have been recorded at resolution between 0.015-0.025 $cm-1$. The spectral components of all five Ge isotopes are clearly resolved for low J values in both bands. At higher J the tetrahedral splittings cause the components of each isotope to overlap and make assignments difficult. Work with pure isotopic germanes is planned. Two interesting phenomena were found. Lines were observed between the main J transitions many years ago by other workers. They are resolved now and may possibly arise from transitions to the IR forbidden $\nu 1$ level because of a high-order resonance with $\nu 3$. The difference between the band origins is less than 1 $cm-1$. Secondly, the absolute intensities of the isotopic components of R(0) and R(1) of both bands have been measured. It has been found that for the $2\nu 3$ band the ratios are in agreement with those expected from the natural abundances of Ge isotopes. The ratios for the $\nu 3$ band are greatly different. Again we attribute this to the possible interaction with $\nu 1$.