Knowledge Bank

We report here a theoretical study of the cluster $effect^{1} $(i.e., the formation of nearly degenerate, four-member groups of rotation-vibration energy levels at higher J and $Ka$ values) in the $H2Te$ molecule. As the initial step of the investigation, we have carried out an {ab initio} calculation of the potential energy surface for the electronic ground state of $H2$Te by means of the CCSD(T) method. With this potential energy surface as input, we have then used the MORBID (Morse Oscillator Rigid Bender Internal Dynamics) $program2$ to calculate the rotation vibration energy spectrum of $H2130Te$ and its isotopomers for $J\le 40$. These calculations reproduce the few known vibrational energies for $H2Te$ and HDTe to within a few $cm-1$. The cluster structures obtained for the vibrational ground state and the fundamental vibrational levels of $H3Te$ are found to be extremely similar to those determined previously for $H2Sc3$. In particular, we do not determine any significant displacement of the clusters towards lower J values relative to $H2Se$. Hence the experimental observation of the cluster states in $H2Te$ will be atleast as difficult as in $H2Se$, for which the cluster effect has been experimentally $verified4$.