Knowledge Bank

A new technique was used for deriving spectroscopic constants by reference to the known constants of a related electronic state. Applications of this method to several diatomic molecules revealed its usefulness and encouraged its use with the triatomic hydrogen molecules. Spectroscopic $Bo$ constants for Rydberg states of $H3$ and $D3$ are obtained. Predicted and observed $Bo$ values for the upper state of the band are 21.87and 21.96 $cm-1$ respectively.