Knowledge Bank

The vibrational harmonic frequencies of these molecules have been estimated from the observed anharmonic frequencies by aid of the method proposed by $us1$ to compute the harmonic frequencies of $A1$ vibrations of $H2O,D2O,H2S,H2Se$ and $D2Se$. This method utilizes the Wilson's splitting of the high frequency from the low in his G matrix for vibration calculation, combined with the Dennison's isotopic rule which states that the anharmonic correction is proportional to the harmonic frequency. The obtained values for $\nu 1$ vibrations are as follows (in $cm-1$): $NH33466.29ND32487.79PH32471PD31771AsH32202.3AsD31567.2SbH31981.7SbD31407.1$ These values as well as those for $\nu 2,v3$, and $v4$ vibrations have been examined in comparison with the older values obtained by other methods. Finally, a dependence of the anharmonicity upon the effective nuclear charge for the valence electron of the central atom has been considered.