Knowledge Bank

The 1--0, 2--0, 3--0, 4--0 and 5--0 bands of $HCl35$ and the 1--0 and 2--0 bands of $DCl35$ have been measured with high precision. A critical analysis has been made to determine the rotational and vibrational constants of these molecules. It is necessary to use a polynomial in m of the sixth degree to satisfactorily represent the frequencies of the band lines in the case of the most precisely measured bands. $B0$ for $HCl35$ has been found to have a value of $10.440254\pm 0.000010$ $cm-1.B0$ for $DCl35$ was found to be $5.392261\pm 0.000010$ $cm-1$. When the $B11$ obtained for $DCl36$ is combined with the microwave measurement of $B0$ by Cowan and Gordy the value obtained for the velocity of light $C=299.793.1\pm 0.65$ km/sec. The observed rotational and vibrational constants $(Yij)$ have been used to calculate the potential constants of $HCl36$ making use of Dunham’s theory of a rotation vibrator. It is shown that $HCl35$ is not a pure rotating vibrator since that observed and calculated values of $Y02\sim D$ are in disagreement by about 1 part in 1000 which is approximately 10 times the experimental error. Making use of the molecular constants for $HCl36$ AND $DCl35$ and the accurately known atomic masses it is deduced that the ground level $B0$ is perturbed by the upper electronic levels by 1 part in 8000. The sign of The perturbation is in increase $B0$ over its unperturbed value. The sign of the perturbation is such that it may be presumed the HCl molecule has a positive magnitude moment. It was calculated $\mu j=+0.2$ and + 0.1 nuclear magnetons respectively for $HCl32$ and $DCl35$.