Knowledge Bank

“The intensities of the absorotion bands in the 1700 {\AA} system of $HgCl2$ were determined from photomultiplier recordings. Wavelength measurements of the sharp violet edges were obtained from photographs at a dispersion of 4.2 {\AA}/mm. The hydrogen continuum was used as background with the photomultiplier and the xenon continuum was used for the. An analysis of the system gives the following vibrational constants: The $\nu 3″$ value was obtained from infrared $data1$. Ten bands were used in determining these stants. The positions of sixteen other bands were calculated and their average difference from the measured positions is $5.5cm-1$. Since $\nu 3\prime$ is smaller than $\nu 1\prime$ it appears that the potential function for the antisymmetric stretching mode is not harmonic it may be a double minimum with a small barrier. In contrast to the interpretation of $Wehrli2$ and Sponer aid $Teller3$, no hands have been assigned to the bending frequency, $\nu 2$. Using two bands, a Franck-Condon calculation gives an equilibrium Hg-Cl bond length change of 0.039 - 0.003 {\AA} between the ground and the excited state. Since the bands degrade to the red and since $\nu 1\prime$ is smaller than $\nu 1″$, the bond length must be greater in the excited state. Franck-Condon calculations give intensities for all other bands which are in good agreement with observed. A second system of seven diffuse bands has also been observed near 1500 {\AA}.”