VIBRATIONAL POTENTIAL FUNCTIONS AND ASSIGNMENTS FOR $C_{2}F_{4}$, $C_{2}Cl_{4}$, AND $C_{2}Br_{4}^{*}$

$^{*}$This work was supported in part by the Office of Navel Research.Author Institution: National Bureau of StandardsA modified Urey-Bradley type of force field has been used as the basis for the determination of satisfactory and consistent potential constants for $C_{2}F_{4}$, $C_{2}Cl_{4}$, and $C_{2}Br_{4}$. These force constants were obtained by the joint application of least-squares and high-speed digital computation methods. The frequency fit for these three molecules is generally quite good. In the course of this work it became possible to revise existing assignments for $C_{2}Cl_{4}$, and $C_{2}Br_{4}$, and to adduce evidence which strongly suggests that all the fundamentals have now been correctly located