POTENTIAL ENERGY CONSTANTS AND CORIOLIS COUPLING COEFFICIENTS FOR FORMALDEHYDE.

$$\begin{array}{ll}K_{C=O}&=12.98\,\,md/{\AA}\\ K_{CH}&=5.072\,\,md/{\AA}\\H_{a}&=1.017\,\,md.\,{\AA}\\H_{\beta}&=1.869\,\,md.\,{\AA}\\H\,\,(out\, of\, plane)&=0.410\,\,md.{\AA}\\k_{CH.CH}&=0.0\quad md./{\AA}\\k_{CH.CO}&=1.014\,\,md./{\AA}\\h_{CH, a}&=-0.284\,\,md.\\h_{CO, a}&=-0.676\,\,md.\\h_{CH, \beta}&=-0.128\,\,md.\end{array}$$ In addition, $\zeta_{3,_6}$ was calculated to be $0.52_{4}$, compared with 0.54 found by Blau and $Nielsen^{3}$ for $H_{2}CO$. Calculations are in progress on refining these values further.Author Institution: Department of Chemistry, Texas A\&M UniversityNormal coordinate calculations were carried out using an IBM 7094 digital computer. The frequencies of $H_{2}CO, D_{2}CO$, and HDCO, corrected for anharmonicity by the method of $Curtis,^{1}$ were sued to fit the force constants. Several constrained force fields were tried and the criteria of ``goodness of fit'' to both the frequency data and known Coriolis coupling coefficients were used to determine the most realistic set of force constants. The constraints on the force field will be discussed and the Coriolis coupling coefficients calculated from the force constants will be given, along with the mean square amplitudes. Of the two internal coordinate sets used, the one which followed the nomenclature of Crawford, $et al,^{2}$ for ethylene gave values for the force constants comparable with those found for ethylene. The force constants were: ""[FIGURE]"