Infra-Red Bands in the Spectrum of Difluoromethane

Eight absorption bands have been observed in the infra-red spectrum of C${\mathrm{H}}_2$ ${\mathrm{F}}_2$. Seven of these are believed to be fundamental bands and have been identified as follows; the symmetry species of the band being given in parentheses: ${\omega }_1\left(A_1\right)=2949\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, ${\omega }_2\left(A_1\right)=1116\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, ${\omega }_4\left(A_1\right)=528.6\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, ${\omega }_6\left(B_1\right)=3015.2\mathrm{}$, ${\omega }_7\left(B_1\right)=1176.1\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, ${\omega }_8\left(B_2\right)=1089.7\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$ and ${\omega }_9\left(B_2\right)=1435.4\mathrm{}$ ${\mathrm{cm}}^2$. A band of species $B_1$ is observed at 2945 ${\mathrm{cm}}^{-1\mathrm{}}$. It is identified as ${\omega }_5+{\omega }_9$ and from this it is inferred that ${\omega }_5\left(A_2\right)=1510.6\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. Rotational constants for the normal state are found to be $B^{\prime \prime }=0.354\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$ and $C^{\prime \prime }-B^{\prime \prime }=1.303\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. From these values the values $r_0(\mathrm{C}-\mathrm{F})=1.32\mathrm{}$A and ∠(F-C-S)=107° are obtained assuming that $r_0(\mathrm{C}-\mathrm{H})=1.094\mathrm{}$A and ∠(H-C-H)=110°.