Knowledge Bank

The structures and optical spectroscopy of the $CHF2$ radical and cation were studied by initio molecular orbital calculations and by experiment. Ab initio calculations at the MP2/6-31G$\mathrm{<mrow\; data-mjx-texclass="ORD">\ast \ast </mrow>}$ theory level found that the optimum structure of the $X¯$ $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A1CHF2+$ cation belongs to the $C2\nu$, point group with $r(C-F)=1.2424$ {\AA},$r(C-H)=1.0883$ {\AA} and $\angle F-C-F=119.19\circ$.The optimized structure of the ground state $CHF2(X¯2A\prime$ radical belongs to the C point group with $r(C-F)=1.3360$ {\AA}, $r(C-H)=1.0883$ {\AA} $\angle F-C-F=111.51\circ$ and $\angle H-C-F=113.65\circ$ The ab initio angle between the F-C-F plane and the C-H bond is $\Phi \pi =44.53\circ$. Vibrational frequencies for each $CHF2$ species were computed. The electronic spectra of $CHF2$ and $CDF2$ radicals were observed between 330-430 nm using mass resolved resonance enhanced multiphoton ionization (REMPI) spectroscopy. These spectra arose from two-photon resonances with planar Rydberg states. A third laser photon ionized the radicals. Spectroscopic constants were found for the $F¯(3p)$ Rydberg state of the $CHF1$ radical ($\nu \infty =49312(10)cm-1$, $\nu 2\prime (C-FStr)=1358(15)cm-1$, $\nu 31(CF2scissors)=680(20)cm-1$, $\nu 41(OPLA)=1022(8)cm-1)$ and of the $CDF2$ radical $(\nu \infty =49323(10)cm-1$, $\nu 21(C-FStr)=1300(15)cm-1$, $\nu 31(CF1scissors)=650(15)$ $cm-1$, $\nu 41(OPLA)=864(13)$ $cm-1)$. The REMPI spectra exhibited $\nu 4-=1-5$ hot bands of the $X¯2A\prime$ radical. Modeling of these hot bands with a quartic double-well potential gives the inversion barrier, $BIN=2800(500)cm-1$, and $\Phi m=49(6)\circ$.