THE ELECTRONIC SPECTRUM OF THE CCl3CCl_{3} RADICAL

Author Institution: Chemical Kinetics Division, Center for Chemical Technology National Institute of Standards and Technology; Chemical Kinetics Division, Center for Chemical Technology; Department of Chemistry, University of Minnesota at Duluth; Department of Environmental Chemistry and Biology, Johns Hopkins University School of Hygiene and Public HealthThe electronic spectrum of $C^{35}Cl_{3}$ radicals was observed between 336-440 ni using mass resolved resonance enhanced multiphoton ionization (REMPI) spectroscopy. This spectrum arose from two-photon resonances with planar Rydberg states. A third laser photon ionized the radicals. One Rydberg series of quantum defect $\delta= 0.545$ is comprised of the $\bar{E} 2_{E^{\prime}}$ (3p) state $(\nu_{0-0}=47170, w_{1}(a^{\prime}_{1}$ sym scr) = 544(6), $\omega^{\prime}_{2}(a_{2}^{\prime\prime}$ OPLA) = 509(21), spin-orbit splitting = $33(5) cm^{-1}$) and the $\tilde{K} ^{2}_{E^{\prime}} (4p)$ state $(\nu_{0-0}= 56236, \omega_{2}^{\prime}= 526(16) cm^{1})$. A second Rydberg series of $\delta =0,50$ is comprised of the $\bar{F} (3d) (\nu_{0-0})=51218 cm^{-1}, \omega_{2}^{\prime}=520(17) cm^{-1}$ and $\bar{M} (4d) (\nu_{0-0}= 57733 cm^{-1}, \omega_{2}^{\prime}= 542(16) cm^{1})$ states. A fit of the Rydberg formuls to these series found the adiabatic ionization potential of the $CCl_{3}$ radical to be $1P_{n}=B.109(5) eV$. The $\bar{J} ^{2}A_{2}^{\prime}(4s)$ Rydberg state $(\nu_{0-0}= 53471, \omega_{2}^{\prime}= 530(20) cm^{1})$ was also observed. The REMPI spectrum exhibited the $v_{2}^{\prime\prime}=1-4$ vibrational hot bands of the $\tilde{X} ^{2}A_{1} (C_{3v})$ radical. Modeling of these hot bands derived the inversion barrier, $B_{i n v} = 460 \pm 40 cm^{-1}

MULTIPHOTON IONIZATION SPECTROSCOPY OF DIFLUOROMETHYL RADICALS

Author Institution: Chemical Kinetics and Thermodynamics Division, National Institute of Standards and Technology; Department of Environmental Chemistry and Biology, Johns Hopkins University School of Hygiene and Public HealthThe structures and optical spectroscopy of the $CHF_{2}$ radical and cation were studied by initio molecular orbital calculations and by experiment. Ab initio calculations at the MP2/6-31G$^{**}$ theory level found that the optimum structure of the $\bar{X}$ $^{1}A_{1} CHF^{+}_{2}$ cation belongs to the $C_{2\nu}$, 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 $CHF_{2}(\bar{X}^{2}A^{\prime}$ 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 $CHF_{2}$ species were computed. The electronic spectra of $CHF_{2}$ and $CDF_{2}$ 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 $\bar{F} (3p)$ Rydberg state of the $CHF_{1}$ radical ($\nu_{\infty} = 49312(10) cm^{-1}$, $\nu_{2}^{\prime} (C-F Str) = 1358(15) cm^{-1}$, $\nu^{1}_{3} (CF_{2} scissors) = 680(20) cm^{-1}$, $\nu_{4}^{1} (OPLA) = 1022(8) cm^{-1})$ and of the $CDF_{2}$ radical $(\nu_{\infty} = 49323(10) cm^{-1}$, $\nu_{2}^{1} (C-F Str) = 1300(15) cm^{-1}$, $\nu^{1}_{3} (CF_{1} scissors) = 650(15)$ $cm^{-1}$, $\nu_{4}^{1} (OPLA) = 864(13)$ $cm^{-1})$. The REMPI spectra exhibited $\nu^{-}_{4} = 1-5$ hot bands of the $\bar{X} ^{2}{A^{\prime}}$ radical. Modeling of these hot bands with a quartic double-well potential gives the inversion barrier, $B_{IN} = 2800(500) cm^{-1}$, and $\Phi_{m} = 49(6)^{\circ}$