INTERNAL ROTATION IN CF$_{3}$I$\cdots$NH$_{3}$ AND CF$_{3}$I$\cdots$N(CH$_{3})_3$ PROBED BY CP-FTMW SPECTROSCOPY
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Date
2011
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Ohio State University
Abstract
The pure rotational spectra of CF$_{3}$I$\cdots$NH$_{3}$ and CF$_{3}$I$\cdots$N(CH$_{3})_3$ have been measured by chirped-pulse, Fourier transform microwave (CP-FTMW) spectroscopy between 7 and 18.5 GHz. Both molecules are generated by supersonic expansion of a gas sample containing a small percentage of each precursor in a balance of argon. The spectra of both complexes are consistent with {\it{C}}$_{3v}$ prolate symmetric top structures. The observed spectrum of CF$_{3}$I$\cdots$NH$_{3}$ displays evidence for internal rotation of NH$_{3}$ about the principal axis. More than one hundred transitions of CF$_{3}$I$\cdots$NH$_{3}$ have been assigned to the internal rotor {\it{A}} state allowing rotational, centrifugal distortion constants and a nuclear quadrupole coupling constant for the iodine atom to be determined for this state. Measurements performed using a Balle-Flygare FTMW spectrometer further allow determination of a nuclear quadrupole coupling constant for the $^{14}$N nucleus. Many transitions in the spectrum of the CF$_{3}$I$\cdots$$^{15}$NH$_{3}$ isotopologue have also been measured and the length of the halogen bond between the iodine and nitrogen atoms has been determined. Measurements of hyperfine components in nine different $J^{\prime\prime}$$\leftarrow$$J^{\prime}$ transitions of CF$_{3}$I$\cdots$N(CH$_{3})_3$ have allowed assignment of the spectrum of this complex to determine rotational, centrifugal distortion and nuclear quadrupole coupling constants.
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Author Institution: School of Chemistry, University of Bristol, Bristol, BS8 1TS, U.K.