Knowledge Bank

With the recent improvements for chirped pulse FTMW (CP-FTMW) spectroscopy between 2-18 GHz, substitution structures of molecules and clusters with more than 10 heavy atoms are becoming routine. While previous CP-FTMW results for phenol dimer reported at this conference by Steber et al. necessitated reduced-band measurements in order to achieve the sensitivity to detect the carbon isotopologues, the latest improvements for the 2-8 GHz arrangement have enabled full band detection of all 12 $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C and 2 $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}$O isotopologues of phenol dimer in natural abundance, with improved fits for all detected species. In addition, the added sensitivity of this new 2-8 GHz configuration has enabled a full carbon substitution structure of phenol trimer. The experimental structure of phenol trimer, in agreement with the M06-2X/6-311++g(d,p) \textit{ab initio} structure, is a C$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ oblate symmetric top with 21 heavy atoms; however, all possible isotopic substitutions are off-symmetry axis, so the resulting detected isotopologues have been fit as c-type prolate asymmetric tops. Use of Kraitchman$\prime$s equations for structural determination of a symmetric top molecule require some assumptions from the \textit{ab initio} structure for the complete r structure of the trimer. A detailed summary of these methods, as well as the microwave results for both species, will be presented.