Knowledge Bank

Recent broadband measurements of the rotational spectrum of $n$-propanol up to 375 GHz resulted in determination of precise spectroscopic constants for the $Gt$ conformer of this molecule.}, 428 (2006)} This is most likely the most stable conformer, although four other conformers are predicted to be very similar in energy. Assignment of some of these in cm-wave rotational spectra has previously been reported, but it was not possible to extend that work directly to mm-wave spectra. \vspace{0.2cm} Application of graphical Loomis-Wood techniques built into AABS}, 231 (2005)} and CAAARS}, 229 (2005)} spectral analysis packages eventually allowed successful assignment of the remaining four conformers: $Gg$, $Gg\prime$, $Tt$, and $Tg$ $n$-propanol. It was realised that rotational energies in ($Gg$, $Gg\prime$) and ($Tt$, $Tg$) pairs of conformers are highly coupled, but also amenable to description in terms of the Coriolis interaction mechanism. This allowed very precise determination of some energy level differences, such as $\Delta E(Gg\prime -Gg)=3.035046(7)$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. The assignment was checked against $abinitio$ calculations, and is supported by new, precise determinations of dipole moments of some conformers, which were carried out using supersonic expansion cavity-FTMW spectroscopy.