Spectral Assignments And Analysis Of The Ground State Of Nitromethane In High-resolution Ftir Synchrotron Spectra

The Fourier Transform infrared spectra of CH$_{3}$NO$_{2}$, have been recorded, in the 400-950 \wn spectral region, at a resolution of 0.00096 \wn, using the Far-Infrared Beamline at Canadian Light Source. The observed spectra contain four fundamental vibrations: the NO$_{2}$ in-plane rock (475.2 \wn), the NO$_{2}$ out-of-plane rock (604.9 \wn), the NO$_{2}$ symmetric bend (657.1 \wn), and the CN-stretch (917.2 \wn). For the lowest torsional state of CN-stretch and NO$_{2}$ in-plane rock, transitions involving quantum numbers, {\it$m''$} = 0; {\it$J''$} {$\leq$ $50$} and {\it$K$}${_a}$$^{''}$ {$\leq$ $10$}, have been assigned with the aid of an automated ground state combination difference program together with a traditional Loomis Wood approach\footnote{C.~F.~Neese., \textit{An Interactive Loomis-Wood Package, V2.0,} {\textbf{56$^{th}$}},OSU Interanational Symposium on Molecular Spectroscopy (2001).}. Ground state combination differences derived from more than 2100 infrared transitions have been fit with the six-fold torsion-rotation program developed by Ilyushin et.al\footnote{V.~V.~Ilyushin, Z.~Kisiel, L.~Pszczolkowski, H.~Mader, and J.~T.~Hougen, \textit{J.~Mol.~Spectrosc.} \underline{\textbf{259}},~26, (2010).}. Additional sextic and octic centrifugal distortion parameters are derived for the ground vibrational state