Knowledge Bank

We have interfaced a newly constructed eleven chamber interferometer, the ETH-SLS Bruker IFS 125 HR prototype 2009, to the infrared port available at the Swiss Light Source (SLS), located at the Paul-Scherrer-Institute. The Maximum Optical Path Difference (MOPD) of this spectrometer is 11.70~m allowing for a best theoretical unapodized resolution of 0.00053~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ (18~MHz). The ETH-SLS Bruker spectrometer is a further development of our nine chamber interferometer Bruker IFS 120/125 Zurich prototype 2001, \textbf{2003}, \emph{84}, 177.}$,$, \textbf{2007}, \emph{8}, 1271.} which has an MOPD of 9.4~m and unapodized resolution of 0.00068~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ (23~MHz). We present spectra of CO and pyrimidine (C$4$H$4$N$2$) as examples to illustrate the improved resolution. Due to the high brightness of the synchrotron source the signal-to-noise ratio is effectively 5 to 20 times better than that of conventional thermal sources in the spectral region between 180 and 900~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ (6-28 THz). We present examples of pyrimidine (C$4$H$4$N$2$) and CDBrClF spectra in the region 600 to 900~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ and of phenol (C$6$H$5$OH) and aniline (C$6$H$5$NH$2$) spectra in the region 180 to 350~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. Due to the excellent resolution and the bright synchrotron source we were able to detect the spin statistical weights in the pyrimidine, \textbf{2007}, \emph{243}, 280.} spectra and found new combination bands in the CDBrClF spectra. We were able to rotationally resolve the torsional $c$-type band of phenol with $\nu 0a=309.1141$~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ and $\nu 0b=309.5517$~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ and detect a torsional splitting of 0.4376~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ in the $v=1$ torsional level. In addition, we were able to rotationally resolve and assign the very weak two torsional $b$-type subbands of aniline with $\nu 0a=234.8$~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ and $\nu 0b=304.3$~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ showing the mode selective inversion splitting, \textbf{1998}, \emph{298}, 320.}.