15min:
HIGHEST RESOLUTION FOURIER TRANSFORM INFRARED SPECTROSCOPY WITH AN ELEVEN CHAMBER BRUKER INTERFEROMETER AT THE SWISS SYNCHROTRON.

S. ALBERT, K. K. ALBERT, M. QUACK, PHYSICAL CHEMISTRY, ETH ZÜRICH, CH-8093 ZÜRICH, SWITZERLAND; PH. LERCH, L. QUARONI, SWISS LIGHT SOURCE, PAUL-SCHERRER-INSTITUTE, CH-5232 VILLIGEN, SWITZERLAND ; A. KEENS, BRUKER OPTICS, D-76275 ETTLINGEN, GERMANY.

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-1 (18~MHz). The ETH-SLS Bruker spectrometer is a further development of our nine chamber interferometer Bruker IFS 120/125 Zurich prototype 2001\footnoteS. Albert, K.K. Albert and M. Quack, Trends in Optics and Photonics , \textbf2003, 84 , 177.,\footnoteS. Albert and M. Quack, ChemPhysChem , \textbf2007, 8 , 1271. which has an MOPD of 9.4~m and unapodized resolution of 0.00068~cm-1 (23~MHz). We present spectra of CO and pyrimidine (C4H4N2) 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-1 (6-28 THz). We present examples of pyrimidine (C4H4N2) and CDBrClF spectra in the region 600 to 900~cm-1 and of phenol (C6H5OH) and aniline (C6H5NH2) spectra in the region 180 to 350~cm-1. Due to the excellent resolution and the bright synchrotron source we were able to detect the spin statistical weights in the pyrimidine\footnoteS. Albert and M. Quack, J.~Mol.~Spectrosc. , \textbf2007, 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 nu0a=309.1141~cm-1 and nu0b=309.5517~cm-1 and detect a torsional splitting of 0.4376~cm-1 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 nu0a=234.8~cm-1 and nu0b=304.3~cm-1 showing the mode selective inversion splitting\footnoteB. Fehrensen, M. Hippler and M. Quack, Chem. Phys. Lett. , \textbf1998, 298 , 320..