Knowledge Bank

The ground state spectra and structures of five-membered ring molecules like pyrrole, furan and thiophene are well established via microwave spectroscopy. Some rotationally-resolved studies of the vibrational bands of these molecules have previously been conducted at high resolution by Fourier transform and infrared diode laser spectroscopy; however, the data obtained via Fourier transform spectroscopy suffers in quality due to the low light flux of conventional light sources (particularly at frequencies lower than 600 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$), and due to the requirement that the entrance iris be very small to obtain spectra at high resolution. We report new rotationally-resolved vibrational spectra of five-membered ring molecules using the intense, spatially-confined infrared light produced by the Canadian Light Source synchrotron, which we have coupled into a Bruker IFS125 Fourier transform spectrometer. Spectra of exceptionally high quality were taken at the full resolution of the instrument (0.001 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$), both with the synchrotron source (400-700 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$) and the internal globar source (700-1000 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$). Comparisons of the 400-700 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ spectra with those taken with a conventional globar source are given, and analysis of the rotational structure of these bands is presented.