High Resolution IR-Spectra of Furane and Thiophene

Abstract

Åbstract The spectra of the out-of-plane fundamental band of furane (C4H4O) centered at 744 cm -1 and of thiophene (C4H4S) at 712 cm -1 were measured in Doppler-limited resolution with a diode-laser spectrometer at Köln and with a high-resolution Fourier transform spectrometer at the University of Gießen. An interactive Loomis-Wood program was applied to identify the c-type transitions of furane and thiophene. The molecular parameters were determined from the observed line positions and the available microwave data by least-squares-fits using Watson's A-reduced Hamiltonian. Some relations among parameters appearing in different formulations of the Hamiltonian are represented explicitly in connection with the derivation of the unreduced constants. The unreduced constants were derived for both molecules using the planarity relations. We determined the inertial defects to be ≈ 0.05 amuÅ 2 in the ground state and ≈ -0.2 amuÅ 2 in the excited state for both furane and thiophene.