High Resolution IR-Spectra of Furane and Thiophene

Abstract

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 ^-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 amuÄ 2 in the ground state and « -0.2 amuÄ 2 in the excited state for both furane and thiophene.

Ab initio and matrix isolation study of the acetylene–furan dimer

“…Detailed studies of the gas phase spectra of the furan monomer were performed by Mellouki et al [72][73][74] and Pankoke et al [75]. As expected, the frequencies measured in solid argon are slightly red shifted, by 0.5-3 cm À1 compared to the gas phase data.…”

The high-resolution infrared spectrum of thiophene between 600 and 1200cm−1: A spectroscopic and theoretical study of the fundamental bands ν6, ν7, ν13, and the c-Coriolis interacting dyad ν5, ν19

“…The ground state constants of Pankoke et al [7] are summarized in Table 4 for comparison with our results in I r representation. The rotational constants are slightly better determined in [7], and for B and C the agreement is good.…”

“…However, for m 19 which is the only b-type band analysed in the present study the low-K c high-J GSCDs are included since they supply valuable information on asymmetry splitting in the ground state which is not available from a-type bands. Both bands m 7 and m 13 are well resolved and easily assigned; hence we initiated our GSCD analysis from these bands, iteratively extending the assignment and simultaneously refining the previous ground state constants of Pankoke et al [7].…”

“…The constants obtained from the combined fit are given in Table 4. In order to allow direct comparison with the previous ground state parameters [7] and with our theoretical study, the constants are quoted both in III r and I r representation. For the infrared GSCDs the standard deviation of fit is 0.88 · 10 À3 cm À1 , and no residual has a numerical value exceeding 2.00 · 10 À3 cm À1 .…”

“…To our knowledge the only high-resolution study of thiophene reported in the literature is the investigation of the m 13 band at 712.1 cm À1 in 1994 by Pankoke et al [7]. From Doppler-limited diode-laser spectroscopy and high-resolution FTIR spectroscopy the rotational and centrifugal distortion constants for the ground state and the m 13 level were obtained using the Watson Hamiltonian [7].…”