High-resolution infrared spectroscopy of 2-fluoroethanol in a molecular beam

Abstract

The high resolution infrared spectrum of 2-fluoroethanol (2FE) in a molecular beam was obtained in the region of 2990-2977 cm-1 . This spectral region contains the asymmetric CH stretch of the fluorinated carbon. Excitation of the CH stretch has previously been observed to photochemically isomerize 2FE from the Gg' to the Tt conformation. The high resolution spectrum of this transition provides the information necessary to quantitatively evaluate the amount of vibrational mode-coupling between the asymmetric CH stretch and the torsional reactive coordinate. Minimal amounts of vibrational mode-coupling was observed in the spectrum which is consistent with the slow photoisomerization rate. The correlation of the amount of mode-coupling and the isomerization rate supports the conclusion that mode-selective vibrational coupling plays an important role in the photochemical dynamics. It is further suggested that the strong intramolecular attractive interactions limit the magnitude of the vibrational mode-coupling.

High-resolution infrared spectroscopy of formamide and deuterated formamide in a molecular beam

“…The experimental apparak,>' has been described in detail elsewhere 22 . Briefly, the molecular beam was created by expanding a mixture of formamide and helium through a 50 gtm n0771e.…”

High resolution infrared spectroscopy of cyclobutane: A study of vibrational mode coupling involving large amplitude, low frequency modes

“…In most previous work, the low frequenc;', large amplitude motion involved torsional motion.s, 6 ,10l,1,1 4 .1s In our previous work on substituted ethanes, we suggested that intramolecular interactions that effect torsional modes, can enhance mode coupling between states involving those torsional modes. 5 ,6, 14 , 15 As noted above, one can view ring puckering in cyclobutane as an extremely hindered torsion, in which the barrier to internal rotation about any C-C bond is essentiai.,. respectively, the K structure is resolved and the weak intensities of these bands prevent us from identifying peak fractionation.…”

“…The experimental apparatus has been described in detail elsewhere. 5 Briefly, the molecular beam was created by expanding a mixture of cyclobutane and helium through a 50 gm nozzle.…”

“…For example, unexpected couplings occur between high frequency hydrogen stretching modes and large amplitude, low frequency modes, such as torsions. 5,6 , 10 ,11, 14 , 1 5 We seek to gain a better understanding of this coupling between disparate modes. Cyclobutane was chosen for this study of vibrational mode coupling because it is a mid-sized organic molecule with interesting structural characteristics and a large amplitude, low frequency mode.…”

Rotational spectrum of a dark state in 2-fluoroethanol using microwave/radio-frequency-infrared multiple resonance

“…In the gas phase, excitation of the asymmetric C-H stretch of 2-fluoroethanol [14] does not show conclusive evidence for coupling to other conformers. Evidence for conformation coupling in the gas phase is difficult to obtain since the geometries and thus the rotational constants of the conformers can differ dramatically.…”