Intermediate-energy differential and integral cross sections for vibrational excitation in α-tetrahydrofurfuryl alcohol

Abstract

Differential and integral cross section measurements, for incident electron energies in the 20-50 eV range, are reported for excitation of several composite vibrational modes in α-tetrahydrofurfuryl alcohol (THFA). Optimisation and frequency calculations, using GAUSSIAN 09 at the B3LYP/aug-cc-pVDZ level, were also undertaken for the two most abundant conformers of THFA, with results being reported for their respective mode classifications and excitation energies. Those calculations assisted us in the experimental assignments of the composite features observed in our measured energy loss spectra. There are, to the best of our knowledge, no other experimental or theoretical data currently available in the literature against which we can compare the present results.

Intermediate energy electron impact excitation of composite vibrational modes in phenol

“…12). Recently, however, for the biomolecules tetrahydrofuran (THF) 13,14 and tetrahydrofurfuryl alcohol (THFA), 15 it has been demonstrated that the vibrational excitation cross sections persist in magnitude away from the lower-lying shape resonances at a) Author to whom correspondence should be addressed. Electronic mail:…”

Excitation of vibrational quanta in furfural by intermediate-energy electrons

“…In particular we find that at 20 eV, both angular distributions are quasi-isotropic, at 30 eV, there is just a suggestion for their DCS being more forward peaked at the smaller scattered electron angles, while at 40 eV, both angular distributions are now clearly forward peaked in magnitude at smaller θ. The tendency for the angular distributions of composite vibrational modes to be quasi-isotropic, at energies ∼15-20 eV, has been observed by us previously in THF, 5 THFA, 7 pyrimidine, 8 and phenol 11 and still awaits a definitive explanation from theory. The angular distribution results at 40 eV are more understandable in terms of the target molecular properties, in that they exhibit a behaviour consistent with furfural having both a strong permanent dipole moment (3.46-3.57 D 51,52 for the trans conformer), and a dipole polarisability of some magnitude (59.92 a 3 0 53 ).…”

“…We believe this is likely to be the case as structurally similar ring-based species such as THF, 3,6,54 THFA, 7 and even pyrimidine 8 all exhibit similar π * shape resonances in that energy regime. In Fig.…”

“…For instance for some of the composite vibrational modes, 5,7,11 for incident electron energies between 15 and 50 eV, the angular distributions of the cross sections are quasi-isotropic, whereas at those same energies, the elastic angular distributions and the angular distributions for the optically allowed discrete-inelastic electronic states are often strongly peaked in magnitude [20][21][22][23][24][25][26][27][28][29] at the smaller scattered electron angles. That latter behaviour is understood in terms of the strong dipole polarisabilities and permanent dipole moments of the molecules in question.…”

“…Over the last few years, we have been interested in measuring intermediate-energy electron-impact cross sections, often for bands of composite vibrational quanta, in biomolecules such as water (H 2 O), 1,2 tetrahydrofuran (THF), [3][4][5][6] α-tetrahydrofurfuryl alcohol (THFA), 7 and pyrimidine (Py), 8 and for important products from the application of low-temperature plasmas 9,10 on biomass such as phenol 11,12 and furfural (this paper). There are several reasons for this, with one being to contribute to the creation of "complete" cross section data bases for those species.…”