Fragmentation of Tetrahydrofuran Molecules by H⁺, C⁺, and O⁺ Collisions at the Incident Energy Range of 25–1000 eV

Abstract

We have studied fragmentation processes of the gas-phase tetrahydrofuran (THF) molecules in collisions with the H(+), C(+), and O(+) cations. The collision energies have been varied between 25 and 1000 eV and thus covered a velocity range from 10 to 440 km/s. The following excited neutral fragments of THF have been observed: the atomic hydrogen H(n), n = 4-9, carbon atoms in the 2p3s (1)P1, 2p4p (1)D2, and 2p4p (3)P states and vibrationally and rotationally excited diatomic CH fragments in the A(2)Δ and B(2)Σ(-) states. Fragmentation yields of these excited fragments have been measured as functions of the projectile energy (velocity). Our results show that the fragmentation mechanism depends on the projectile cations and is dominated by electron transfer from tetrahydrofuran molecules to cations. It has been additionally hypothesized that in the C(+)+THF collisions a [C-C4H8O](+) complex is formed prior to dissociation. The possible reaction channels involved in fragmentation of THF under the H(+), C(+), and O(+) cations impact are also discussed.

Interactions of protons with furan molecules studied by collision-induced emission spectroscopy at the incident energy range of 50–1000 eV

“…A detailed technical information was described in references [16,17]. The sketch of the apparatus and methodology of collecting of the data was presented in our previous papers [15,18]. Briefly, the applied set up allowed measurement and identification of the reaction products by detecting their emission and it consisted of a water cooled cation source, magnetic mass selector, collision cell, and an optical spectrometer equipped with sensitive multichannel photon-counting detector [15][16][17][18].…”

“…Also fluorescence spectrum measured in the studies of electron impact excitation of furan [25] presents pronounced intensity of the diatomic CH fragments formed in the A 2 Δ, B 2 Σ − and even C 2 Σ − electronic states and the C 2 fragments in the d 3 Π g excited state. Present results of fragmentation of furan molecule may also be compared to the photon [26][27][28], cation [15] and electron [29,30] impact fragmentation of other five-and six-membered heterocyclic molecules. Again in contrast to present measurement all these studies demonstrated major fragmentation of the target molecules into several different atomic and diatomic fragments.…”

“…The spectra were not corrected for the wavelength dependence of the sensitivity of the detection system. The data for H + +THF collisions was taken from [15].…”

“…Therefore, we have calculated the synthetic CH spectrum utilizing the LIFBASE molecular spectra simulation program [31] with the use of vibrational and rotational constants of the A 2 Δ, B 2 Σ + and X 2 Π r electronic states of CH from [32][33][34][35][36][37]. Similar computer procedure, employed in the analysis of spectra of diatomic molecules, occurring in cation-and photoninduced fragmentation of five-and six-membered heterocycles, has been recently proven to be efficient and dependable [15,18,27,28,38]. Calculations show that in the collisions of furan with the H + (Fig.…”

“…the emission yields have been recorded. For comparison, the emission yields in the H + + tetrahydrofuran collisions have been also remeasured in the 20-1000 eV energy range, but with smaller energy step size than in our previous studies [15]. For both impact systems the highest yields have been observed for production of the excited H atoms which intensities rapidly decrease with increasing principal quantum number n. Moreover, the intensity ratios of the H (n = 4) emissions and the A 2 Δ → X 2 Π r bands of the CH show that the H (n = 4) are more abundant fragments in the entire studied energy range.…”