Absolute ionization and dissociation cross sections of tetrahydrofuran: Fragmentation-ion production mechanisms

Abstract

We report an experimental and theoretical investigation on the absolute ionization and fragmentation cross sections of tetrahydrofuran (THF, C4H8O), a base molecule of the DNA-backbone. The measurements enabled the identification of 50 ionic species produced by 12 eV up to 2000 eV electron impact which allowed us to make a close inspection of the mechanisms of both the primary vacancy production and the postcollisional fragmentation pathways which lead to the fragment ions. The experimental cross sections of the ionic species were examined in the framework of the fragmentation matrix model to attribute from which molecular orbitals (MOs) the electron is removed and find out the relative contribution of up to 15 outer and inner valence MOs in the fragment-ion production. A comparison between measured and calculated dissociative cross sections relative to the molecular parent ion cross section allowed us to clearly identify the prevalence of the single or double ionization in the fragment-ion production. Due to these different production mechanisms, the relative proportion of some ejected fragment-ions strongly depends on the impact energy. The single ionization of the MOs leading to selected fragment ions was compared to those measured at a low electron-impact energy using a reaction microscope with good agreement between the two techniques. The formation of the dications C4HnO2+, excluding the molecular parent dication, is also presented.

Ionization of biological molecules by multicharged ions using the stoichiometric model

“…6b seems to corroborate the new scaling. We also included the electron impact ionization measurements with equivelocity conversion on pyrimidine [24] and THF [24,26,27]. It will be interesting to crosscheck with future experiments, mainly for higher projectile charge states.…”

“…The comparison with the experimental data available shows . Experiments: proton impact on ○ adenine [15], △ uracil [19], ▽ pyrimidine [23] and THF [25]; electron impact on ⊳ pyrimidine [24], and ⊲, [26,27] THF. C2H7N, CH5N, methane and ammonia [28], ☀ ammonia and H2 [29], and • water [30].…”

A complete data set for the simulation of electron transport through gaseous tetrahydrofuran in the energy range 1–100 $$\hbox {eV}$$

“…For this reason, electron interactions with this benchmark molecule have been widely studied both in experiments and calculations at different levels of theory. As far as crosssection data are concerned, there are available results of total cross sections (TCSs) [8][9][10][11][12][13][14][15], integral elastic cross sections (ICSs) [16][17][18][19][20][21][22][23][24][25][26][27]49], integral vibrational [23][24][25][26][28][29][30] and electronic-state [31][32][33][34][35] excitation cross sections, total ionization cross sections [14,[36][37][38][39][40][41] and integral dissociative electron attachment (DEA) [42][43][44] cross sections. In addition, for most of the processes, differential cross sections (DCSs) [15,26,29,…”

Excitation and ionisation cross-sections in condensed-phase biomaterials by electrons down to very low energy: application to liquid water and genetic building blocks

“…This knowledge is essential for the better understanding, through modelling, of numerous medical and technological applications, including radiation therapy for cancer 8,9 or advanced nanofabrication techniques. 10,11 Plenty of experimental information is available on electronimpact ionisation cross-sections (total probabilities as well as energy spectra of ejected electrons) of relevant biomolecules (such as water or DNA nucleobases), however it is usually limited to the gas phase, [12][13][14][15][16][17] without taking into account the condensed-phase nature of living organisms. Experimental data on electronic excitations are much scarcer and scattered 16,[18][19][20][21] and also limited just to molecules in the gas phase, with only a few exceptions.…”