Photoionization mass spectrometry of 1,1-difluoroethane

Fragmentation of valence electronic states of CHF2CF3+ studied by threshold photoelectron–photoion coincidence (TPEPICO) techniques in the photon energy range 12–25 eV

“…From the molecular orbital calculation, it is clear that this state is produced through the loss of a C−C σ-bonding electron. This phenomenon is also observed with other fluorinated ethanes [7,9,27], and is consistent with the argument that fluorine substitution stabilises the C−H bonds more effectively than the C−C bond [27].…”

“…At present both industrial and scientific attention is strongly focused on the HFCs, because the presence of chlorine atoms in HCFCs can still have a deleterious effect on ozone [2]. The growing importance of HFCs has prompted a number of recent studies to determine their physical and chemical properties, as well as to understand their chemical behaviour in the atmosphere [3][4][5][6][7][8]. Even though HFCs do not destroy the ozone layer, they still pose a threat to the environment because of their potential to contribute to global warming.…”

PHOTOELECTRON PHOTOION COINCIDENCE STUDY OF THE FRAGMENTATION OF VALENCE STATES OF CHF2–CH3+ IN THE RANGE 12–25 eV

“…This value is 0.20 eV higher than the calculated AIE of CHF 2 -CH 3 , and 0.16 eV higher than that reported by Heinis et al [7] The former discrepancy shows the limitation of using the TPES to determine the ionization threshold of a molecule that has a large geometry change after ionization, and hence a small Franck-Condon factor at threshold. [22,23] Lifshitz et al [8] have also researched the ionisation process by means of EI ionisation, and they reported an ionisation threshold of 12.68 eV.…”

“…Because of its possible application as refrigerant and its possible effect on global warming, most of the previous researches have concentrated on its thermodynamic property, structure, infrared spectrum and reactions in atmosphere. Only a few early papers have been published which concern the dissociative ionisation and decay mechanism of valence states of CHF 2 -CH 3 using VUV photoionisation method [7][8][9][10][11][12]. In the six reported works, three of them are concerned with the fragmentation by electron impact ionisation (EI).…”

“…Also, the appearance energies determined by electron impact ionisation are normally large than those determined by photoionisation. The only photoionisation (PI) study on the fragmentation of CHF 2 -CH 3 with photoionisation mass spectrometry (PIMS) and threshold photoelectron spectroscopy (TPES) used the hydrogen many-line pseudo-continuum and the helium Hopfield continuum as ionisation radiation sources [7]. The interests of Heinis et al [7] were mainly to determine appearance energies and heats of formation of the fragment cations, although they also observed some isolated-state behaviour of electronic states of the parent cation at photon energies above 16 eV.…”