Electronic excitation (5–9 eV) in ethylene and some haloethylenes by threshold electron-impact spectroscopy with an improved energy resolution

Electronic excitations of fluoroethylenes

“…The threshold electronimpact excitation spectra of vinyl fluoride and 1,1difluoroethylene were observed by Verhaart and Brongersma. 5 The UV photoabsorption spectrum and electron energy loss spectra of tetrafluoroethylene have been reported recently by Eden et al 6 They, for the first time, proposed a Rydberg series of nd character. Robin reviewed the electronic spectra of haloethylenes including fluoroethylenes.…”

“…But no excitation at 6.4 eV was found in the study later by Verhaart and Brongersma. 5 They restrained themselves from making any concrete conclusion regarding this due to their low resolution measurements; however, since there was clearly no direct excitation at an energy loss of 6.4 eV for the impact energies between 6.5 and 9.5 eV, they concluded that such an excitation is doubtful. The present study firmly reveals that there is no triplet excitation at 6.4 eV.…”

“…For this purpose, there were many studies in the past, especially experimental ones, on fluoroethylenes. [1][2][3][4][5][6] However, even after many investigations by using UV spectroscopic and electron/ion-impact studies of these gaseous fluoroethylenes, the assignments and properties of the electronic states involved in the transitions are not free from ambiguity. For example, the second triplet state in vinyl fluoride found in an experimental study 4 which is thought to be due to → 3s Rydberg excitation has been proposed to be due to → * valence excitation.…”

“…7,8 However, a study later did not find any such excitation. 5 Only tentative or speculative assignments regarding → * excitations in fluoroethylenes were made in most of the experimental studies but in some other studies no evidence was found for these valence-type excitations.…”

Stimulated radiative recombination of and

“…In particular, for oxide-coated cathodes, the electrons must make their way through the oxide matrix, and in the presence of a magnetic field, with the induced spiralling, it is not inconceivable that electrons with significant transverse velocities are not emitted along the accelerating field axis but rather are absorbed in the matrix. Electron scattering apparatuses employing beams derived from indirectly heated oxide filaments [22] have been found to have superior energy resolution to similar apparatuses with directly heated tungsten filaments [23], even when thick, narrow slits were employed to eliminate electrons with large transverse velocities. This comparison has been discussed further in [24].…”