A study of the absolute photoabsorption cross section and the photoionization quantum efficiency of sulphur hexafluoride from the ionization threshold to 420 A

Abstract

The absolute photoabsorption cross section and the photoionization quantum efficiency of sulphur hexafluoride have been measured using a double ion chamber and monochromated synchrotron radiation. The absorption spectrum is unusual because all the prominent features can be associated with transitions into valence states. This behaviour is caused by a barrier in the molecular potential which leads to a suppression of Rydberg structure and an enhancement of intervalence features. The photoionization quantum efficiency reaches a value close to unity for wavelengths shorter than 600 AA, thus resolving an earlier anomaly. Although the Rydberg structure is weak, and superimposed upon a strong background, excitation into these states produces a noticeable effect on the photoionization quantum efficiency. A sum rule analysis has been carried out by combining the present absolute photoabsorption cross section with similar data covering the remaining wavelength regions.

Interchannel coupling effects in the valence photoionization of SF6

“…section measurements 50 have identified a peak assigned to the intervalence transition 1t 2g → 6t 1u at ∼15.5 eV. The origin of this resonance was considered to be due to an electrostatic barrier in the effective molecular potential.…”

“…This conclusion has been generally accepted in recent experimental and theoretical studies. 41,50,51 Photoionization of the 1t 2g subshell is considered next in Fig. 6.…”

“…From the comparison of available experimental and present theoretical results, we confirm that the following valence ordering is most probable: 4t 1u 6 1t 2g 6 3e g 4 (5t 1u 6 +1t 2u 6 ) 1t 1g 6 , which is the widely accepted valence configuration in recent experimental and theoretical studies. 41,50,51 The paper is organized as follows: Sec. II briefly discusses the theoretical methods employed, Sec.…”

Towards a fully kinetic 3D electromagnetic particle-in-cell model of streamer formation and dynamics in high-pressure electronegative gases

“…For low photon energies, scattering is essentially negligible and the only significant process is photo-absorption by which a photon is absorbed by a neutral, which then either forms an electron-ion pair or dissociates. [46][47][48] In the absence of photo-absorption events, the photon is assumed to merely propagate through the gas at the speed of light. The total photo-absorption coefficient, l a , for SF 6 is shown in Fig.…”

Vacuum Ultraviolet Negative Photoion Spectroscopy of SF6, CF4 and SF5CF3

“…It is at this energy, where appropriate, where cross section and quantum yield measurements are taken e Quantum yields for anion production, obtained by dividing cross sections for anions (column 4) by total photoabsorption cross sections. The latter values are given for SF 6 [28], CF 4 [3] and SF 5 CF 3 [20] f Normalisation of the signal strength to determine an effective cross section is not possible because of the non-linear dependence of signal with pressure g Quantum yield cannot be determined because the cross section is not defined relative signal strengths between the bands at 19.9 eV was observed. It is noted that the cross section for non-dissociative electron attachment to SF 6 peaks at very low energy characteristic of s-wave capture [25], but SF 6 -anions observed from reaction (3.2) will arise from all electrons integrated under the cross section vs electron energy distribution.…”