X-ray, ultraviolet, and synchrotron radiation excited inner-valence photoelectron spectra of CH4

Abstract

The inner-valence electron states of the methane molecule have been studied by means of x-ray, synchrotron radiation, and UV-photoelectron spectroscopy. Five correlation satellites have been identified and a detailed study has been carried out of the 2a−11 single hole state. For this state a Franck–Condon analysis has been performed, suggesting an equilibrium bond distance of 1.279 Å. The vibrational lines have a Lorentzian shape and the linewidth increases gradually with the vibrational quantum number. This probably indicates a reduction of the lifetime of the vibrational states due to predissociation. A discussion of the potential curves related to the correlation satellites is included.

High-resolution (e, 2e + ion) study of electron-impact ionization and fragmentation of methane

“…They arise due to ionization-excitation satellite states. 11,24 These states usually have repulsive potential curves, thus, high KER up to about 4 eV is observed for this contribution (BE range: 26 eV-31 eV), as can be seen in Fig. 4(c).…”

“…A single peak structure is observed at BE = 13.7 eV for the CH + 4 ion with a line width of about 2.4 eV. 14,24 Compared to the vibrationally resolved spectra of the 1t 2 band, 21,22 the channel at BE = 13.7 eV can be attributed to the ionization to the low-energy vibrational levels of the (1t 2 ) −1 state. The measured kinetic energy distribution of CH + 4 is presented in Fig.…”

“…35,37 The second channel belongs to the peak at BE = 22.8 eV, which corresponds to the ν = 1 and ν = 2 vibrational levels of the (2a 1 ) −1 state. 21,23,24 The KER for this process (BE range: 20 eV-25 eV) is relatively high with a broad distribution up to about 2.5 eV, as shown in Fig. 4(c).…”

“…As the fragment ions are detected in coincidence with the ejected electrons, the measured BE spectra can be used to find out which ionization channels lead to specific products. [21][22][23][24] In the earlier studies, 19,20 however, the fragment ions CH + 3 , CH + 2 , CH + , and C + were not well resolved in the experiment and the BE resolution was not better than 6 eV. Very recently, the experimental setup has been improved in many aspects including the mass resolution and detection efficiency of the fragment ions as well as the BE resolution.…”

Ionization of small molecules induced byH+, He+, andKovács1, Herczku2, Juhász3 et al. 2016Phys. Rev. A

“…and −0.5329 a.u. [46], as well as by occupation numbers 2 and 6, respectively. The doubly differential cross section (DDCS) for the total electron production describing the energy and angular distribution of the electron following the ionization of the molecule is the sum of DDCSs for the electron emission from the individual MOs:…”