Angle-resolved photoelectron cross section of CF4

Abstract

An angleresolving photoelectron spectrometer for the simultaneous measurement of cross sections and asymmetry parameters using synchrotron radiation Rev.Partial photoelectron cross sections 0' and angular distribution parameters {3 were obtained for the first five valence orbitals in CF 4 : It l , 4t 2 , Ie, 3t 2 , and 40 1 , asa function of photon energy from 17 to 70 eV. These data were taken with the aid of angle-resolved photoelectron spectroscopy and synchrotron radiation. The results were compared with earlier data on CCI 4 • Substantial differences were found. These are explained partly in terms of the absence of a Cooper minimum with a fluorine compound as opposed to the presence of a Cooper minimum with chlorine compounds and partly in terms of the position of shape resonances. Data on CF 4 were also compared with recent calculations of Stephens et al., who used the multiple-scattering Xa method. Structure in the photoelectron spectrum of CF 4 lying on the low energy side of the third band was identified as due to autoionization and evidence is given as to its specific nature.

An (e, 2e+ ion) study of electron-impact ionization and fragmentation of tetrafluoromethane at low energies

“…The peak observed at 22.12 eV is due to the ionization of the orbital 3t 2 and partly due to autoionization states [12,15,62]. Interestingly the peak intensity relative to the main peak at 17.4 eV changes with the projectile energy.…”

“…+ (1e −1 ) ion must be excited or autoionization states 3t 2 −1 nl are populated with energies converging to the CF 4 + (3t 2 −1 ) state. Autoionizing states in this energy region have been observed before in a photoionization study [12]. For the moment, we label this contribution to the 1e orbital.…”

“…In this experiment, the ionic fragments of CF 3 + , CF 2 + , CF + , F + and C + from CF 4 are clearly resolved. We compare our results with electron impact ionization [33,36,47,48,53], and photoionization studies [8,[11][12][13]15,21,22,59]. …”

“…Studies of photon induced reactions include fluorescence measurements [6], photoabsorption [7], photoelectron spectrometry a e-mail: alexander.dorn@mpi-hd.mpg.de [8][9][10][11][12][13][14], threshold photoelectron spectroscopy (TPES) [15][16][17][18], photoion detection [19,20] and various coincidence methods like photoelectron-photoion coincidences (PEPICO) [21][22][23][24], threshold photoelectron-photoion coincidences (TPEPICO) [4,25,26] and threshold photoelectron-fluorescence coincidences (TPEFCO) [5]. Photo double ionization was studied using photoion-photoion coincidences (PIPICO) [27][28][29], photoelectron-photoelectron coincidences (PEPECO) [30] and threshold photoelectron-photoion-photoion coincidences after core ionization (TPEPIPICO) [31].…”

Resonance signatures in the body-frame valence photoionization of CF4

“…Using angle resolved photoelectron spectroscopy and synchrotron radiation, Carlson et al 20 published partial cross sections and asymmetry parameters for valence photoionization of CF 4 . Similar measurements were published a year later by Yates et al 21 .…”