The double photoionization/fragmentation of CF₄in the threshold region (35-80 eV)

Abstract

The ~~~l ~i c o t e e h n i q u e has been used in conjunction with a source ofcontinuum (synchrotron radiation) in order to determine the thresholds for fragmentation o f CF, into CF:+F+ (37.6eV). CF:+Ft(42.4eV), C F + + F + (47.5eV) and Ci+Ft(62.0eV).These thresholds are tentatively correlated with specific double-hole states of CF,.

Dissociative photoionization of CF4 from 23 to 120 eV

“…34,35͒ experiments. Among these experiments, Codling et al 35 determined the thresholds for the ion-pair formation of CF 4 2ϩ into F ϩ ϩCF 3 ϩ ͑37.6 eV͒, F ϩ ϩCF 2 ϩ ͑42.4 eV͒, F ϩ ϩCF ϩ ͑47.5 eV͒, and C ϩ ϩF ϩ ͑62.0 eV͒ and tentatively correlated these thresholds with specific two-hole states of CF 4 calculated by Lurkins and Tulea. 36 In this paper, ion branching ratios and absolute partial photoionization cross sections for the dissociative ionization of CF 4 are presented in the energy region 23-120 eV.…”

Unambiguous observation of F-atom core-hole localization in CF4 through body-frame photoelectron angular distributions

“…The contribution to that peak at ∼5 eV is coincidentally at the KER for fragmentation of CF 4 2+ into CF 3 + and F + in their ground states formed by direct double photoionization [25]. However, the threshold for double ionization is 38 eV [25], which is somewhat lower than the lowest state populated by the Auger decay of CF 4 + (1s −1 ) which occurs at 44 eV [14]. The higher KER peak at 7.5 eV [26] is probably coming from a higher lying state which is directly dissociating, e.g., a dication state with an electron removed from one of the bonding C-F σ orbitals, for which earlier calculations indicate there are many candidates in this energy range [27].…”

“…3 can be resolved into at least two contributions with different KER values. The contribution to that peak at ∼5 eV is coincidentally at the KER for fragmentation of CF 4 2+ into CF 3 + and F + in their ground states formed by direct double photoionization [25]. However, the threshold for double ionization is 38 eV [25], which is somewhat lower than the lowest state populated by the Auger decay of CF 4 + (1s −1 ) which occurs at 44 eV [14].…”

Deep core ionic photofragmentation of the CF2Cl2 molecule

“…Whenever the hole is created in an outer valence orbital, this decay process gives rise to a molecular ion plus neutrals [24]. Then again, whenever the hole is created in an inner valence orbital, an atomic ion or ion pairs are produced [25]. The relative intensities of the peaks change with the photon energy over the observed energy range.…”