Deep-core photoabsorption and photofragmentation of tetrachloromethane near the Cl K-edge

Abstract

The fragmentation of the tetrachloromethane molecule following core-shell photoexcitation and photoionization in the neighborhood of the chlorine K-edge has been studied by using time-of-flight mass spectroscopy and monochromatic synchrotron radiation. Branching ratios for ionic dissociation were derived for all the detected ions, which are informative of the decay dynamics and photofragmentation patterns of the core-excited species. In addition, the absorption yield has been measured with a new assignment of the spectral features. The structure that appears above the Cl 1s ionization potential in the photoionization spectrum has been ascribed to the existing connection with electron-CCl scattering through experimental data and calculations for low-energy electron-molecule cross sections. In addition, the production of the doubly ionized Cl fragment, Cl, as a function of the photon energy has been analysed in the terms of a simple and an appealing physical picture, the half-collision model.

Double‐valence photoionization of SUVA134a molecule (CFH2CF3)

“…Full blue line: Thomas' equation. Full black line: KO (Equation [8]). Dashed red line: SO contribution, that is, the difference between the blue line and the black line (KO).…”

“…The KO probability is calculated by fitting the σ 2+ /σ tot ratio at low excess energy using Equation 8. Although the magnitudes of SO and KO do depend on the molecular structure [ 27 and references therein], KO has been described quite simply by either electron impact single ionization of He + [ 4,7,27 and references therein] or Lotz's formula (Equation [8]). 20,22 The SO probability is obtained by deducting the σ 2+ /σ tot from the KO probability.…”

“…multiphoton ionization, which involves both direct and sequential processes. The two electrons in the continuum split, either symmetrically or asymmetrically, and the excess energy ε is given by ε = hν À I P 2+ + ϕ, [1][2][3][4][5][6][7][8][9][10] where ϕ includes rotational and vibrational energies. Thus, photo-double ionization of atoms and molecules depends on the particulars of the initial and final target wave functions.…”

Insights on the site-selective fragmentation of CF2Cl2 and CH2Cl2 at the chlorine K-edge from ab initio calculations

“…3,[26][27][28] In particular, in the case of small halogenated organic compounds, distinct ultrafast fragmentation channels at different edges have been reported during the last few years. 2,8,10,11,13,15,16,22,[29][30][31][32][33][34] The Cl 2p 3/2 → σ * resonance in CH 2 Cl 2 induces ultrafast C-Cl bond cleavage, with atomic and molecular decay as competitive channels, 13,29 whereas selectivity was not obtained for the CCl 4 molecule. 29,31 For the CF 3 Cl molecule, the C1s → σ * resonance leads to the C-Cl bond-breaking, whereas the resonance at Cl 2p exhibits a complex fragmentation mechanism.…”

“…2,8,10,11,13,15,16,22,[29][30][31][32][33][34] The Cl 2p 3/2 → σ * resonance in CH 2 Cl 2 induces ultrafast C-Cl bond cleavage, with atomic and molecular decay as competitive channels, 13,29 whereas selectivity was not obtained for the CCl 4 molecule. 29,31 For the CF 3 Cl molecule, the C1s → σ * resonance leads to the C-Cl bond-breaking, whereas the resonance at Cl 2p exhibits a complex fragmentation mechanism. 35 Carbon atoms in distinct chemical environments can also lead to selective fragmentation.…”