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X-ray Transient Absorption Spectroscopy (XTAS) and theoretical calculations are used to study CCl 4 + prepared by 800 nm strong-field ionization. XTAS simultaneously probes atoms at the carbon K-edge (280–300 eV) and chlorine L-edge (195–220 eV). Comparison of experiment to X-ray spectra computed by orbital-optimized density functional theory (OO-DFT) indicates that after ionization, CCl 4 + undergoes symmetry breaking driven by Jahn–Teller distortion away from the initial tetrahedral structure (T d ) in 6 ± 2 fs. The resultant symmetry-broken covalently bonded form subsequently separates to a noncovalently bound complex between CCl 3 + and Cl over 90 ± 10 fs, which is again predicted by theory. Finally, after more than 800 fs, L-edge signals for atomic Cl are observed, indicating dissociation to free CCl 3 + and Cl. The results for Jahn–Teller distortion to the symmetry-broken form of CCl 4 + and formation of the Cl–CCl+3 complex characterize previously unobserved new species along the route to dissociation.
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This content will become publicly available on August 18, 2026
Instability of the Octahedral Symmetry in Si8O12H8 and Ge8O12H8: A Consequence of the Pseudo-Jahn–Teller Effect
Abstract The symmetry breaking in octahedral silsesquioxane and its germanium analogues (Si8O12H8and Ge8O12H8) has been investigated using the M06-2X/6-31++G(3df, 3pd) method and group theory. Both structures undergo$${O}_{h}\downarrow {T}_{h}$$symmetry breaking, characterized by pseudo-Jahn−Teller stabilization energies of 0.22 kcal/mol for Si-POSS and 9.82 kcal/mol for Ge-POSS. Under the influence of the pseudo-Jahn–Teller effect, the distortion vector involves the vibrational a2gmode with imaginary frequency. The distortion forces in Oh-POSS are predominantly localized on the oxygen atoms and driven by the coupling between the lowest unoccupied molecular orbital (a1g) and the highest occupied molecular orbital (a2g). The symmetry breaking is attributed to a pseudo-Jahn–Teller mechanism of type (a2gx a1g) = a2g. The symmetrical substitution of oxygen atoms by X (where X = C, N, P) results in viable Th-Si8X12H8and Th-Ge8X12H8structures. The observed pseudo-Jahn–Teller distortion and substitutional symmetry breaking caused by X indicates a consistent electronic relaxation mechanism, characterized by the formation of C=C, N=N and P=P bonds on the POSS cubic faces, which serves as hallmarks of stability. Additionally, we find that the volume of substituted Th-symmetrical POSS is sufficiently large to accommodate small ions.
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- Award ID(s):
- 2320718
- PAR ID:
- 10634268
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Journal of Inorganic and Organometallic Polymers and Materials
- ISSN:
- 1574-1443
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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