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Beam-spin asymmetry Σ for Σ− hyperon photoproduction off the neutron
- PAR ID:
- 10330720
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Physics Letters B
- Volume:
- 827
- Issue:
- C
- ISSN:
- 0370-2693
- Page Range / eLocation ID:
- 136985
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Conformational effects on the σ‐electron delocalization in oligosilanes are addressed by Hartree–Fock and time‐dependent density functional theory calculations (B3LYP, 6‐311G**) at MP2 optimized geometries of permethylated uniformly helical linear oligosilanes (all‐ω‐SinR2n+2) up ton=16 and for backbone dihedral anglesω=55–180°. The extent of σ delocalization is judged by the partition ratio of the highest occupied molecular orbital and is reflected in the dependence of its shape and energy and of UV absorption spectra onn. The results agree with known spectra of all‐transoidloose‐helix conformers (all‐[±165]‐SinMe2n+2) and reveal a transition atω≈90° from the “σ‐delocalized” limit atω=180° toward and close to the physically non‐realizable “σ‐localized” tight‐helix limitω=0 with entirely different properties. The distinction is also obtained in the Hückel Ladder H and C models of σ delocalization. An easy intuitive way to understand the origin of the two contrasting limits is to first view the linear chain as two subchains with alternating primary and vicinal interactions (σ hyperconjugation), one consisting of the odd and the other of the even σ(SiSi) bonds, and then allow the two subchains to interact by geminal interactions (σ conjugation).more » « less
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Nonagermanide clusters are widely used in inorganic synthesis and are actively studied by experimentalists and theoreticians. However, chemical bonding of such versatile species is still not completely understood. In our work we deciphered a bonding pattern for various experimentally obtained nonagermanide species. We localized the electron density via the AdNDP algorithm for the model structures ([Ge 9 ] 4− , [Ge 9 {P(NH 2 ) 2 } 3 ] − , Cu[Ge 9 {P(NH 2 ) 2 } 3 ] and Cu(NHC)[Ge 9 {P(NH 2 ) 2 } 3 ]) and obtained a simple and chemically intuitive bonding pattern which can explain the variety of active sites and the existence of both D 3h and C 4v geometries for such clusters. Moreover, the [Ge 9 ] 4− core is found to be a unique example of an inorganic Zintl cluster with multiple local σ-aromaticity.more » « less
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The purpose of this article is to give new constructions of linear orders which are minimal with respect to being non-σ-scattered. Specifically, we will show that Jensen's diamond principle implies that there is a minimal Countryman line, answering a question of Baumgartner. We also produce the first consistent examples of minimal non-sigma-scattered linear orders of cardinality greater than aleph1, as given a successor cardinal kappa+, we obtain such linear orderings of cardinality kappa+ with the additional property that their square is the union of kappa-many chains. We give two constructions: directly building such examples using forcing, and also deriving their existence from combinatorial principles. The latter approach shows that such minimal non-sigma-scattered linear orders of cardinality kappa+ exist for every infinite cardinal kappa in Gödel's constructible universe, and also (using work of Rinot [28]) that examples must exist at successors of singular strong limit cardinals in the absence of inner models satisfying the existence of a measurable cardinal mu of Mitchell order mu++.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.physletb.2022.136985
