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| Main Authors: | , |
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| Format: | Preprint |
| Published: |
2026
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| Online Access: | https://arxiv.org/abs/2603.08160 |
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| _version_ | 1866911498872291328 |
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| author | Ichert, Alexandru G. Barford, William |
| author_facet | Ichert, Alexandru G. Barford, William |
| contents | We define and calculate the triplet-pair population of the $2^1A_g$ dark state in polyenes, as predicted by the $π$-electron Pariser-Parr-Pople (PPP) model, for chains of 8 to 14 C-atoms and Coulomb interaction parameter between 4-14 eV. Our definition of the triplet-pair population is motivated by a two-particle model of the $2^1A_g$ state. We use DMRG to solve the PPP model and we exploit the MPS representation of the DMRG wavefunction to compute the triplet-pair population. Using our results for short chain sizes, we predict a finite-size scaling value of the triplet-pair population of ca. 75% for realistic Coulomb interactions for polyene chains. Our results agree with other theoretical work on the doubly-excited character of polyenes, and represents further evidence that the $2^1A_g$ state is predominantly triplet-pair in character - with implications for singlet fission mechanisms in polyenes. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_08160 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Triplet-Pair Character of the $2^1A_g$ Dark State of Polyenes Ichert, Alexandru G. Barford, William Chemical Physics We define and calculate the triplet-pair population of the $2^1A_g$ dark state in polyenes, as predicted by the $π$-electron Pariser-Parr-Pople (PPP) model, for chains of 8 to 14 C-atoms and Coulomb interaction parameter between 4-14 eV. Our definition of the triplet-pair population is motivated by a two-particle model of the $2^1A_g$ state. We use DMRG to solve the PPP model and we exploit the MPS representation of the DMRG wavefunction to compute the triplet-pair population. Using our results for short chain sizes, we predict a finite-size scaling value of the triplet-pair population of ca. 75% for realistic Coulomb interactions for polyene chains. Our results agree with other theoretical work on the doubly-excited character of polyenes, and represents further evidence that the $2^1A_g$ state is predominantly triplet-pair in character - with implications for singlet fission mechanisms in polyenes. |
| title | Triplet-Pair Character of the $2^1A_g$ Dark State of Polyenes |
| topic | Chemical Physics |
| url | https://arxiv.org/abs/2603.08160 |