| Jazyk: |
angličtina |
| Rok vydání: |
1995 |
| Předmět: |
|
| Zdroj: |
Physical Review B. 52(24):17158-17164 |
| ISSN: |
1098-0121 |
| DOI: |
10.1103/physrevb.52.17158 |
| Popis: |
The electric-dipole-forbidden T-1(1g) excitonic state of solid C-60 at hw=1.81 eV can be probed with a second-harmonic generation (SHG) experiment. We show that the SHG line shape depends strongly on the degree of rotational order. We observe a splitting into two peaks below the rotational ordering phase-transition temperature of 260 K. The origin of this splitting is discussed in terms of a possible Jahn-Teller effect, a possible Davydov splitting due to the four molecules per unit cell in the low-temperature phase, and a mixing of the nearly degenerate T-1(1g) and (1)G(g) free molecule states because of the lower symmetry in the solid. The exciton band structure is calculated with a charge-transfer-mediated propagation mechanism as suggested by Lof et al.(2) and with one-electron (-hole) transfer integrals determined from band-structure calculations. Comparison with our experimental SHG data leads to a reasonable agreement and shows that a mixing of (1)T(1)g and (1)G(g) states may explain the splitting at low temperature. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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