Twin states and conical intersections in linear polyenes

W. Fuß, Y. Haas, S. Zilberg

פרסום מחקרי: פרסום בכתב עתמאמרביקורת עמיתים

113 ציטוטים ‏(Scopus)

תקציר

We suggest for linear conjugated polyenes a twin state model which represents the ground state (S0) and first excited state (S1) as a superposition of mainly two mesomeric structures, the fully spin-paired one and a diradical. This model rationalizes why the bond-length alternation, which is pronounced in S0, more or less disappears in S1 and why the bond-alternation vibration (highest frequency C=C stretch) is raised in S1 and depressed in S0. The similarity to the Peierls effect and Kohn anomaly in one-dimensional metals is emphasized. Moreover, the conical intersection between S2 and S1 is qualitatively predicted, and invoking in addition, some spectroscopic and other observations and the phase-change rule, that between S1 and S0 can also be predicted. Compared with the consideration of densities of states and matrix elements, these intersections more satisfactorily explain the S2/S1 and S1/S0 internal conversions and their dependence on chain length, substituents, solvent and temperature and is furthermore consistent with photochemistry. This also includes an exponential gap rule for the internal-conversion rates, which is derived from a proposed dependence of the energy at the intersection on the S1-S0 energy gap. (C) 2000 Elsevier Science B.V.

שפה מקוריתאנגלית
עמודים (מ-עד)273-295
מספר עמודים23
כתב עתChemical Physics
כרך259
מספר גיליון2-3
מזהי עצם דיגיטלי (DOIs)
סטטוס פרסוםפורסם - 15 ספט׳ 2000
פורסם באופן חיצוניכן

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