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Sequential Femtosecond Optical Dynamics in Poly(phenylenevinylene), PPV
Author(s) -
Brunner K.,
Tortschanoff A.,
Warmuth Ch.,
Mollay B.,
Kauffmann H. F.
Publication year - 1998
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199801)205:1<325::aid-pssb325>3.0.co;2-3
Subject(s) - femtosecond , luminescence , excitation , molecular physics , phenylene , relaxation (psychology) , population , materials science , pauli exclusion principle , atomic physics , chemistry , optoelectronics , optics , laser , physics , polymer , condensed matter physics , psychology , social psychology , demography , quantum mechanics , sociology , composite material
In the weak coupling, molecular site approach poly(phenylene‐vinylene) (PPV) is modeled in terms of conformational breaks that statistically interrupt the π‐conjugation length and give rise (i) to segmental subunits, distributed in self‐energy and (ii) to a density‐of‐states (DOS) of S 1 levels upon electronic excitation. For two different, spectral positions of the luminescence probe window, it is demonstrated that intra‐DOS cascading, i.e. the femtosecond population transfer from high‐energy tail‐states to low‐energy wing states can be probed in real time by means of luminescence up‐conversion measurements. Parametrized, biexponential profiles, i.e. a fs decay (τ 1 ≈ 350 fs) and a complementary pattern containing a significant fs rise (τ 1 ≈ 310 fs) have been found for the luminescence evolutions at 2.7 and 2.25 eV, respectively, that directly trace the sequential dynamics of optical spectral diffusion. A many‐body treatment based upon a combined MC and a Pauli‐master equation analysis has yielded quite satisfactory results in favor of the distributed nature of the optical relaxation process.