Pump-probe spectroscopy and the exciton delocalization length in molecularaggregates

Citation
Ld. Bakalis et J. Knoester, Pump-probe spectroscopy and the exciton delocalization length in molecularaggregates, J PHYS CH B, 103(31), 1999, pp. 6620-6628
Citations number
44
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF PHYSICAL CHEMISTRY B
ISSN journal
15206106 → ACNP
Volume
103
Issue
31
Year of publication
1999
Pages
6620 - 6628
Database
ISI
SICI code
1520-6106(19990805)103:31<6620:PSATED>2.0.ZU;2-S
Abstract
Using numerical simulations, we investigate to what extent the pump-probe s pectrum can be used as a tool to determine the exciton delocalization lengt h in disordered molecular (J) aggregates. We compare the delocalization len gth obtained through heuristic arguments from the spectral separation betwe en the bleaching and the one- to two-exciton induced absorption features in this spectrum to the delocalization length obtained from the participation ratio at the J band center. We find that up to a certain saturation length these two delocalization lengths are indeed proportional. In the case of l ong-pulse two-color pump-probe spectra, the slope of this linear scaling is insensitive to the pump frequency; it is sensitive to the width of the pro be pulse. Beyond the saturation length, which is determined by the homogene ous line width of the exciton transitions, both the two-color and the short -pulse pump-probe spectra saturate and no longer can be used as a measure f or the delocalization length. The latter applies to the B850 ring of bacter ial antenna complexes.