Modeling of multi-exciton transient absorption spectra of protochlorophyllide aggregates in aqueous solution.
نویسندگان
چکیده
Protochlorophyllide (Pchlide) is a natural porphyrin, a precursor of chlorophyll, synthesized by plants for its photosynthetic apparatus. The pigment spontaneously forms aggregates when dissolved in neat water solution. We present here calculations of the transient absorption spectra and its comprising components (ground-state bleach, stimulated emission, and excited-state absorption) for a strongly excitonically coupled linear chain of four Pchlide chromophores, using exciton theory with phenomenological Gaussian line shapes and without energetic disorder. A refined multiexciton model that includes static disorder is applied to fit the experimental power-dependent transient absorption spectra of aqueous protochlorophyllide and the kinetics for delay times up to 20 ps after photoexcitation. We show that population up to the 4-exciton manifold is sufficient to explain the pronounced saturation of the bleaching and the shape changes in the instantaneous, t = 0.2 ps transient spectra when the pulse energy is increased from 10 to 430 nJ per pulse. The decay of the multiexciton manifold is relatively slow and is preceded by a spectroscopically distinct process. We suggest that the exciton states in the Pchlide aggregates are mixed with charge-transfer states (CTS) and that the population and repopulation of the CTS coupled to the exciton states explains the relatively slow decay of the multiexciton manifold. The relevance of our results to the optical properties and dynamics of natural photosynthetic complexes and the possible physical origin of CTS formation are discussed.
منابع مشابه
Nche Tumasang Fofang A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE
Optical Properties of Strongly Coupled Plasmon-Exciton Hybrid Nanostructures by Nche Tumasang Fofang Strongly coupled plasmon-exciton hybrid nanostructures are fabricated and their optical properties are studied. The plasmonic and excitonic systems are gold nanoshells and J-aggregates, respectively. Gold nanoshells are tunable plasmonic core-shell nanoparticles which can sustain distinct dipole...
متن کاملElectric field-controlled dissociation and association of porphyrin J-aggregates in aqueous solution.
The electrooptic effects of porphyrin J-aggregates of tetraphenyl porphyrin tetrasulfonic acid (TPPS) in aqueous solution were studied using electroabsorption (EA) spectroscopy. When the J-aggregates were three-dimensionally distributed, the EA spectra exhibited broadening in the exciton band. When a DC or AC electric field was applied for a long time, the J-aggregates with KCl were dissociated...
متن کاملIon exchange growth of Zinc Sulfide quantum dots in aqueous solution
We report the growth by ion exchange synthesis of ZnS nanoparticles in MCM-41 matrices using Zn (CH3COO)2 and Na2S starting sources. The final product (ZnS/MCM-41) was characterized by X-ray diffraction (XRD) pattern, transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectrometry (IR) and UV-vis spectroscopy. Its crystalline st...
متن کاملTowards an ab initio theory for metal L-edge soft X-ray spectroscopy of molecular aggregates
The Frenkel exciton model was adapted to describe X-ray absorption and resonant inelastic scattering spectra of polynuclear transition metal complexes by means of the restricted active space self-consistent field method. The proposed approach allows to substantially decrease the requirements on computational resources if compared to a full supermolecular quantum chemical treatment. This holds t...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- The journal of physical chemistry. A
دوره 115 43 شماره
صفحات -
تاریخ انتشار 2011