1,721,002 research outputs found
Exploring molecular dynamics for coherent control
Get PDFDie durch Femtosekunden-Laserimpulse induzierte Dissoziationsdynamik von CsCl und von CH2BrCl werden untersucht und die Möglichkeiten der kohärenten Kontrolle der Dissoziation werden diskutiert. Im Fall des CsCl Moleküls, werden die Pumpe-Probe Messergebnissen von Dr. Andreas Glaß (Glaß et al. Appl. Phys. B 71, 267, 2000) mit Hilfe von quantendynamischen Simulationen aufgeklärt. Die Simulation des Ionizationsprozesses wird durch neuartige Anwendung einer nichtreflektierenden Randbedingung beschleunigt. Diese Methode wird numerisch getestet. Durch ab initio Berechnungen entsprechend dem MS-CASPT2 Verfahren werden vertikale Anregungsenergien und Oszillatorenstärken für die niedrigsten Singulett-Elektronenzustände des CH2BrCl Moleküls und seiner CH2Br und CH2Cl Radikale bestimmt. Außerdem werden eindimensionale Born-Oppenheimer Potentialkurven und Übergangsdipolmomentkurven für beide Kohlenstoff-Halogen Reaktionskoordinaten berechnet. Diese werden in nachfolgenden quantendynamischen Simulationen benutzt, wobei auch nichtadiabatische Effekte berücksichtigt werden. Auf Grund der Ergebnisse wird ein Zweiimpuls-Kontrollschema für die selektive Aufspaltung der stärkeren Kohlenstoff-Halogen Bindung des CH2BrCl Moleküls vorgeschlagen. Im Anhang werden theoretische Untersuchungen für zeitaufgelöste Röntgenbeugung im Molekülkristall dargestellt
Acceptor Energy Offset Manages Ultrafast Recombination Dynamics in Donor-Acceptor Mixtures
Get PDFWe study charge recombination rates in blends of MEH-PPV and a comprehensive set of low molecular-weight fluorine-based acceptors, using visible-pump – IR-probe photoinduced absorption technique. The positions of acceptor’s HOMO-LUMO levels are engineered by addition of different chemical substituents. The results clearly show the exponential scaling of the charge recombination rate with the acceptor LUMO energy. The minimal donor-acceptor LUMO energy difference required to form a CTC state is estimated as ~0.25 eV.
Ultrafast Pump-Push Photocurrent Spectroscopy of Organic Photoconversion Systems
Get PDFNovel optical pump-push – photocurrent probe ultrafast spectroscopy experiments on organic photoconversion systems show that excessive excitation energy in such systems is not lost but used to reach delocalised states that act as the gateway for long-range charge separation. We also show that the developed experimental approach can be generalised to inorganic and hybrid photoconversion systems.
Ultrafast ignition of a uni-directional molecular motor
Get PDFLight-driven molecular motors convert light into mechanical energy via excited state reactions. In this work we follow sub-picosecond primary events in the cycle of a two-stroke unidirectional motor by fluorescence up-conversion and transient absorption.
Probing the origin of fluorescence quenching of a graphene-porphyrin hybrid material
Get PDFWe report transient absorption spectroscopic studies on the hybrid material composed of porphyrin molecules covalently attached to graphene for investigating the mechanism underlying the reported fluorescence quenching of porphyrin in the hybrid. Excited state dynamics of pure graphene suspension and porphyrin have also been studied as reference samples. A fast excited state decay was observed in the hybrid.
Exciton and Hole-Transfer Dynamics in Polymer:Fullerene Blends
Get PDFUltrafast hole transfer dynamics from fullerene derivative to polymer in bulk heterojunction blends are studied with visible-pump – IR-probe spectroscopy. The hole transfer process is found to occur in 50/300 fs next to the interface, while a longer 15-ps time is attributed to exciton diffusion towards interface in PC71BM domains. High polaron generation efficiency in P3HT blends indicates excellent intercalation between the polymer and the fullerene even at highest PC71BM concentration thereby yielding a valuable information on the blend morphology
Probing the origin of fluorescence quenching of a graphene-porphyrin hybrid material
Get PDFWe report transient absorption spectroscopic studies on the hybrid material composed of porphyrin molecules covalently attached to graphene for investigating the mechanism underlying the reported fluorescence quenching of porphyrin in the hybrid. Excited state dynamics of pure graphene suspension and porphyrin have also been studied as reference samples. A fast excited state decay was observed in the hybrid
Ultrafast Pump-Push Photocurrent Spectroscopy of Organic Photoconversion Systems
No full textNovel optical pump-push – photocurrent probe ultrafast spectroscopy experiments on organic photoconversion systems show that excessive excitation energy in such systems is not lost but used to reach delocalised states that act as the gateway for long-range charge separation. We also show that the developed experimental approach can be generalised to inorganic and hybrid photoconversion systems
Ultrafast Pump-Push Photocurrent Spectroscopy of Organic Photoconversion Systems
Get PDFNovel optical pump-push – photocurrent probe ultrafast spectroscopy experiments on organic photoconversion systems show that excessive excitation energy in such systems is not lost but used to reach delocalised states that act as the gateway for long-range charge separation. We also show that the developed experimental approach can be generalised to inorganic and hybrid photoconversion systems
Acceptor Energy Offset Manages Ultrafast Recombination Dynamics in Donor-Acceptor Mixtures
Get PDFWe study charge recombination rates in blends of MEH-PPV and a comprehensive set of low molecular-weight fluorine-based acceptors, using visible-pump – IR-probe photoinduced absorption technique. The positions of acceptor’s HOMO-LUMO levels are engineered by addition of different chemical substituents. The results clearly show the exponential scaling of the charge recombination rate with the acceptor LUMO energy. The minimal donor-acceptor LUMO energy difference required to form a CTC state is estimated as ~0.25 eV
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