نتایج جستجو برای: photochemical

تعداد نتایج: 10629  

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2014
Stefan Ruetzel Meike Diekmann Patrick Nuernberger Christof Walter Bernd Engels Tobias Brixner

Coherent multidimensional electronic spectroscopy is commonly used to investigate photophysical phenomena such as light harvesting in photosynthesis in which the system returns back to its ground state after energy transfer. By contrast, we introduce multidimensional spectroscopy to study ultrafast photochemical processes in which the investigated molecule changes permanently. Exemplarily, the ...

Journal: :Bulletin of environmental contamination and toxicology 2001
C Rioboo D Franqueira M L Canle C Herrero A Cid

Photodegradation is one of the processes that pesticides may undergo once dispersed in the environment. It requires an adequate overlapping between the emission spectrum of the light source and the absorption spectrum of the compound to be degraded. When such condition is fulfilled, molecules undergo light absorption, being promoted to an excited electronic state, from where they can relax via ...

Journal: :Environmental Health Perspectives 1979
T Yanagimoto E Yamamoto

The hockey stick regression method is a convenient method to estimate safe doses, which is a kind of regression method using segmented lines. The method seems intuitively to be useful, but needs the assumption of the existence of the positive threshold value. The validity of the assumption is considered to be difficult to be shown. The alternative methods which are not based on the assumption, ...

2005
P. Sharma R. K. Vatsa S. K. Kulshreshtha

The field of gas phase photochemistry has progressed explosively in the past few decades due to the development of ultra fast high power lasers. Unique properties of lasers such as monochromaticity, coherence, tunability over a wide wavelength range and high intensity makes them a powerful pump and probe tool for a number of spectroscopic as well as photochemical studies like laser induced fluo...

Journal: :Journal of the American Chemical Society 2018

2007
Stefano Protti Daniele Dondi Maurizio Fagnoni Angelo Albini

A series of photochemical reactions are assessed under the environmental aspect by using Eissen and Metzger’s EATOS (environmental assessment tool for organic syntheses) method and are compared with strictly analogous thermal processes. These include C–C bond-forming reactions (arylation and alkylation) and selective oxidation and reduction reactions. In most cases, the photochemical method is ...

2005
Adalgisa Sinicropi Tadeusz Andruniow Luca De Vico Nicolas Ferré Massimo Olivucci

In this paper, we discuss the results of our recent studies on the molecular mechanism, which stand at the basis of the photochemical processes occurring in photobiological systems. These results are obtained using modern, robust, and fairly accurate high-level quantum chemical methods.

Journal: :Chemosphere 2009
Bernd R T Simoneit Yunping Xu Renato R Neto Joshua B Cloutier Rudolf Jaffé

The reactivity of higher plant derived 3-oxy-triterpenoids to sunlight was investigated using a series of pure reference standards both under simulated and real solar exposure. The majority of the exposed compounds showed reactivity to light, particularly to simulated sunlight and among others generated seco-derivatives. While photochemical processes have been suggested for the formation of suc...

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