scholarly journals Electron delocalization and aromaticity in low-lying excited states of archetypal organic compounds

2011 ◽  
Vol 13 (46) ◽  
pp. 20690 ◽  
Author(s):  
Ferran Feixas ◽  
Jelle Vandenbussche ◽  
Patrick Bultinck ◽  
Eduard Matito ◽  
Miquel Solà
Keyword(s):  
Organic Compounds ◽  
Excited States ◽  
Electron Delocalization

scholarly journals Shannon, Rényi, Tsallis Entropies and Onicescu Information Energy for Low-Lying Singly Excited States of Helium

Atoms ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 70 ◽  
Author(s):  
Jen-Hao Ou ◽  
Yew Kam Ho
Keyword(s):  
Excited States ◽  
Shannon Entropy ◽  
Electronic Structures ◽  
Tsallis Entropy ◽  
Renyi Entropy ◽  
Rényi Entropy ◽  
Electron Delocalization ◽  
Information Theoretic ◽  
Molecular Systems ◽  
Information Energy

Knowledge of the electronic structures of atomic and molecular systems deepens our understanding of the desired system. In particular, several information-theoretic quantities, such as Shannon entropy, have been applied to quantify the extent of electron delocalization for the ground state of various systems. To explore excited states, we calculated Shannon entropy and two of its one-parameter generalizations, Rényi entropy of order α and Tsallis entropy of order α , and Onicescu Information Energy of order α for four low-lying singly excited states (1s2s 1 S e , 1s2s 3 S e , 1s3s 1 S e , and 1s3s 3 S e states) of helium. This paper compares the behavior of these three quantities of order 0.5 to 9 for the ground and four excited states. We found that, generally, a higher excited state had a larger Rényi entropy, larger Tsallis entropy, and smaller Onicescu information energy. However, this trend was not definite and the singlet–triplet reversal occurred for Rényi entropy, Tsallis entropy and Onicescu information energy at a certain range of order α .

scholarly journals Photooxidants from Brown Carbon and Other Chromophores in Illuminated Particle Extracts

2018 ◽  
Author(s):  
Richie Kaur ◽  
Jacqueline R. Labins ◽  
Scarlett S. Helbock ◽  
Wenqing Jiang ◽  
Keith Bein ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Organic Compounds ◽  
Excited States ◽  
Liquid Water ◽  
Light Absorption ◽  
Singlet Molecular Oxygen ◽  
Brown Carbon ◽  
Aggregate Rate ◽  
Triplet Excited States

Abstract. While photooxidants are important in atmospheric condensed phases, there are very few measurements in particulate matter (PM). Here we measure light absorption and the concentrations of three photooxidants – hydroxyl radical (•OH), singlet molecular oxygen (1O2*) and oxidizing triplet excited states of organic matter (3C*) – in illuminated aqueous extracts of wintertime particles from Davis, California. 1O2* and 3C*, which are formed from photoexcitation of brown carbon (BrC), have not been previously measured in PM. In the extracts, mass absorption coefficients for dissolved organic compounds (MACDOC) at 300 nm range between 13,000–30,000 cm2 g–C–1 and are approximately twice as high as previous values in Davis fogs. The average (± 1σ) •OH steady-state concentration in particle extracts is 4.7 (± 1.9) × 10−16 M, which is very similar to previous values in fog, cloud and rain: although our particle extracts are more concentrated, the resulting enhancement in the rate of •OH photoproduction is essentially cancelled out by a corresponding enhancement in concentrations of natural sinks for •OH. In contrast, concentrations of the two oxidants formed primarily from brown carbon (i.e., 1O2* and 3C*) are both enhanced in the particle extracts compared to Davis fogs, a result of higher concentrations of dissolved organic carbon and faster rates of light absorption in the extracts. The average 1O2* concentration in the PM extracts is 1.6 (± 0.5) × 10−12 M, seven times higher than past fog measurements, while the average concentration of oxidizing triplets is 1.0 (± 0.4) × 10−13 M, nearly double the average Davis fog value. Additionally, the rates of 1O2* and 3C* photoproduction are both well correlated with the rate of sunlight absorption. While concentrations of 1O2* and 3C* are higher in our PM extracts compared to fog, the extracts are approximately 1000 times more dilute than water-containing ambient PM. Since we cannot experimentally measure photooxidants under these ambient conditions, we measured the effect of PM dilution on oxidant concentrations and then extrapolated to ambient particle conditions. As the particle mass concentration in the extracts increases, measured concentrations of •OH remain relatively unchanged, 1O2* increases linearly, and 3C* concentrations increase less than linearly, likely due to quenching by dissolved organics. Based on our measurements, and accounting for additional sources and sinks that should be important under PM conditions, we estimate that [•OH] in particles is essentially the same as in fog waters, [3C*] is higher in PM by nearly a factor of 3, and [1O2*] is enhanced by a factor of roughly 600. Because of these enhancements in 1O2* and 3C* concentrations, the lifetimes of some highly soluble organics appear to be much shorter in particle liquid water than under foggy/cloudy conditions. Based on our extrapolated rates of formation, BrC-derived singlet molecular oxygen and triplet excited states are the dominant sinks for organic compounds in particle liquid water, with an aggregate rate of reaction for each oxidant that is approximately 200–300 times higher than the aggregate rate of reactions for organics with •OH. For individual, highly soluble reactive organic compounds it appears that 1O2* is the major sink in particle water. Triplet excited states are likely also important in the fate of individual particulate organics, but assessing this requires additional measurements of triplet interactions with dissolved organic carbon in natural samples.

Does density functional theory contribute to the understanding of excited states of unsaturated organic compounds?

1999 ◽  
Vol 97 (7) ◽  
pp. 859-868 ◽  
Author(s):  
David J. Tozer ◽  
Roger D. Amos ◽  
Nicholas C. Handy ◽  
Bjorn O. Roos ◽  
Luis Serrano-ANDRES
Keyword(s):  
Density Functional Theory ◽  
Organic Compounds ◽  
Excited States ◽  
Density Functional ◽  
Functional Theory

ChemInform Abstract: Multiconfigurational Perturbation Theory Applied to Excited States of Organic Compounds

ChemInform ◽  
2010 ◽  
Vol 31 (1) ◽  
pp. no-no
Author(s):  
M. Merchan ◽  
L. Serrano-Andres ◽  
M. P. Fulscher ◽  
B. O. Roos
Keyword(s):  
Perturbation Theory ◽  
Organic Compounds ◽  
Excited States

Electron delocalization and electron density of small polycyclic aromatic hydrocarbons in singlet excited states

2016 ◽  
Vol 18 (17) ◽  
pp. 11792-11799 ◽  
Author(s):  
Mar Estévez-Fregoso ◽  
Jesús Hernández-Trujillo
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Electron Density ◽  
Excited States ◽  
Aromatic Hydrocarbons ◽  
Electron Delocalization ◽  
Excitation Energies ◽  
Polycyclic Aromatic

Electron delocalization allows us to study the similarity and aromaticity of PAHs in excited states, and can be correlated with the excitation energies.

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