THEORETICAL CALCULATIONS OF SINGLET–SINGLET AND SINGLET–TRIPLET RADIATIVE LIFETIMES IN AROMATIC HYDROCARBONS

1971 ◽  
pp. 187-200
Author(s):  
Richard M. Hedges ◽  
Owen C. Hofer
Keyword(s):  
Aromatic Hydrocarbons ◽  
Theoretical Calculations ◽  
Radiative Lifetimes

scholarly journals Gas-phase synthesis of benzene via the propargyl radical self-reaction

2021 ◽  
Vol 7 (21) ◽  
pp. eabf0360
Author(s):  
Long Zhao ◽  
Wenchao Lu ◽  
Musahid Ahmed ◽  
Marsel V. Zagidullin ◽  
Valeriy N. Azyazov ◽  
...  
Keyword(s):  
Gas Phase ◽  
Aromatic Hydrocarbons ◽  
Theoretical Calculations ◽  
Branching Ratios ◽  
Structural Isomers ◽  
Phase Synthesis ◽  
Solar Systems ◽  
Propargyl Radical ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Chemistry

Polycyclic aromatic hydrocarbons (PAHs) have been invoked in fundamental molecular mass growth processes in our galaxy. We provide compelling evidence of the formation of the very first ringed aromatic and building block of PAHs—benzene—via the self-recombination of two resonantly stabilized propargyl (C3H3) radicals in dilute environments using isomer-selective synchrotron-based mass spectrometry coupled to theoretical calculations. Along with benzene, three other structural isomers (1,5-hexadiyne, fulvene, and 2-ethynyl-1,3-butadiene) and o-benzyne are detected, and their branching ratios are quantified experimentally and verified with the aid of computational fluid dynamics and kinetic simulations. These results uncover molecular growth pathways not only in interstellar, circumstellar, and solar systems environments but also in combustion systems, which help us gain a better understanding of the hydrocarbon chemistry of our universe.

Laser-induced fluorescence experimental spectroscopy and theoretical calculations of uranium monoxide

2021 ◽  
Author(s):  
Xi-Lin Bai ◽  
Xue-Dong Zhang ◽  
Fu-Qiang Zhang ◽  
Timothy C. Steimle
Keyword(s):  
Chemical Bonding ◽  
Fluorescence Spectra ◽  
Theoretical Calculations ◽  
Branching Ratios ◽  
Laser Induced Fluorescence ◽  
Theory Model ◽  
Ligand Field ◽  
Excitation Spectra ◽  
Transition Dipole ◽  
Radiative Lifetimes

Abstract As a model molecule of actinide chemistry, UO molecule plays an important role in understanding the electronic structure and chemical bonding of actinide-containing species. We report a study of the laser-induced fluorescence spectra of the U16O and U18O using two-dimensional spectroscopy. Several rotationally resolved excitation spectra were investigated. Accurate molecular rotational constants and equilibrium internuclear distances were reported. Low-lying electronic states information was extracted from high resolution dispersed fluorescence spectra and analyzed by the ligand field theory model. The configuration of the ground state was determined as U2+(5f37s)O2-. The branching ratios, and the vibrational harmonic and anharmonic parameters were also obtained. Radiative lifetimes were determined by recording the time-resolved fluorescence spectroscopy. Transition dipole moments were calculated using the branching ratios and the radiative lifetimes. These findings were elucidated by using quantum-chemical calculations, and the chemical bonding was also analyzed. The findings presented in this work will enrich our understanding of actinide-containing molecules.

scholarly journals Fast screening of polycyclic aromatic hydrocarbons using trapped ion mobility spectrometry – mass spectrometry

2014 ◽  
Vol 6 (23) ◽  
pp. 9328-9332 ◽  
Author(s):  
A. Castellanos ◽  
P. Benigni ◽  
D. R. Hernandez ◽  
J. D. DeBord ◽  
M. E. Ridgeway ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Polycyclic Aromatic Hydrocarbons ◽  
Ion Mobility Spectrometry ◽  
Aromatic Hydrocarbons ◽  
Ion Mobility ◽  
Theoretical Calculations ◽  
Trapped Ion ◽  
Fast Screening ◽  
Trapped Ion Mobility Spectrometry ◽  
Polycyclic Aromatic

In the present paper, we showed the advantages of trapped ion mobility spectrometry coupled to mass spectrometry (TIMS-MS) combined with theoretical calculations for fast identification (millisecond timescale) of polycyclic aromatic hydrocarbons (PAH) compounds from complex mixtures.

scholarly journals One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

2020 ◽  
Vol 16 ◽  
pp. 791-797
Author(s):  
Ji Ma ◽  
Yubin Fu ◽  
Junzhi Liu ◽  
Xinliang Feng
Keyword(s):  
Energy Level ◽  
Aromatic Hydrocarbons ◽  
Energy Gap ◽  
Theoretical Calculations ◽  
Lumo Energy ◽  
One Pot ◽  
X Ray ◽  
X Ray Crystallography ◽  
Phenyl Rings ◽  
Palladium Catalyzed

A novel dicyclopenta-fused peropyrene derivative 1 was synthesized via a palladium-catalyzed four-fold alkyne annulation of 1,3,6,8-tetrabromo-2,7-diphenylpyrene (5) with diphenylacetylene. The annulative π-extension reaction toward 1 involved a twofold [3 + 2] cyclopentannulation and subsequent twofold [4 + 2] benzannulation. The structure of 1 is unambiguously confirmed by X-ray crystallography; 1 adopted a twisted geometry due to the steric hindrance of the phenyl rings and the hydrogen substituents at the bay regions. Notably, compound 1 exhibits a narrow energy gap (1.78 eV) and a lower LUMO energy level than the parent peropyrene without the fusion of the five-membered rings. In addition, the effects of the peri-fused pentagons on the aromaticity and molecular orbitals of 1 were evaluated by theoretical calculations. This work presents an efficient method to develop π-extended aromatic hydrocarbons with cyclopenta moieties.

scholarly journals Diels–Alder Cycloaddition to the Bay Region of Perylene and Its Derivatives as an Attractive Strategy for PAH Core Expansion: Theoretical and Practical Aspects

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5373
Author(s):  
Aneta Kurpanik ◽  
Marek Matussek ◽  
Piotr Lodowski ◽  
Grażyna Szafraniec-Gorol ◽  
Michał Krompiec ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Organic Synthesis ◽  
Aromatic Hydrocarbons ◽  
Theoretical Calculations ◽  
Modern Technology ◽  
Diels Alder ◽  
Point Of View ◽  
Synthetic Method ◽  
Polycyclic Aromatics ◽  
Polycyclic Aromatic

PAHs (polycyclic aromatics hydrocarbons), the compound group that contains perylene and its derivatives, including functionalized ones, have attracted a great deal of interest in many fields of science and modern technology. This review presents all of the research devoted to modifications of PAHs that are realized via the Diels–Alder (DA) cycloaddition of various dienophiles to the bay regions of PAHs, leading to the π-extension of the starting molecule. This type of annulative π-extension (APEX) strategy has emerged as a powerful and efficient synthetic method for the construction of polycyclic aromatic hydrocarbons and their functionalized derivatives, nanographenes, and π-extended fused heteroarenes. Then, [4 + 2] cycloadditions of ethylenic dienophiles, -N=N-, i.e., diazo-dienophiles and acetylenic dienophiles, are presented. This subject is discussed from the organic synthesis point of view but supported by theoretical calculations. The possible applications of DA cycloaddition to PAH bay regions in various science and technology areas, and the prospects for the development of this synthetic method, are also discussed.

XUV Absorption Spectra of Carbon Ions

1988 ◽  
Vol 102 ◽  
pp. 71-73
Author(s):  
E. Jannitti ◽  
P. Nicolosi ◽  
G. Tondello
Keyword(s):  
Absorption Spectra ◽  
Cross Section ◽  
Theoretical Calculations ◽  
Photoionization Cross Section ◽  
Carbon Ions

AbstractThe photoabsorption spectra of the carbon ions have been obtained by using two laser-produced plasmas. The photoionization cross-section of the CV has been absolutely measured and the value at threshold, σ=(4.7±0.5) × 10−19cm2, as well as its behaviour at higher energies agrees quite well with the theoretical calculations.

Relative Intensities in ED Patterns From Thin Gold Films

1972 ◽  
Vol 30 ◽  
pp. 636-637
Author(s):  
R. H. Morriss ◽  
J. D. C. Peng ◽  
C. D. Melvin
Keyword(s):  
Theoretical Calculations ◽  
Diffraction Theory ◽  
Gold Films ◽  
Reasonable Accuracy ◽  
Experimental Conditions ◽  
Crystal Perfection ◽  
Heavy Atoms ◽  
Fine Focus ◽  
Convergent Beam ◽  
Beam Diffraction

Although dynamical diffraction theory was modified for electrons by Bethe in 1928, relatively few calculations have been carried out because of computational difficulties. Even fewer attempts have been made to correlate experimental data with theoretical calculations. The experimental conditions are indeed stringent - not only is a knowledge of crystal perfection, morphology, and orientation necessary, but other factors such as specimen contamination are important and must be carefully controlled. The experimental method of fine-focus convergent-beam electron diffraction has been successfully applied by Goodman and Lehmpfuhl to single crystals of MgO containing light atoms and more recently by Lynch to single crystalline (111) gold films which contain heavy atoms. In both experiments intensity distributions were calculated using the multislice method of n-beam diffraction theory. In order to obtain reasonable accuracy Lynch found it necessary to include 139 beams in the calculations for gold with all but 43 corresponding to beams out of the [111] zone.

Effects of Higher-Order Laue Zone reflections on structure images

1993 ◽  
Vol 51 ◽  
pp. 450-451
Author(s):  
H. S. Kim ◽  
S. S. Sheinin
Keyword(s):  
Wave Vector ◽  
Theoretical Calculations ◽  
Reciprocal Lattice ◽  
Image Plane ◽  
Bloch Wave ◽  
Dynamical Theory ◽  
Higher Order ◽  
Lattice Image ◽  
Lattice Vector ◽  
Image Position

The importance of image simulation in interpreting experimental lattice images is well established. Normally, in carrying out the required theoretical calculations, only zero order Laue zone reflections are taken into account. In this paper we assess the conditions for which this procedure is valid and indicate circumstances in which higher order Laue zone reflections may be important. Our work is based on an analysis of the requirements for obtaining structure images i.e. images directly related to the projected potential. In the considerations to follow, the Bloch wave formulation of the dynamical theory has been used.The intensity in a lattice image can be obtained from the total wave function at the image plane is given by: where ϕg(z) is the diffracted beam amplitide given by In these equations,the z direction is perpendicular to the entrance surface, g is a reciprocal lattice vector, the Cg(i) are Fourier coefficients in the expression for a Bloch wave, b(i), X(i) is the Bloch wave excitation coefficient, ϒ(i)=k(i)-K, k(i) is a Bloch wave vector, K is the electron wave vector after correction for the mean inner potential of the crystal, T(q) and D(q) are the transfer function and damping function respectively, q is a scattering vector and the summation is over i=l,N where N is the number of beams taken into account.

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