Electronic absorption spectrum and π-electronic structure of cryptocyanine

1980 ◽  
Vol 45 (2) ◽  
pp. 307-320 ◽  
Author(s):  
Miloš Titz ◽  
Antonín Novák ◽  
Viktor Řehák
Keyword(s):  
Absorption Spectrum ◽  
Electronic Structure ◽  
Dipole Moment ◽  
Excited State ◽  
Absorption Band ◽  
Electronic Absorption ◽  
Quantum Chemical ◽  
Fluorescence Excitation ◽  
Real Geometry ◽  
Optimum Model

Absorption, fluorescence excitation and APF spectra of cryptocyanine have been measured. Dipole moment of the respective S1 excited state has been estimated from shifts of the marked maximum of the first absorption band in various solvents. On the basis of quantum-chemical calculations carried out by the PPP method in the approximation of quasi-real geometry we have received the optimum model of π-electronic structure of the cryptocyanine molecule and therefrom the theoretical electronic singlet spectrum inclusive character of the S0 - S1 transition.

scholarly journals Determining Partial Atomic Charges for Liquid Water: Assessing Electronic Structure and Charge Models

2020 ◽  
Author(s):  
Bowen Han ◽  
Christine Isborn ◽  
Liang Shi
Keyword(s):  
Electronic Structure ◽  
Dipole Moment ◽  
Charge Transfer ◽  
Liquid Water ◽  
Quantum Chemical ◽  
Water Dimer ◽  
Atomic Charges ◽  
Molecular Dipole ◽  
Molecular Dipole Moment ◽  
Partial Atomic Charges

Partial atomic charges provide an intuitive and efficient way to describe the charge distribution and the resulting intermolecular electrostatic interactions in liquid water. Many charge models exist and it is unclear which model provides the best assignment of partial atomic charges in response to the local molecular environment. In this work, we systematically scrutinize various electronic structure methods and charge models (Mulliken, Natural Population Analysis, CHelpG, RESP, Hirshfeld, Iterative Hirshfeld, and Bader) by evaluating their performance in predicting the dipole moments of isolated water, water clusters, and liquid water as well as charge transfer in the water dimer and liquid water. Although none of the seven charge models is capable of fully capturing the dipole moment increase from isolated water (1.85 D) to liquid water (about 2.9 D), the Iterative Hirshfeld method performs best for liquid water, reproducing its experimental average molecular dipole moment, yielding a reasonable amount of intermolecular charge transfer, and showing modest sensitivity to the local water environment. The performance of the charge model is dependent on the choice of the density functional and the quantum treatment of the environment. The computed molecular dipole moment of water generally increases with the percentage of the exact Hartree-Fock exchange in the functional, whereas the amount of charge transfer between molecules decreases. For liquid water, including two full solvation shells of surrounding water molecules (within about 5.5 A of the central water) in the quantum-chemical calculation converges the charges of the central water molecule. Our final pragmatic quantum-chemical charge assigning protocol for liquid water is the Iterative Hirshfeld method with M06-HF/aug-cc-pVDZ and a quantum region cutoff radius of 5.5 A.<br>

ChemInform Abstract: Excited-State Electronic Structure of Conjugated Oligomers and Polymers: A Quantum-Chemical Approach to Optical Phenomena

ChemInform ◽  
2010 ◽  
Vol 30 (21) ◽  
pp. no-no
Author(s):  
Jean-Luc Bredas ◽  
Jerome Cornil ◽  
David Beljonne ◽  
Donizetti A. Dos Santos ◽  
Zhigang Shuai
Keyword(s):  
Electronic Structure ◽  
Excited State ◽  
Quantum Chemical ◽  
Conjugated Oligomers ◽  
Chemical Approach ◽  
Quantum Chemical Approach ◽  
Optical Phenomena

The electronic absorption spectrum of NHD

1979 ◽  
Vol 57 (5) ◽  
pp. 761-766 ◽  
Author(s):  
D. A. Ramsay ◽  
F.D. Wayne
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Electronic Absorption Spectrum ◽  
Electronic Absorption ◽  
Rotational Constants ◽  
Axis Switching

Rotational assignments are given for about 350 lines in the (0,9,0)–(0,0,0), (0,10,0)–(0,0,0), and (0,11,0)–(0,0,0) bands in the electronic absorption spectrum of NHD. The Σ and Δ sub-bands have been identified for the bands with ν2′ odd and the Π sub-band for the band with ν2′ even.Ground state rotational and spin–rotational constants have been determined. The principal constants in reciprocal centimetres are: A = 20.1162(32), B = 8.1114(16), C = 5.6681(16), εaa = −0.2324(51),εbb = −0.0373ε, εcc = −0.0019ε, where the error limits are 1σ. Term values are tabulated for both the ground and excited state levels.Several 'axis-switching' branches have been identified in agreement with the predictions of Hougen and Watson.

scholarly journals Determining Partial Atomic Charges for Liquid Water: Assessing Electronic Structure and Charge Models

2020 ◽  
Author(s):  
Bowen Han ◽  
Christine Isborn ◽  
Liang Shi
Keyword(s):  
Electronic Structure ◽  
Dipole Moment ◽  
Charge Transfer ◽  
Liquid Water ◽  
Quantum Chemical ◽  
Water Dimer ◽  
Atomic Charges ◽  
Molecular Dipole ◽  
Molecular Dipole Moment ◽  
Partial Atomic Charges

Partial atomic charges provide an intuitive and efficient way to describe the charge distribution and the resulting intermolecular electrostatic interactions in liquid water. Many charge models exist and it is unclear which model provides the best assignment of partial atomic charges in response to the local molecular environment. In this work, we systematically scrutinize various electronic structure methods and charge models (Mulliken, Natural Population Analysis, CHelpG, RESP, Hirshfeld, Iterative Hirshfeld, and Bader) by evaluating their performance in predicting the dipole moments of isolated water, water clusters, and liquid water as well as charge transfer in the water dimer and liquid water. Although none of the seven charge models is capable of fully capturing the dipole moment increase from isolated water (1.85 D) to liquid water (about 2.9 D), the Iterative Hirshfeld method performs best for liquid water, reproducing its experimental average molecular dipole moment, yielding a reasonable amount of intermolecular charge transfer, and showing modest sensitivity to the local water environment. The performance of the charge model is dependent on the choice of the density functional and the quantum treatment of the environment. The computed molecular dipole moment of water generally increases with the percentage of the exact Hartree-Fock exchange in the functional, whereas the amount of charge transfer between molecules decreases. For liquid water, including two full solvation shells of surrounding water molecules (within about 5.5 A of the central water) in the quantum-chemical calculation converges the charges of the central water molecule. Our final pragmatic quantum-chemical charge assigning protocol for liquid water is the Iterative Hirshfeld method with M06-HF/aug-cc-pVDZ and a quantum region cutoff radius of 5.5 A.<br>

Density-based descriptors and exciton analyses for visualizing and understanding the electronic structure of excited states

2019 ◽  
Vol 21 (6) ◽  
pp. 2843-2856 ◽  
Author(s):  
Stefanie A. Mewes ◽  
Andreas Dreuw
Keyword(s):  
Electronic Structure ◽  
Excited State ◽  
Excited States ◽  
Quantum Chemical

Quantum-chemical exciton analysis allows for quantitative, yet facile characterization of excited-state electronic structure and advanced multi-parameter benchmarking.

Sign in / Sign up

Export Citation Format

Share Document