scholarly journals Anharmonic excited state frequencies of para-difluorobenzene, toluene and catechol using analytic RI-CC2 second derivatives

2019 ◽  
Vol 21 (26) ◽  
pp. 14063-14072 ◽  
Author(s):  
David P. Tew ◽  
Christof Hättig ◽  
Nora K. Graf
Keyword(s):  
Excited State ◽  
Electronic State ◽  
Excited Electronic State ◽  
Second Derivatives

Analytic second nuclear derivatives for excited electronic state energies have been implemented for RI-CC2, CIS(D) and ADC(2) models and used in VPT2 calculations of excited state frequencies.

Variational Method for Estimating the Dipole Moment in the Second Excited State of Fluorescein Molecule from its Electronic UV Absorption Spectra

2019 ◽  
Vol 70 (10) ◽  
pp. 3538-3544
Author(s):  
Alina Costina Luca ◽  
Ana Cezarina Morosanu ◽  
Irina Macovei ◽  
Dan Gheorghe Dimitriu ◽  
Dana Ortansa Dorohoi ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Variational Method ◽  
Electronic State ◽  
Excited Electronic State ◽  
Spectral Band ◽  
Uv Absorption ◽  
Optical Parameters ◽  
Electrical Permittivity ◽  
Fluorescein Molecule

Electro-optical parameters of fluorescein molecule in the second excited electronic state and information on the interactions with solvents were obtained from a solvatochromic study. Parameters of the solvents such as the refractive index, electrical permittivity and Kamlet-Taft parameters (hydrogen bond acidity and basicity) were related with the experimentally recorded shifts of UV absorption spectral band of fluorescein dissolved in several solvents. Through a variational method, the electric dipole moment and polarizability in excited state of fluorescein molecule were estimated. The calculus requires some parameters of the fluorescein molecule in the ground electronic state, which were determined through a quantum-mechanical study.

scholarly journals Variational Method for Estimating the Dipole Moment in the Second Excited State of Fluorescein Molecule from its Electronic UV Absorption Spectra

2019 ◽  
Vol 70 (10) ◽  
pp. 3538-3544
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Variational Method ◽  
Electronic State ◽  
Excited Electronic State ◽  
Spectral Band ◽  
Uv Absorption ◽  
Quantum Mechanical ◽  
Optical Parameters ◽  
Fluorescein Molecule

Electro-optical parameters of fluorescein molecule in the second excited electronic state and information on the interactions with solvents were obtained from a solvatochromic study. Parameters of the solvents such as the refractive index, electrical permittivity and Kamlet-Taft parameters (hydrogen bond acidity and basicity) were related with the experimentally recorded shifts of UV absorption spectral band of fluorescein dissolved in several solvents. Through a variational method, the electric dipole moment and polarizability in excited state of fluorescein molecule were estimated. The calculus requires some parameters of the fluorescein molecule in the ground electronic state, which were determined through a quantum-mechanical study. Keywords: fluorescein; solvatochromism; dipole moment in the second excited state; UV spectra; quantum-mechanical characterization

THE 1600 Å BAND SYSTEM OF AMMONIA

1961 ◽  
Vol 39 (4) ◽  
pp. 479-501 ◽  
Author(s):  
A. E. Douglas ◽  
J. M. Hollas
Keyword(s):  
Excited State ◽  
High Resolution ◽  
Electronic State ◽  
Band System ◽  
Excited Electronic State ◽  
Degenerate State ◽  
Coriolis Interaction ◽  
Plane Vibration ◽  
Vibrational Levels ◽  
Out Of Plane

The progression of ammonia bands which extends from 1689 to 1400 Å has been photographed in absorption at high resolution. Six bands have been analyzed and found to be of the perpendicular type. The analysis shows that the molecule is planar in the excited state and that vibrational levels observed in the progression are those of the out-of-plane vibration. The excited electronic state is of the E′′ type. In addition to the normal Coriolis interaction of the degenerate levels, a second effect has been observed which behaves like the Coriolis interaction recently described as 'giant l-type doubling' by Garing, Nielsen, and Rao. No clear evidence has been found for any distortion of the degenerate state from D3h symmetry.

Molecular Modelling of Ground- and Excited-States Vibrations in Organic Conducting Devices: Hexakis(n-hexyloxy)triphenylene (HAT6) as Case Study

2010 ◽  
Vol 63 (3) ◽  
pp. 388 ◽  
Author(s):  
M. Zbiri ◽  
M. R. Johnson ◽  
L. Haverkate ◽  
F. M. Mulder ◽  
G. J. Kearley
Keyword(s):  
Excited State ◽  
Electronic State ◽  
Ground State ◽  
Density Functional ◽  
Excited Electronic State ◽  
Molecular Vibrations ◽  
Functional Theory ◽  
Model Calculations ◽  
Insight Into

In order to gain insight into fundamental aspects of organic photocell materials, we have calculated ground and excited electronic-state structures and molecular vibrations for an isolated HAT6 molecule (hexakis(n-hexyloxy)triphenylene). Excited-state calculations are carried out using time-dependent density functional theory and frequencies are evaluated analytically using coupled perturbed Kohn–Sham equations. These model calculations have been validated against new infrared and ultraviolet data on HAT6 in solution. The main allowed valence excitation, having the largest oscillator strength, is chosen for the structural and vibrational investigations. Comparison with the ground-state vibrational dynamics reveals surprisingly large spectral differences. In addition, the alkoxy tails, which are usually considered to play only a structural role, are clearly involved in the molecular vibrations and the structural distortion of the excited electronic state compared with the ground state. The tails may play a more important role in charge separation, transport and excited-state relaxation than was previously thought. In this case, chemical modification of the tails would allow vibrational and related properties of organic photocell materials to be tailored.

scholarly journals Imaging the Renner–Teller effect using laser-induced electron diffraction

2019 ◽  
Vol 116 (17) ◽  
pp. 8173-8177 ◽  
Author(s):  
Kasra Amini ◽  
Michele Sclafani ◽  
Tobias Steinle ◽  
Anh-Thu Le ◽  
Aurelien Sanchez ◽  
...  
Keyword(s):  
Excited State ◽  
Electron Diffraction ◽  
Electronic State ◽  
Geometric Structure ◽  
Structural Information ◽  
Excited Electronic State ◽  
Teller Effect ◽  
Rotational Spectroscopy ◽  
Pump Probe ◽  
Electronically Excited

Structural information on electronically excited neutral molecules can be indirectly retrieved, largely through pump–probe and rotational spectroscopy measurements with the aid of calculations. Here, we demonstrate the direct structural retrieval of neutral carbonyl disulfide (CS2) in theB∼1B2excited electronic state using laser-induced electron diffraction (LIED). We unambiguously identify the ultrafast symmetric stretching and bending of the field-dressed neutral CS2molecule with combined picometer and attosecond resolution using intrapulse pump–probe excitation and measurement. We invoke the Renner–Teller effect to populate theB∼1B2excited state in neutral CS2, leading to bending and stretching of the molecule. Our results demonstrate the sensitivity of LIED in retrieving the geometric structure of CS2, which is known to appear as a two-center scatterer.

Initial excited-state structural dynamics of 2′-deoxyadenosine

2019 ◽  
Vol 97 (6) ◽  
pp. 406-412 ◽  
Author(s):  
Swaroop Sasidharanpillai ◽  
Adam A. Friedman ◽  
Glen R. Loppnow
Keyword(s):  
Excited State ◽  
Electronic State ◽  
Structural Dynamics ◽  
Excited Electronic State ◽  
Resonance Raman ◽  
Photochemical Reactions ◽  
Spontaneous Breaking ◽  
Quantum Yields ◽  
Dna And Rna ◽  
Ultraviolet Resonance Raman

Purine nucleobases (adenosine and guanosine) are prone to spontaneous breaking of the nucleosidic bond to form abasic sites in both DNA and RNA. However, the purines also undergo photochemical reactions, including oxidation and cycloaddition, to form damage sites, albeit at lower photochemical quantum yields than the pyrimidines. In this study, we use ultraviolet resonance Raman spectroscopy to measure the initial excited-state structural dynamics in the nucleoside, 2′-deoxyadenosine. The resonance Raman-derived initial excited-state structural dynamics throughout the 260 nm La excited electronic state of adenine are found to be smaller in the nucleoside than in the previously reported 9-methyladenine nucleobase derivative, consistent with what is found for the pyrimidines thymine and uracil. Interestingly, resonance-enhanced vibrational modes in this electronic state also contain internal coordinates localized on the sugar, which may represent a different energy dissipation mechanism than in the pyrimidine nucleosides. The results will be discussed in terms of the initial excited-state photophysics and photochemistry of DNA and RNA.

scholarly journals The flame spectrum of carbon monoxide

1940 ◽  
Vol 176 (967) ◽  
pp. 505-521 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Electronic State ◽  
Excited Electronic State ◽  
Combustion Process ◽  
Wave Number ◽  
Band Spectrum ◽  
Liquid Form ◽  
Triangular Form ◽  
Reduced Pressure

The spectrum of the flame of carbon monoxide burning in air and in oxygen at reduced pressure has been photographed on plates of high contrast which display the band spectrum clearly above the continuous background. Greater detail has been obtained than has been recorded previously and new measurements are given. The structure of the spectrum has been studied systematically. It is shown that the bands occur in pairs with a separation of about 60 cm. -1 , this separation being due probably to the rotational structure. Various wave-number differences are found to occur frequently, and many of the strong bands are arranged in arrays using intervals of 565 and 2065 cm. -1 . The possible origin of the spectrum is discussed. The choice of emitter is limited to a polyatomic oxide of carbon, of which carbon dioxide is the most likely. The spectrum of the suboxide C 3 O 2 shows some resemblance to the flame bands, but this molecule is improbable as the emitter on other grounds. A peroxide C0 3 is also a possibility, but no evidence for the presence of this has been obtained from experiments on the slow combustion of carbon monoxide. Carbon dioxide in gaseous or liquid form is transparent through the visible and quartz ultra-violet, and the flame bands are not obtained from CO 2 in discharge tubes. Comparison with the Schumann-Runge bands of oxygen shows that it is possible that the flame bands may form part of the absorption band system of CO 2 which is known to exist below 1700 A if there is a big change in shape or size of the molecule in the two electronic states. The electronic energy levels of CO 2 are discussed. Since normal CO 2 is not built up from normal CO and oxygen, an electronic rearrangement of the CO 2 must occur after the combustion process. Mulliken has suggested that the molecule in the first excited electronic state, corresponding to absorption below 1700 A, may have a triangular form. The frequencies obtained from the flame bands are compared with the infra-red frequencies of CO 2 . The 565 interval may be identified with the transverse vibration v 2 , indicating that the excited electronic state is probably triangular in shape. The 2065 interval cannot, however, be identified with the asymmetric vibration v 3 with any certainty. If the excited electronic state of CO 2 is triangular, then molecules formed during the combustion by transitions from this level to the ground state may be “vibrationally activated”. This is probably the reason for many of the peculiarities of the combustion of carbon monoxide.

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