Ground and Electronically Excited Singlet-State Structures of 5-Fluoroindole Deduced from Rotationally Resolved Electronic Spectroscopy and ab Initio Theory

ChemPhysChem ◽  
2012 ◽  
Vol 13 (13) ◽  
pp. 3134-3138 ◽  
Author(s):  
Christian Brand ◽  
Olivia Oeltermann ◽  
Martin Wilke ◽  
Jörg Tatchen ◽  
Michael Schmitt
Keyword(s):  
Ab Initio ◽  
Singlet State ◽  
Electronic Spectroscopy ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Ab Initio Theory ◽  
Electronically Excited

Combined Experimental and Theoretical Study of the Transient IR Spectroscopy of 7-Hydroxyquinoline in the First Electronically Excited Singlet State

2016 ◽  
Vol 120 (47) ◽  
pp. 9378-9389 ◽  
Author(s):  
Felix Hoffmann ◽  
Maria Ekimova ◽  
Gül Bekçioğlu-Neff ◽  
Erik T. J. Nibbering ◽  
Daniel Sebastiani
Keyword(s):  
Ir Spectroscopy ◽  
Theoretical Study ◽  
Singlet State ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Electronically Excited

Violation of Hund's multiplicity rule in the electronically excited states of conjugated hydrocarbons

1985 ◽  
Vol 63 (7) ◽  
pp. 1572-1579 ◽  
Author(s):  
Shiro Koseki ◽  
Takeshi Nakajima ◽  
Azumao Toyota
Keyword(s):  
Triplet State ◽  
Excited States ◽  
Singlet State ◽  
Basis Set ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Electronically Excited States ◽  
Conjugated Hydrocarbons ◽  
Electronically Excited ◽  
Linear Polyenes

Violation of Hund's multiplicity rule in the electronically excited states of conjugated hydrocarbons is studied by using the Pariser–Parr–Pople type SCF MO method and the abinitio MO method with STO-3G basis set, both methods being augmented by CI-type treatments. It is shown that for symmetrical structures (D2h) of the nonalternant hydrocarbons, propalene, pentalene, and heptalene, the lowest excited singlet state is energetically lower than the corresponding triplet state. This is mainly due to the spin polarization (SP) effects. For D2h, structures of pentalene and heptalene the open-shell excited singlet state is predicted to be lower in energy than the closed-shell state, with the result that the former is really the ground state. Further, calculations made by including electron correlation effects reveal that in linear polyenes and polyacenes, the lowest excited singlet "minus" state (using Pariser's classification of the alternancy symmetry species) is lower in energy than the corresponding triplet state. The energy lowering of the singlet "minus" state in linear polyenes is due mostly to the mixing with the doubly excited configurations (mm → nn), while the considerable part of it in polyacenes is due to the SP effects.

The effect of temperature, pressure, and excitation wavelength on the photoluminescence of acetaldehyde vapour

1973 ◽  
Vol 333 (1594) ◽  
pp. 385-402 ◽  
Keyword(s):  
Vibrational Energy ◽  
Singlet State ◽  
Energy Content ◽  
Excited Singlet State ◽  
Effect Of Temperature ◽  
Excitation Wavelength ◽  
Triplet States ◽  
Excited Singlet ◽  
Vibrationally Excited ◽  
Electronically Excited

A study of the effect of acetaldehyde, trans -butene-2, and isobutane pressure on the fluorescence and phosphorescence emissions from acetaldehyde vapour has been made. The results have been interpreted in terms of electronically excited singlet and triplet states, in the behaviour of which vibrational energy content plays a crucial role. The extent to which the initially formed excited state undergoes predissociation, or is collisionally deactivated, has been examined from 254 to 340 nm between 20 and 99°C. At the longer excitation wavelengths the effect of pressure on emission yields indicates that collisional deactivation to the vibrationally equilibrated levels of the excited singlet state followed by intersystem crossing to the triplet state is the predominant mode for energy dissipation. At shorter excitation wavelengths predissociation becomes of increasing importance. Collisional deactivation of excited singlet acetaldehyde molecules by acetaldehyde and trans -butene-2 occurs by a single stage mechanism, in contrast to isobutane, and the possibility of complex formation is discussed. Relative rates for collisional deactivation by butene-2 and acetaldehyde of vibrationally excited acetaldehyde molecules in the first excited singlet state have been determined and shown to vary as a function of excitation wavelength.

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