Nanosecond Flash Photolysis and the Absorption Spectra of Excited Singlet States

Nature ◽  
1968 ◽  
Vol 220 (5173) ◽  
pp. 1228-1229 ◽  
Author(s):  
GEORGE PORTER ◽  
MICHAEL R. TOPP
Keyword(s):  
Absorption Spectra ◽  
Flash Photolysis ◽  
Excited Singlet ◽  
Singlet States ◽  
Excited Singlet States

Enhanced basicity of 1,3-dialkoxy-substituted benzenes: cyclophane derivatives

1994 ◽  
Vol 72 (12) ◽  
pp. 2388-2395 ◽  
Author(s):  
Guangzhong Zhang ◽  
Yijian Shi ◽  
Renée Mosi ◽  
Thao Ho ◽  
Peter Wan
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Structural Constraints ◽  
Excited Singlet ◽  
Deuterium Incorporation ◽  
Stable Conformation ◽  
Substituted Benzenes ◽  
Singlet States ◽  
Excited Singlet States

The photoprotonation of four dialkoxy-substituted benzenes in their excited singlet states has been studied. The parent systems 4 and 5 are regioselectively photoprotonated at the 2-position, with significant quantum efficiencies for deuterium incorporation at acidities greater than pH 2. The structurally related cyclophane derivatives 6 and 7 did not show any deuterium exchange over the same acidity range but fluorescence quenching by proton (in aqueous solution) and laser flash photolysis studies (in 1,1,1,3,3,3-hexafluoro-2-propanol) indicate that photoprotonation does take place with these compounds. Due to structural constraints imposed by the most stable conformation adopted by these molecules (6 and 7), the attacking proton (deuteron) is also the proton (deuteron) that is deprotonated from the cyclohexadienyl cation (2,6-dialkoxybenzenonium ion) intermediate, resulting in the absence of incorporation of deuterium.

Zur Schwingungsstruktur der Shpolskii-Spektren von Naphthalin in n-Pentan bei 77 K (Fluoreszenz, S0 → S1- und S0 → S2-Absorption) *

1981 ◽  
Vol 36 (7) ◽  
pp. 705-712 ◽  
Author(s):  
P. Bałuk ◽  
A. Kawski ◽  
M. Kałas
Keyword(s):  
Absorption Spectra ◽  
Excited Singlet ◽  
Normal Coordinates ◽  
Pi Method ◽  
Singlet States ◽  
Condon Factors ◽  
Excited Singlet States ◽  
Franck Condon ◽  
Equilibrium Geometries

Abstract The fluorescence, So -> Si-and So -> S2-absorption spectra of naphthalene in n-pentane at 77 K were measured. The Franck-Condon-Factors are evaluated using equilibrium geometries and normal coordinates of the molecule in the ground (So), in first (Si) and secound (S2) excited singlet states which were calculated by the QCFF/PI-method and by taking the Dushinskii-Efekt into acount. These results were compared with experimentally determined frequencies and estimated relative intensities.

Nanosecond flash photolysis

1970 ◽  
Vol 315 (1521) ◽  
pp. 163-184 ◽  
Keyword(s):  
Flash Photolysis ◽  
Pulsed Laser ◽  
Triplet States ◽  
Excited Singlet ◽  
Excited Triplet ◽  
Singlet States ◽  
Time Region ◽  
Excited Singlet States ◽  
Chemical Events ◽  
Excited Triplet States

A flash photolysis system, using a pulsed laser as source, has been designed and used to study events having a duration of a few nanoseconds; an improvement over conventional flash techniques by a factor of a thousand. The apparatus incorporates both spectrographic and photoelectric monitoring techniques which are easily interchangeable and, apart from the laser itself, it is readily constructed from standard components. Its applications to the observation of the absorption spectra of excited singlet states, short-lived excited triplet states and chemical events in the nanosecond time region are described.

Quasiparticle Excitations in Polyenes and Polyacetylene

1987 ◽  
Vol 109 ◽  
Author(s):  
Paul Tavan ◽  
Klaus Schulten
Keyword(s):  
Dispersion Relations ◽  
Excited Singlet ◽  
Quasi Particle ◽  
Double Excitation ◽  
Singlet States ◽  
Excited Singlet States ◽  
Electron Excitations ◽  
Quasiparticle Excitations

ABSTRACTWe apply the Pariser-Parr-Pople Hamiltonian to study many-electron excitations in polyenes and polyacetylene. The excited singlet states of polyenes, calculated by a multireference double excitation expansion, are classified as quasi-particle excitations, namely as triplet-triplet magnons and particle-hole excitons. From finite polyene spectra we derive approximate dispersion relations for these quasi-particles in the infinite polyene, i.e. polyacetylene.

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