THE CRYSTAL SPECTRUM OF PERYLENE

1961 ◽  
Vol 39 (3) ◽  
pp. 451-458 ◽  
Author(s):  
Robin M. Hochstrasser
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption ◽  
Weak Coupling ◽  
Room Temperature ◽  
Excited Level ◽  
Vibrational Structure ◽  
Factor Group ◽  
Electronic Band ◽  
Dipole Interactions ◽  
Induced Dipole

The electronic absorption spectrum of crystalline perylene has been examined in the spectral region 3000–4700 Å. The lowest energy electronic state of perylene has a large oscillator strength and the crystal spectrum deviates considerably from that calculated from a weak coupling (Davydov) model.The sublimation flakes were examined at room temperature and at the temperature of boiling nitrogen. The lowest energy crystal state was polarized along the crystallographic a-axis (Bu) and the factor group splitting of lowest vibrational envelope of the electronic band was 800 cm−1. The whole spectrum was more intense along the a- than along the b-axis of the crystal. These results are consistent with the notion that the crystal spectrum is derived from dipole-induced dipole interactions between molecular B2u levels of perylene and neighboring unexcited molecules. This assignment of the lowest excited level of perylene is in agreement with theory.The molecular vibrational structure is severely altered in the crystal and the observed crystal shift is much smaller than that predicted by the Davydov theory.

THE ABSORPTION SPECTRUM OF DIPHENYLENE IN THE NEAR-ULTRAVIOLET

1961 ◽  
Vol 39 (4) ◽  
pp. 765-772 ◽  
Author(s):  
Robin M. Hochstrasser
Keyword(s):  
Absorption Spectrum ◽  
Band Structure ◽  
Theoretical Prediction ◽  
Intensity Distribution ◽  
Room Temperature ◽  
Excited Level ◽  
Vibrational Structure ◽  
Infrared Band ◽  
Weak Absorption ◽  
Near Ultraviolet

The absorption spectrum of diphenylene has been measured in the vapor at a variety of temperatures, in solution at room temperature, and in an EPA rigid glass at 90 °K. From a consideration of the band structure and intensity distribution it was concluded that the weak absorption at 25,041 cm−1 (vapor; ƒ ≈ 10−3) is due to a symmetry-forbidden electronic transition. The theoretical prediction that the excited level is of species B1g was supported by the presence of a strong infrared band at 732 cm−1 corresponding to observed perturbing vibration of frequency 792 cm−1. The solution spectrum was found to exhibit a vibrational structure typical of a g–g forbidden excitation.

The electronic spectra of phenyl radicals

1965 ◽  
Vol 287 (1411) ◽  
pp. 457-470 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Electronic Absorption ◽  
Ground State ◽  
Electronic Spectra ◽  
Flash Photolysis ◽  
Visible Region ◽  
Electronic Configuration ◽  
Vibrational Structure ◽  
Fundamental Frequencies

An electronic absorption spectrum, attributed to phenyl, has been observed in the visible region with origin at 18 908 cm -1 after flash photolysis of benzene and halogenobenzenes. Similar spectra of fluoro, chloro and bromo phenyl are observed after flash photolysis of disubstituted benzenes. The vibrational structure of the phenyl spectrum has been analysed in terms of two fundamental frequencies at 571 and 896 cm -1 which correspond to the e 2 g and a 1 g frequencies of the B 2 u state of benzene. The ground state of phenyl has a π 6 n electronic configuration and the observed transition is interpreted as 2 A 1 → 2 B 1 resulting from a π → n excitation.

The Near-ultraviolet Absorption Spectrum of Diimide in Liquid Ammonia and its Decomposition between −65 and −38 °C

1974 ◽  
Vol 52 (13) ◽  
pp. 2513-2515 ◽  
Author(s):  
R. A. Back ◽  
C. Willis
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Room Temperature ◽  
Liquid Ammonia ◽  
Vibrational Structure ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
First Order ◽  
Rapid Decomposition ◽  
Near Ultraviolet

The near-ultraviolet absorption spectrum of diimide in liquid ammonia at −50 °C is shifted about 500 Å to the red compared with the gas-phase spectrum, with λmax = 4000 Å. The spectrum is also broadened and the vibrational structure largely obscured. It is suggested that hydrogen bonding is responsible for these changes.Diimide is much more stable in liquid ammonia between −65 and −38 °C than in the gas phase at room temperature. A first-order decay is observed with Arrhenius parameters of A = 1.9 × 103 s−1 and E = 6.6 kcal/mol; this is always preceded by a more rapid, higher-order initial decay which may be related to the rapid decomposition observed during vaporization.

Electronic absorption spectrum of the NCS free radical

1968 ◽  
Vol 46 (23) ◽  
pp. 2619-2631 ◽  
Author(s):  
R. N. Dixon ◽  
D. A. Ramsay
Keyword(s):  
Absorption Spectrum ◽  
Free Radical ◽  
Electronic Absorption Spectrum ◽  
Electronic Absorption ◽  
Vibronic Interaction ◽  
Absorption Bands ◽  
Electronic Band ◽  
Rotational Constants ◽  
Considerable Evidence ◽  
Vibronic Interactions

Absorption bands of NCS between 3300 Å and 4000 Å have been assigned to two electronic band systems, A(2Πi) – X(2Πi) with its origin at 26 054 cm−1, and B(2Σ+) – X(2Πi) with its origin at 26 844 cm−1. Rotational analyses have been carried out for the stronger bands, yielding rotational constants B0 = 0.2036 cm−1 (A state), B0 = 0.1906 cm−1 (A state), and B0 = 0.1969 cm−1 (B state). In addition to vibronic interactions within the two 2Πi states (Renner effect) there is considerable evidence for vibronic interaction between the A(2Πi) and B(2Σ+) states.

Ortho effects on the change in electronic absorption spectrum of pyridinium salts of saturated bromohydrocarbon

2009 ◽  
Vol 74 (5) ◽  
pp. 1084-1089 ◽  
Author(s):  
Jin-Ling Song ◽  
Li-Ming Gong ◽  
Shou-Ai Feng ◽  
Jiang-Hong Zhao ◽  
Jian-Feng Zheng ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Electronic Absorption ◽  
Pyridinium Salts

PYRIDINE N-OXIDE COMPLEXES OF ZIRCONYL, THORIUM, AND URANYL PERCHLORATES

1964 ◽  
Vol 42 (4) ◽  
pp. 856-860 ◽  
Author(s):  
P. Rama Murthy ◽  
C. C. Patel
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Visible Region ◽  
Lone Pair ◽  
Vibrational Structure ◽  
Uranyl Complexes ◽  
Bond Character

Pyridine N-oxide complexes having the composition ZrO(Py•O)6(ClO4)2, Th(Py•O)8(ClO4)4, and UO2(Py•O)5(ClO4)2 have been prepared. The infrared and electronic absorption spectra show that the bonding between the metal and pyridine N-oxide in the complexes has occurred by donation of the lone pair of p-electrons on oxygen to the metal, and that the π-bond character of NO group increases in the complexes as uranyl < thorium < zirconyl. The decrease in the vibrational structure of the UO22+ spectrum in the visible region indicates strong coordination of pyridine N-oxide to the uranyl group. The decomposition temperatures of zirconyl, thorium, and uranyl complexes are 307, 350, and 319 °C respectively.

Molecular Vibrations in the Exciton Theory for Molecular Aggregates. II. Dimeric Systems

1961 ◽  
Vol 14 (3) ◽  
pp. 344 ◽  
Author(s):  
EG McRae
Keyword(s):  
Absorption Spectrum ◽  
Perturbation Theory ◽  
Fluorescence Spectra ◽  
Numerical Calculations ◽  
Molecular Vibrations ◽  
Molecular Aggregates ◽  
Absorption And Fluorescence Spectra ◽  
Band Structures ◽  
Electronic Band ◽  
Electronic Band Structures

The theory of Part I of this series (McRae 1961) is developed in detail for dimeric systems. The simplest possible theory of the exciton states for a system of two non-rigid molecules is obtained through the use of perturbation theory. The theory makes possible the prediction of electronic band structures in absorption and fluorescence spectra as functions of the theoretical Davydov splitting for two rigid molecules. Numerical calculations are made for a dimer of a typical dye, and the results are compared with the observed absorption spectrum of the 1,1'-diethyl-2,2'-pyridocyanine iodide dimer.

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