scholarly journals Internal Rotation of the Methyl Group in the Electronically Excited State: o- and m-Toluidine

1987 ◽  
Vol 7 (2-4) ◽  
pp. 197-212 ◽  
Author(s):  
Katsuhiko Okuyama ◽  
Naohiko Mikami ◽  
Mitsuo Ito
Keyword(s):  
Excited State ◽  
Internal Rotation ◽  
Barrier Height ◽  
Ground State ◽  
Electronic Excitation ◽  
Vibrational Analysis ◽  
Fluorescence Excitation ◽  
Close Relationship ◽  
Electronically Excited ◽  
Dispersed Fluorescence

The fluorescence excitation and dispersed fluorescence spectra of jet-cooled o- and m-toluidine were observed. Vibrational analysis of the spectra provided us with the potentials for the internal rotation of the CH3 group in both ground and excited states. In o-toluidine, a large potential barrier to the internal rotation in the ground state is practically removed in the excited state. On the other hand, a nearly free internal rotation of the CH3 group in the ground state of m-toluidine gains a large barrier by the electronic excitation. The great change in the barrier height upon the electronic excitation is more remarkable than that found for fluorotoluene. A close relationship between the barrier height and the π electron density at the ring carbon atom was found, indicating the hyperconjugation as the origin of the barrier height in the absence of steric hindrance.

Vibrational Analysis of the 2800 Å Band System of para-Dibromobenzene

1972 ◽  
Vol 50 (12) ◽  
pp. 1402-1408 ◽  
Author(s):  
S. M. Japar
Keyword(s):  
Excited State ◽  
High Resolution ◽  
Ground State ◽  
Band System ◽  
Vibrational Analysis ◽  
Type A ◽  
Strong Type ◽  
Type B ◽  
Sequence Structure ◽  
Extensive Sequence

The 2800 Å band system of p-dibromobenzene has been photographed under high resolution and an extended vibrational analysis has been carried out. The analysis is not inconsistent with the assignment of the system to a 1B2u ← 1Ag transition, by analogy with other p-dihalogenated benzenes. The observed spectrum can be explained in terms of a number of strong type-B vibronic bands and a considerably smaller number of type-A vibronic bands. The extensive sequence structure is adequately accounted for, and can be related to observations on other halogenated benzene molecules. Thirteen ground state and nine excited state fundamental vibrational frequencies have been assigned.

scholarly journals Methyl Internal Rotation Fine Structure in the Ground State Rotational Spectrum of Gauche Butane

1990 ◽  
Vol 45 (8) ◽  
pp. 989-994 ◽  
Author(s):  
Kirsten Vormann ◽  
Helmut Dreizler ◽  
Hans Hübner ◽  
Wolfgang Hüttner
Keyword(s):  
Fine Structure ◽  
Internal Rotation ◽  
Barrier Height ◽  
Ground State ◽  
High Accuracy ◽  
Rotational Spectrum ◽  
Frequency Range ◽  
Vibrational Ground State ◽  
Rotation Parameters

Abstract The methyl torsional fine structure in the rotational spectrum of gauche butane in the vibrational ground state was investigated in the frequency range between 10 and 141 GHz. Using the internal axis method (IAM) in the formulation of Woods, all internal rotation parameters were determined with high accuracy. The barrier height of the methyl internal rotation was determined to 11.34 (29) kJ/mol (2.710 (69) kcal/mol)

The electronic spectrum of nitrosomethane, CH 3 NO

1965 ◽  
Vol 283 (1394) ◽  
pp. 423-432 ◽  
Keyword(s):  
Excited State ◽  
Electronic Spectrum ◽  
Ground State ◽  
Electronic Excitation ◽  
Flash Photolysis ◽  
Vibrational Features

A spectrum of a metastable molecule has been observed in the region 6000 to 7100 Å after flash photolysis of t -butyl nitrite. The analysis of this spectrum strongly suggests that the absorption is due to a π * — n (N) transition of nitrosomethane, and that the largest geometry change on electronic excitation is an increase by about 8° in the CNO angle. Unusual vibrational features in this spectrum are interpreted in terms of a decrease in the barrier to torsion of the CH 3 group about the CN bond from 940 ± 200 cm -1 in the ground state to 290 ± 50 cm -1 in the excited state.

scholarly journals Solvent-Dependent Resonance Raman Excitation Profiles of 9,9'-Bianthryl

1999 ◽  
Vol 19 (1-4) ◽  
pp. 51-56
Author(s):  
Gregory D. Scholes ◽  
Thierry Fournier ◽  
David Phillips ◽  
Anthony W. Parker
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Ground State ◽  
Electronic Excitation ◽  
Electronic Absorption Spectra ◽  
Excited Electronic State ◽  
Resonance Raman ◽  
Initial State ◽  
Solvent Environment ◽  
Raman Excitation Profiles

Dynamics subsequent to the electronic excitation of 9,9′-bianthryl produce a polar emissive excited state for which the symmetry of the bichromophore is broken by a dynamic solvent stabilisation of one of the two, otherwise degenerate, charge transfer configurations which contribute to the excited electronic state. The initial state created upon excitation is examined here by analysis of ground state resonance Raman excitation profiles (REPs) and electronic absorption spectra in solvents of various polarities. The results suggest that the REPs are signalling electronic differences between the initially excited state in the various solvents. We suggest that this is related to the bianthryl excited state being responsive to the disordered solvent environment.

Sign in / Sign up

Export Citation Format

Share Document