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Ab initio calculations of the ultraviolet resonance Raman spectra of uracil
Author(s) -
Peticolas Warner L.,
Rush Thomas
Publication year - 1995
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540161008
Subject(s) - uracil , raman spectroscopy , ab initio , ultraviolet , resonance (particle physics) , computational chemistry , ab initio quantum chemistry methods , spectral line , resonance raman spectroscopy , chemistry , nuclear magnetic resonance , molecular physics , materials science , atomic physics , physics , molecule , optics , organic chemistry , quantum mechanics , optoelectronics , dna , biochemistry
An equation been derived to calculate, ab initio , the frequencies and intensities of a resonant Raman spectrum from the transform theory of resonance Raman scattering. This equation has been used to calculate the intensities of the ultraviolet resonance Raman spectra from the first π‐π* excited state of uracil and 1,3‐dideuterouracil. The protocol for this calculation is as follows: (1) The force constant matrix elements in Cartesian coordinate space, the vibrational frequencies, and the minimum energy ground and excited state geometries of the molecule are calculated ab initio using the molecular orbital program Gaussian 92, (2) the force constants in Cartesian coordinates are transformed into force constants in the space of a set of 3 N – 6 nonredundant symmetrized internal coordinates, (3) the G matrix is constructed from the energy minimized ground state Cartesian coordinates and the GFL = L Λ eigenvalue equation is solved in internal coordinate space, (4) the elements of the L and L −1 matrices are calculated, (5) the changes in all of the internal coordinates in going from the ground to the excited state are calculated, and (6) these results are used in combination with the transform theory of resonance Raman scattering to calculate the relative intensities of each of the 3 N – 6 vibrations as a function of the exciting laser frequency. There are no adjustable parameters in this calculation, which reproduces the experimental frequencies and intensities with remarkable fidelity. This indicates that the Dushinsky rotation of the modes in the excited state of these molecules is not important and that the simplest form of the transform theory is adequate. © 1995 John Wiley & Sons, Inc.