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Multimode analysis of depolarization ratio dispersion and excitation profiles of seven Raman fundamentals from the haeme group in ferrocytochrome c
Author(s) -
SchweitzerStenner Reinhard,
Bobinger Ulrich,
Dreybrodt Wolfgang
Publication year - 1991
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250220205
Subject(s) - raman spectroscopy , multi mode optical fiber , excitation , depolarization ratio , resonance (particle physics) , chemistry , dispersion (optics) , depolarization , molecular physics , analytical chemistry (journal) , nuclear magnetic resonance , atomic physics , physics , optics , optical fiber , quantum mechanics , medicine , endocrinology , chromatography
Abstract Experimental data for depolarization ratio dispersion (DPD) and resonance excitation profiles (REPs) with high spectral resolution (20 cm −1 ) are provided for seven Raman fundamentals in the region between 1150 and 1650 cm −1 of the haeme spectrum from ferrocytochrome c. They cover the resonant region of the Q ‐band and the preresonant region of the B ‐band. A self‐consistent analysis of the depolarization ratio dispersion (DPD) and resonance excitation profiles (REPs) of these Raman lines is carried out by explicit consideration of multimode mixing. This is achieved by first formulating the Raman tensor in Loudon's formulation to fifth order for each mode, thus restricting the contribution of the fifth‐order term to the vibration itself and omitting multimode contributions. By fitting this expression to the DPDs and REPs of each Raman mode, one obtains coupling parameters which in the next step are inserted into the fifth‐order term of each mode. Thus one takes account of their contributions to multimode mixing. To account for contributions of lower frequency modes, an effective ‘helping rest mode’ was added to the multimode contributions. This procedure yields satisfactory fits to all data sets. The respective fits to the DPD and REP of the oxidation marker line at 1363 cm −1 reproduce also the corresponding REP and DPD in the resonant region of the B ‐band reported by Champion and Albrecht with a high degree of accuracy. The vibronic coupling parameters obtained are consistent with the weak coupling limit. Further, they confirm the validity of Gouterman's four‐orbital model for ferrocytochrome c.