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Retrieval of spectral and dynamic properties from two‐dimensional infrared pump‐probe experiments
Author(s) -
Chelli Riccardo,
Volkov Victor V.,
Righini Roberto
Publication year - 2008
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.20901
Subject(s) - anharmonicity , dimension (graph theory) , convolution (computer science) , function (biology) , speedup , physics , statistical physics , algorithm , computational physics , computer science , mathematics , quantum mechanics , parallel computing , evolutionary biology , artificial neural network , pure mathematics , machine learning , biology
We have developed a fitting algorithm able to extract spectral and dynamic properties of a three level oscillator from a two‐dimensional infrared spectrum (2D‐IR) detected in time resolved nonlinear experiments. Such properties go from the frequencies of the ground‐to‐first and first‐to‐second vibrational transitions (and hence anharmonicity) to the frequency‐fluctuation correlation function. This last is represented through a general expression that allows one to approach the various strategies of modeling proposed in the literature. The model is based on the Kubo picture of stochastic fluctuations of the transition frequency as a result of perturbations by a fluctuating surrounding. To account for the line‐shape broadening due to pump pulse spectral width in double‐resonance measurements, we supply the fitting algorithm with the option to perform the convolution of the spectral signal with a Lorentzian function in the pump‐frequency dimension. The algorithm is tested here on 2D‐IR pump‐probe spectra of a Gly‐Ala dipeptide recorded at various pump‐probe delay times. Speedup benchmarks have been performed on a small Beowulf cluster. The program is written in FORTRAN language for both serial and parallel architectures and is available free of charge to the interested reader. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008