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Hybrid femtosecond/picosecond coherent anti‐Stokes Raman scattering for high‐speed CH 4 /N 2 measurements in binary gas mixtures
Author(s) -
Engel Sascha R.,
Miller Joseph D.,
Dedic Chloe E.,
Seeger Thomas,
Leipertz Alfred,
Meyer Terrence R.
Publication year - 2013
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.4261
Subject(s) - mole fraction , picosecond , raman scattering , femtosecond , analytical chemistry (journal) , raman spectroscopy , chemistry , excitation , coherent anti stokes raman spectroscopy , laser , atomic physics , optics , molecular physics , physics , chromatography , quantum mechanics
Hybrid femtosecond/picosecond (fs/ps) vibrational coherent anti‐Stokes Raman scattering was demonstrated for high‐speed, in‐situ measurements of CH 4 /N 2 mole fractions in binary gas mixtures with temporal nonresonant suppression. A single broadband, 100‐fs laser source was used to simultaneously excite CH 4 and N 2 vibrational Raman transitions, characterized by a spectral separation of ~584 cm −1 , followed by frequency‐domain detection with a time‐delayed ps probe pulse. In this manner, the temporal evolution of the nonresonant background and vibrational wavepackets of CH 4 and N 2 could be evaluated to maximize signal and minimize interferences. A typical accuracy of ~95% was achieved for experimental CH 4 mole fractions between 0.02 and 0.70, and a precision of ~4% was achieved by maximizing relative excitation energy through induced chirp in the pump and Stokes pulses. It was further shown that mole‐fraction measurements were not affected by variations in bi‐molecular broadened linewidths over a wide range of mixture fractions. Copyright © 2013 John Wiley & Sons, Ltd.