High‐resolution stimulated Raman spectroscopy and analysis of the ν 1 /ν 5 (C–H) stretching dyad of C 2 H 4

The high‐resolution stimulated Raman spectra of the ν 1 / ν 5 C–H stretching bands of C 2 H 4 have been recorded and analyzed by means of the tensorial formalism developed in Dijon for X 2 Y 4 asymmetric‐top molecules. A total of 689 lines (428 for ν 5 and 261 for ν 1 ) were assigned and fitted as a dyad including Coriolis coupling constants. We obtained a global root mean square deviation of 4.39 × 10 − 3 cm − 1 (4.61 × 10 − 3 cm − 1 for ν 1 , 4.25 × 10 − 3 cm − 1 for ν 5 ). The nearby 2 ν 2 band, extrapolated from ν 2 , was included in the analysis. However, no interaction parameter involving it could be fitted. The analysis is quite satisfactory, although some parts of ν 5 are not very well reproduced, probably indicating some yet unidentified resonances. This region is indeed quite dense, with many interacting dark states that cannot be included at present. Copyright © 2012 John Wiley & Sons, Ltd.