Vibrational spectrum of liquid nitromethane revisited using polarization-sensitive coherent anti-stokes Raman scattering (PCARS) spectroscopy
Résumé
Polarization-sensitive coherent anti-Stokes Raman scattering (PCARS) spectroscopy was applied for the first time for detailed analyses of vibrational resonances of neat liquid nitromethane in the spectral range 900–1500 cm−1. The polarization PCARS properties show that the main totally symmetric band ν4 at 917 cm−1 and its observed asymmetry on the lower wavenumber side (previously assigned to hot bands) are in fact two different bands. The origin of this observed asymmetry in the lower wavenumber side of the totally symmetric vibrational mode ν4 is then discussed. Spectroscopic parameters (wavenumbers, bandwidth, polarization ratio, etc.) of vibrational spectra are then determined precisely for complex spectral bands of neat liquid nitromethane taking into account unique PCARS properties.