VIBRATIONAL-SPECTRUM OF LIQUID NITROMETHANE REVISITED USING POLARIZATION-SENSITIVE COHERENT ANTI-STOKES-RAMAN SCATTERING (PCARS) SPECTROSCOPY

Polarization-sensitive coherent anti-Stokes Raman scattering (PCARS) s pectroscopy was applied for the first time for detailed analyses of vi brational resonances of neat liquid nitromethane in the spectral range 900-1500 cm-1. The polarization PCARS properties show that the main t otally symmetric band v4 at 917 cm-1 and its observed symmetry on the lower wavenumber side (previously assigned to hot bands) are in fact t wo different bands. The origin of this observed asymmetry in the lower wavenumber side of the totally symmetric vibrational mode v4 is then discussed. Spectroscopic parameters (wavenumbers, bandwidth, polarizat ion ratio, etc.) of vibrational spectra are then determined precisely for complex spectral bands of neat liquid nitromethane taking into acc ount unique PCARS properties.