Vibrational spectroscopy of shock compressed condensed phase nitrous oxide: Frequency shifts in the ν1 mode

Abstract

Over many years, we have published vibrational spectra of molecular materials at extreme pressure and temperature obtained using shock compression and coherent Raman spectroscopy methods. For diatomic molecules, we were able to extract vibrational temperatures from the intensities of spectrally resolved vibrational hot bands. Larger molecules in the condensed phase suffer band broadening effects that obscure the vibrational hot bands as the anharmonicities are typically smaller than the widths of the bands. This inability to resolve the hot bands inhibits the extraction of vibrational temperature and the measurement of the vibrational frequency of the fundamental. Here, we use a hot band model based on gas-phase anharmonic coupling coefficients to fit coherent anti-Stokes Raman spectra of the ν1 vibrational mode of shock compressed condensed phase N2O with shock pressures and temperatures estimated from literature equations of state and compare to fits from a model using a single Gaussian peak. We report the resulting vibrational frequency shifts with shock pressure.