CN Stretch Mode Research Articles

Investigation of Shock-Induced Chemical Decomposition of Sensitized Nitromethane Through Time-Resolved Raman Spectroscopy

AbstractMolecular processes associated with shock induced chemical decomposition of a mixture of nitromethane with ethylenediamine (0.1 wt%)are examined using time-resolved, Raman scattering. When shocked by stepwise loading to 14.2 GPa pressure, changes in the nitromethane vibrational modes and the spectral background characterize the onset of reaction. The CN stretch mode softens and disappears even as the NO2 and CH3 stretch modes, though modified, retain their identities. The shape and intensity of the spectral background also shows changes characteristic of reaction. Changes in the background, which are observed even at lower peak pressures of 11.4 GPa, are assigned to luminescence from reaction intermediates. The implications of these results to various molecular models of sensitization are discussed.

Infrared, Raman, and coherent anti-Stokes Raman spectroscopy of the hydrogen/deuterium isotopomers of nitromethane

The vibrational spectroscopy of the four hydrogen/deuterium isotopomers of nitromethane was investigated. Infrared, Raman, and coherent anti-Stokes Raman spectroscopy (CARS) of the isotopomers were used to determine vibrational frequencies for each isotopomer. Results for the d{sub 0}, d{sub 2}, and d{sub 3} isotopomers agree well with literature values. Gas- and liquid-phase spectra for the d{sub 1} isotopomer are presented, and the measured vibrational frequencies compare well with a theoretical prediction. In addition, high-resolution Raman spectra of the CN stretch mode were used to analyze the elements of the anharmonic coupling matrix involving this mode. Finally, the relative differential Raman scattering cross section of the Cn stretch mode of each isotopomer was determined.

HREELS of cyanogen on Pd(111)

Cyanogen (NCCN) adsorbs molecularly on Pd(111) between 120 and 250 K. The C-C stretch vibration (105 meV) persists when the sample is heated to 250 K. Above 250 K, cyanogen is dissociated; three peaks are observed; Pd-CN (37 meV), and CN stretch modes (225, 237 meV) that are attributed to successively filled adsorption sites. The CN stretch losses are weak, approximately 0.1 % of the elastic peak intensity. No further fragmentation of CN is observed. At 120 K, cyanogen adsorbs in multilayers. At 1×E-7 torr constant cyanogen back pressure, the CN stretch vibrations (261, 283 meV) are 0.1 % of the elastic intensity. At monolayer coverage, the lattice (bending) modes are dominant (30, 60 meV). At room temperature, Pd(111) converts NCCN to HCN by the reaction CN(ads) + H(ads) = HCN(ads) where the HCN is rehybridized to a CN double bond (190 meV). Comparison of HREEL spectra of cyanogen with those of the CN ring compound s-tri-azine make the possibility of polymerization of CN to a “paracyanogen” unlikely.

Librational and Phonon Sidebands of the Infrared CN Stretching Mode in NaCN and KCN Crystals

Librational and Phonon Sidebands of the Infrared CN Stretching Mode in NaCN and KCN Crystals