The CN free radical in acetonitrile discharges

Infrared diode laser absorption, Fourier-transform infrared (FTIR) and optical emission spectroscopies have been applied to the study of the CN radical and other transient species in acetonitrile/argon plasmas. A dc discharge was used to produce the CN radical in which both the infrared rovibrational spectrum around 2000 cm-1 and the B-X electronic emission spectrum around 388 nm were detected. The concentration of CN was determined to be in the region of 1011-1012 cm-3, aided by vibrational intensity calculations performed at UB3LYP/6-311+G** level of theory in Gaussian 98. An acetonitrile plasma was also generated in a static cell and by using FTIR spectroscopy; the main product observed under such conditions was HCN. Based on the experimental data, it appears that the major reaction pathways for CN in the plasma involve electron impact dissociation and excitation processes and its reaction with HCN. In order to provide a better overall understanding of the gas phase reaction pathways in the plasma, emission studies of excited NH, C2 and CH generated in the same plasma were performed as well