Abstract:

Jet cooled CN radical beam was formed by cold cathode DC discharge of CH3CNunder molecular beam conditions. The cylindrical cold cathode was placed between the skimmer and the nozzle to prevent the nozzle from being clogged by carbon particles. The pulsed photon counting LIF measurement was seriously jeopardized by the high intensive scattering laser light due to CN(B2Σ)'s short lifetime (70ns) and weak fluorescence. By using an attenuator to reduce laser intensity or a polaroid to reduce the scattering laser intensity, we obtained LIF spectra with good S/N ratio. With the theoretical simulaed spectra, the effects of laser p0larization on LIF were discussed and the relative populations of CN rotational and vibrational states were obtained.

Key words: CN radical, Laser ineuced fluorescence, Molecular beam, Polarization, Cold cathode DC discharge