A mass spectrometric and laser spectroscopic experiment has been performed to characterize reactive species that are formed in a supersonic planar plasma expansion generated by discharging a high-pressure gas pulse in a multi-layer slit nozzle geometry. Discharges through mixtures of nitrogen, water and acetylene in He have been studied. The mass spectrometric study uses a state-of-the-art time-of-flight setup. Besides (cluster) cations, with sizes as large as (H 2 O) 56 H + , a variety of pure carbon chain anions has been observed. The spectroscopic study uses cavity ring down spectroscopy and shows that a planar plasma is also suited to obtain rotationally resolved spectra of vibrationally excited metastable electronic states.

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Time-of-¯ight mass spectra generated by ArF laser photoionization have been obtained in a molecular beam effusing from an a-Si:H deposition system with a dc discharge in a gas mixture of SiH 4 and He. The XeF, KrF, and ArF laser wavelength dependence and the kinetics of the SiH 0À3 and the Si 2 H 0À2 signals show that the ions predominantly originate from disilane.

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