Infrared Laser Spectrum of theSi2−Anion in a Silane Plasma

Abstract

The first rotationally resolved spectrum of the ${\mathrm{Si}}_2^{-}$ anion has been detected. The spectrum was recorded in a low pressure air cooled discharge in mixtures of silane and hydrogen producing amorphous silicon, using infrared laser velocity modulation absorption spectroscopy. Seventy lines between 740 and $820{\mathrm{cm}}^{-1\mathrm{}}$ were assigned to the $A^2{\Pi }_{u1/2\mathrm{}}(\upsilon =1\mathrm{})\leftarrow X{}_{}{}^2{}_{}{}^{}\Sigma _g^{+}{}_{}{}^{}(\upsilon =0\mathrm{})$ subband of ${\mathrm{Si}}_2^{-}$. A fit by standard Hamiltonians gives precise rotational and fine structure constants for the anion.