Electron impact spectra of silane and germane have been recorded using electrons of 200 eV incidence at scattering angles of sim;2deg;ndash;9deg;. The range of energy losses covers the entire region of single electron excitation from the valence shell. In the bound state spectrum evidence is presented supporting the existence of two valence transitions in addition to anticipateds,p, anddRydberg transitions. The 9deg; spectra reveal much structural detail in the sim;4 eV energy range preceding the2A1ion state. The most prominent band consists of a superposition of an optically allowed valence excitation and a symmetry forbidden Rydberg transition. The remaining peaks may be members of vibrational progressions belonging to either lsqb;d(t2),a1rsqb;, lsqb;p,a1rsqb;thinsp;larr;thinsp;(a1)2dipole allowed or lsqb;d(e),a1rsqb;, lsqb;s,a1rsqb;thinsp;larr;thinsp;(a1)2dipole forbidden channels. Of these two possibilities the evidence presented here favors the latter choice.
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