AbstractA new ionization technique based on a modification of the conventional plasma‐desorption mass spectrometric apparatus is described. An electron avalanche produced by the microchannel plates of a secondary electron multiplier is found to desorb a sufficient amount of (quasi‐)molecular ions of non‐volatile thermally labile molecules. Spectra of several substances with molecular masses up to 1250 u are presented. The mechanism of electron avalanche desorption is now under investig