Metastable excitations of large clusters of 3He, 4He, or Ne atoms

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Abstract
Metastable electronic states of helium clusters of 106 to 108 atoms of either isotope, or of neon clusters of some 104 atoms, are observed to be excited by the impact of electrons of 30 to 100 eV energy. Being detected through the release of electrons which results from the impact of the excited neutral or ionized clusters onto the first dynode of an electron multiplier, these metastable excitations allow the time‐of‐flight spectrometry of speeds and sizes of large clusters. The energy dependence of the excitation probability of the helium clusters indicates the initial excitation of the metastable atomic triplet state while the observed flight times of about 10−3 s point to the metastable triplet molecular state as the final helium cluster excitation.