Electric deflection studies of metastable acetylene

Abstract

Molecular beams of a metastable electronic state of acetylene are prepared by electron impact excitation. The threshold for appearance of the state is near 4.5 eV. Electric deflection measurements of C₂H₂, C₂D₂, and HC₂D show the polarity of all three isotopes to be below the level of detectability. Comparison of the behavior of the metastable state with that of the ground electronic state of HC₂D, where polarity is readily established by electric deflection, is made. The polarity results are shown to establish a trans geometry for the observed state.