The absolute dissociative-electron-attachment cross section for ${\mathrm{O}}_2$ condensed on a Kr film is found to be about 20 times larger than that for gaseous ${\mathrm{O}}_2$. This large enhancement is attributed to a downward energy shift (≊0.9 eV) of the ${\mathrm{O}}_2^{\mathrm{-}}$ ${(}^2$${\mathrm{\Pi }}_{\mathrm{u}}$) intermediate state due to electronic polarization of the neighboring Kr atoms. Based on the theory developed by O’Malley [Phys. Rev. 150, 14 (1966)] and 155, 59 (1967)], we have shown that this downward shift increases the dissociative attachment by a factor of about 21, through a reduction in the autoionization of the intermediate state.

• Received 23 October 1989

DOI:https://doi.org/10.1103/PhysRevLett.64.523