Observation of a Curve Crossing Mechanism in the Field Ionization of Inner-Shell Excited Single ${\rm Xe}^{33+}{(2\bar{\rm p})}$ and Double ${\rm Xe}^{34+}{(2\bar{\rm s}2\bar{\rm p})}$ Vacancy States

Anomalous intensity dependent quenching of the Xe(L) hollow atom emission from the single Xe
³³⁺
(2p̅) and double Xe
³⁴⁺
(2s̅2p̅) vacancy 3d→2p transition arrays indicates the presence of a state-selective curve crossing mechanism for the field ionization of the excited 3d
⁴
configuration by intense (2-3 × 10
²⁰
× W/cm
²
) 248-nm radiation.