Electric-field-enhanced predissociation of the NO molecule studied by the two-color resonant four-wave mixing spectroscopy

Two-color four-wave mixing spectroscopy is applied to the observation of the 7f Rydberg state (v=0) of NO. Under a static electric field, not only the decrease in intensity but also the shift and the broadening of the 7f–A (2Σ+) transition lines are observed for the first time. These observations are attributed to the enhanced predissociation caused by a Stark mixing of the Rydberg state with the dissociative continua. No electric field effect is observed for the 6f–A (2Σ+) transition, which suggests that the perturbing state of the 7f state is the continuum of the I (2Σ+) state converging to the N (2D)+O (3P) dissociation limit.