Freezing of NO gateway emission by a magnetic field and very long field-free lifetimes of perturbed NO(a 4Π) levels

The collision-induced emission from perturbed NO(B 2Π/a 4Π) (“gateway”) levels, previously studied by us using a beam/target gas cell configuration, was re-examined by crossing the NO(a 4Π) beam with a target gas jet. Moving the observation point along the primary beam, spatially resolved NO(B,v=0 and 3) gateway emission profiles were recorded. Two types of measurements were made: (a) Applying a magnetic field at the collision zone, the B, v=0 emission was quenched within the field, but reappeared at the field exit. This “freezing” confirms the mechanism of the gateway quenching as formulated earlier. (b) In the absence of a magnetic field, anomalously long radiative lifetimes were determined from both the v=0 and v=3 emission profiles. This direct observation of the long-lived eigenstate resulting from the perturbation is consistent with earlier measurements on the other, short-lived component.