REMPI detection of alignment in NO collisions

Abstract

Abstract The detection of collision induced alignment in ensembles of NO molecules scattered from He or Ne is investigated. The alignment is probed through (2 + 1) resonance enhanced multiphoton ionization of NO via different Rydberg states: E 2 Σ , F 2 Δ , and H 2 Σ , H ′ 2 Π . Transitions belonging to the first two electronic systems yield identical polarization effects consistent with the fact that the two-photon transition is characterized by a single second rank tensor component Z (2) ±1 . The electronic system involving the H-state is considerably more complicated because of the state mixing due to L-uncoupling and the simultaneous presence of zeroth and second rank tensor components for the two-photon transition. Alignment moments extracted from TOF spectra measured through different electronic systems are identical within the experimental uncertainty. The alignment is consistent with predictions of either the kinematic apse or the geometric apse models. These models indicate further that higher moments have a negligible influence on the polarization effect if the alignment is derived from spectra measured with laser light polarized parallel and perpendicular to the molecular beam axis.