Photoionization of NO(A2Σ+,ν=0, N) at 226 nm:: ion-recoil momentum spectroscopy

We report the first observation of ion recoil induced by the ionization process for a molecule. The applicability of the method has been demonstrated by determining the beta(2) and beta(4) anisotropy parameters of the angular distributions of NO+ ions in the resonance-enhanced two-photon ionization of NO(X(2)Pi(1/2), v = 0, J) via the A(2)Sigma(+)(v* = 0, N*) state at 226 nm. An energy resolution in the range of 10 mueV is demonstrated. The method might prove to be particularly useful for studying complex ionization-fragmentation processes as they occur for example for superexcited molecules. (C) 2004 Elsevier B.V. All rights reserved.