Photoionization of NO(A2Σ+, v=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 b2 and b4 anisotropy parameters of the angular distributions of NO þ ions in the resonanceenhanced two-photon ionization of NO(X 2 P1=2, v ¼ 0; J ) via the A 2 R þ (v � ¼ 0, N � ) state at 226 nm. An energy resolution in the range of 10 leV is demonstrated. The method might prove to be particularly useful for studying complex ionization-fragmentation processes as they occur for example for superexcited molecules. 2004 Elsevier B.V. All rights reserved.