Two-color studies of autoionizing states in small molecules

Two-color resonantly enhanced multiphoton ionization (REMPI) is used to study rotational autoionization of molecular hydrogen and nitric oxide. In contrast to conventional, single-photon techniques, the REMPI technique can be used to study autoionizing levels of H2 that can decay only through very weak interactions such as p-f mixing and singlet-triplet mixing. In addition, rotational autoionization that occurs with that change in rotational quantum number greater than 2 can also be examined (i.e., ΔN+>2). In homonuclear molecules, symmetry considerations require that ΔN+ be even; in heteronuclear molecules, ΔN+ may be even or odd. It is found, however, that NO is in some sense quasi-homonuclear, and that processes with ΔN+ = even appear to be more efficient than processes with ΔN+ = odd