Mode-dependent vibrational autoionization in aniline

High-resolution photoelectron spectroscopy is used to study the branching r atios for vibrational autoionization of Rydberg states of aniline (C6H5NH2) converging to the ground electronic state of the ion. By using two-color d ouble-resonance excitation, it is possible to prepare autoionizing resonanc es in which two different vibrational modes are excited. Determination of t he vibrational state distribution in the product ion provides information o n the relative rates of autoionization for the two modes. It is found that some normal modes appear to be especially effective at promoting vibrationa l autoionization, while others appear to be completely ineffective. (C) 200 0 American Institute of Physics. [S0021-9606(00)00834-5].