Rotationally resolved photoionization: Influence of the 4 sigma -> k sigmashape resonance on CO+(B (2)Sigma(+)) rotational distributions

We present experimental and theoretical results on rotational distributions of CO+(B (2)Sigma (+)) photoions. Rotational distributions were determined for both the v(+)=0 and v(+)=1 vibrational levels following photoionizatio n of cold (T(0)approximate to9 K) neutral CO target molecules. Data were ge nerated using dispersed ionic fluorescence over a wide range of photoelectr on kinetic energies, 0 less than or equal toE(k)less than or equal to 120 e V, which allows one to interrogate the ionization dynamics. This wide spect ral coverage permits illustrative comparisons with theory, and calculated s pectra are presented to interpret the data. In particular, the comparison b etween theory and experiment serves to identify the strong continuum resona nt enhancement at h nu (exc)approximate to 35 eV in the l=3 partial wave of the 4 sigma-->k sigma ionization channel, as this feature has profound eff ects on the ion rotational distributions over a wide range of energy. Secon d, there are differences between the rotational substructure for the v(+)=0 and v(+)=1 vibrational levels. All of the experimentally observed features and trends are reproduced by theory, and the consequences of these compari sons are discussed. (C) 2001 American Institute of Physics.