Preparation of ions in selected rotational states by delayed pulsed field ionization

Abstract

A novel method of preparing ions in selected rovibronic states is presented. It is based on pulsed field ionization of long‐lived high‐nRydberg states lying just below the different rovibronic energy levels of the ion. The potential of the method is illustrated with the example of hydrogen: A clean population of H2 + ions is prepared in the X 2∑ g + (v +=2, N +=0, 1, 2, 3) states. The method ought to be applicable to the preparation of a wide range of small molecular ions in selected rotational states and opens new possibilities in the study of state‐to‐state ion–molecule reactions.