A new spectral emission source of rotationally cooled molecular ions. Application to supersonic expansions of CO and CO2 gases

A new emission source for the spectroscopy of rotationally cooled molecular ions has been developed in which a Penning-type electric discharge is established through a supersonic free jet. CO and CO2 gases were used to test its working conditions. Several previously unobserved emission bands were identified, among them one that probably originates from the CO2+ ion. Moreover, anomalous rotational intensity distributions in the CO+ B-X emission observed from the excitation of rotationally cooled CO2 suggest the existence of a dissociative bent electronic state in the CO2+ ion.