Abstract：

Carbon monoxide, CO, serves as the most important tracer to map molecular abundance in the universe. Furthermore, CO is involved in many physical, chemical and biological processes on Earth.  In order to observe and study processes involving CO in the laboratory, sensitive and quantitative experimental detection schemes for nascent CO are of obvious importance and much effort has therefore been spent in developing detection methods.  In this talk we will show that accidental secondary resonances can play an important role in resonance enhanced multiphoton ionization (REMPI) schemes used to detect CO; particularly in the most-used (2+1) REMPI schemes via the B 1Sigma and C 1Pi electronic states, but also in our newly developed VUV ionization scheme via the A 1Pi state at 154 nm.  In order to characterize the REMPI processes and accidental resonances we measure the ion-recoil of CO and use a non-skimmed pulsed valve expansion in the detection chamber in order to create rotationally warm but translationally cold CO molecule.  Applications include characterization of collision induced alignment during crossed-beam scattering of CO with noble gases, alignment of nascent CO following photodissociation of CO2 and OCS, and in the near future, scattering of CO from ice surfaces.