(1+1) REMPI spectroscopy and high-level ab initio study of the complex formed between NO and CO

A molecular complex between NO and CO has been observed for the first time. The results of two studies are reported: the (1 + 1) REMPI spectrum of the Ã←X̃ transition and the results of high-level ab initio calculations [RCCSD(T)/aug-cc-pVQZ//UQCISD/6-311+G(3df)] on the X̃2Π state. The indications are that the complex is composed of two close-to-freely rotating diatoms. Comparison of the spectrum and the results of the ab initio calculations suggests that the lowest energy isomer of the complex is not observed, or that possibly more than one isomer is present in the experiment.