The first experimental anion photoelectron spectrum of the chloride-carbon monoxide complex is presented in combination with supporting ab initio calculations at the MP2 level of theory. The calculations reveal a previously unreported minimum for the neutral radical, namely the van der Waals Cl center dot center dot center dot OC linear complex. The experimental spectral feature is assigned to transitions from a Cl center dot center dot center dot CO bent van der Waals complex to the linear Cl center dot center dot center dot CO neutral van der Waals radical. A stabilisation energy of 0.16 +/- 0.01 eV is determined from the spectrum which is in line with the predicted cluster binding energies of 3.5 kcal mol (1) (0.15 eV) for the anion complex. (C) 2011 Elsevier B. V. All rights reserved.