Search for exchange-antisymmetric states for spin-0 particles at the 10^-11 level

We set a new upper limit of 1.7×10-11 to the probability that two spin-0 16O nuclei are in forbidden exchange-antisymmetric states, testing the validity of fundamental principles of quantum mechanics. A newly designed difference-frequency spectrometer is used to look for the existence of these states. The experimental test was performed by tuning the spectrometer across a molecular transition of 12C16O2 belonging to the rovibrational band at 4.25 μm, connecting the forbidden states (0000,J = 25) and (0001,J = 26).