Abstract
The symmetrization postulate (SP) is regarded as the foundation of quantum mechanics. It stated that wavefunction of bosons must be symmetry, and fermions' must be anti-symmetry with respect to exchange of two identical particles. Recently, there were some theories predicted the possible violation of symmetrization postulate. In order to verify these predictions, the existence of the absorption lines forbidden by the SP is searched by high sensitive spectroscopic method. We use a tunable single-frequency mid-infrared PPLN (periodically poled lithium niobate) DFG (Difference Frequency Generation) source and a multi-pass absorption cell to search the forbidden exchange-antisymmetric line 0001-0000 R(25) of carbon dioxide spectrum. The DFG source is pumped by a single frequency Nd:YAG laser (1 W, 1064 nm) and a single frequency Ti:Sapphire laser (1.8 W, 780~870 nm). The Ti:Sapphire laser is frequency locked on the hyperfine structure of iodine molecule to reduce the frequency drift of the DFG source. We determine the upper limit of symmetry-violation parameter with a nearby SP allowed weak absorption line 0221-0220 R(80). For the purpose of increasing the sensitivity, we use cyclic average method to eliminate the fringe due to the optical interference of the multi-pass absorption cell. Furthermore, we average the results of 688 scans to reduce the noise. We have pushed the upper limit of symmetry-violation parameter to . To our knowledge, our result was two order lower than previous works. In the future, we will further improve the upper limit by reduce the drift of DFG source. This research is important for the fundamental of quantum mechanics.