Isomer separation of bis(trifluoromethyl)benzene by use of mid-infrared free electron laser

We have demonstrated the possibility of the isomer separation by means of the multi-photon dissociation induced by the irradiation with FEL light, by using a gaseous mixture of 1,3- and 1,4-bis(trifluoromethyl)benzene as the sample. The both isomers have CF3 antisymmetric stretching vibration mode at 1284 cm−1 for the 1,3-isomer and 1324 cm−1 for the 1,4-isomer. By the irradiation of FEL light to the mixture at the power of 14 mJ, the multiphoton dissociation (MPD) of the mixture has occurred effectively. We have obtained the MPD spectrum of the mixture in the frequency region from 1333 to 1253 cm−1. At the frequency region lower than 1290 cm−1, the 1,3-isomer was mainly dissociated and the selectivity of the dissociation exceeded 100 when the FEL frequency was tuned to 1253 cm−1.