High Resolution Laser Spectroscopy Based On DFB-QCL And Pulsed Supersonic Molecular Beam And Its Applications

Distributed-feedback quantum cascade lasers?DFB-QCLs?in combination with a supersonic molecular beam expansion are a perfect tool for the investigation of molecules,ions and radicals at low temperatures,due to their high output power and near room temperature operation.Two experimental techniques have been developed for high resolution laser spectroscopy based on DFB-QCL and pulsed supersonic molecular beam:a continuous wave segmented rapid-scan scheme with a moderate vacuum pumping capacity and an intra-pulse rapid-scan scheme with a pulsed supersonic discharge jet.To demonstrate how powerful the combination of DFB-QCLs and a molecular beam expansion can be,we present some recent results rewere recorded by the continuous wave segmented rapid-scan scheme.Secondly,the observed spectrum corded by these two experimental schemes.Firstly,the jet-cooled absorption spectrum of HCOOH,HCOOD for monomers,?HCOOH?₂,HCOOH-HCOOD,?HCOOD?₂ for dimers and Ar-NO complex of HCOOH and HCOOD were fitted by the PGOPHER program and the unperturbed band origin and rotational constants in the excited vibrational state were determined for both HCOOH and HCOOD.Thirdly,the absorption spectrum signals produced by pulsed discharge jet of[Ne/O2/CH2I2],[Ar/N2O]and[Ar/SO2]molecular systems were recorded by the intra-pulse rapid-scan scheme.Finally,we have demonstrated that both experimental schemes are applicable for high resolution laser spectroscopy.The continuous wave segmented rapid-scan scheme works well even with a moderate vacuum pumping capacity and the intra-pulse rapid-scan scheme is capable to study unstable species such as radicals and ions.