Time-resolved Fourier transform infrared spectroscopy: Application to pulsed discharges

Time-resolved Fourier transform spectroscopy (TR-FTS) is reviewed, with emphasis on synchronous FTS using continuously scanning interferometers. By using a high-resolution Bruker IFS 120 HR, a TR-FTS method has been developed with the help of a microcontroller SX, where a maximum of 64 time-resolved data are recorded with a preset time interval in a single scan of the interferometer. The time resolution is 1 μs, limited by the response time of the detector system used. This method has been applied to a pulsed discharge in an Ar and H2 mixture to observe time profiles of ArH+ and ArH emission spectra. Electronic transitions of He2 have been observed in the infrared region with this method, and from the time profiles, He2 in Rydberg states with higher energy than the b3Π state is found to be produced efficiently in afterglow plasma. Fifteen bands in the 2300-8000 cm−1 region have been assigned by using previously reported data from the optical region. A new band from the 5f state has been assigned for the first time through the 5f-4d band in the 2600 cm−1 region.