Restoration of rotating Fourier transform ultraviolet Raman spectrum with a time sequences trigger method

Rotating Fourier transform ultraviolet Raman spectrometer (RFTURS) is an ideal and valuable tool for atmospheric CO2 detection. However, due to the short excitation wavelength and the nonlinear relationship between the optical path difference (OPD) and the rotating angle, it is difficult for RFTURS to produce linear interference signals. This paper proposes a time sequences trigger (TST) method to realize linear sampling of interference signals. Specifically, time sequences are designed at equidistant OPD intervals as external clocking signals to trigger the data acquisition (DAQ) card to sample interference signals. High angular resolution and precise time sequences are obtained by using a gearbox to work at low speed as well as detecting the OPD zero via a sensor, respectively. By a simulation spectrum and white light, the method was tested and ultimately obtained the expected restored spectrum, which addresses the current drawbacks such as large error of the non-uniform fast Fourier transform (NUFFT) method and the subsampling method, and unsuitable work conditions of the reference laser method performing at the UV. This work provides significant guidance for field measurement of atmospheric CO2 by RFTURS.