High Resolution Far Infrared Laser Spectroscopy Of Simple Stable And Unstable Molecules

Far infrared laser spectroscopy of simple stable and unstable molecules plays an important role in astrophysics, atmospheric chemistry and chemical reaction dynamics. Firstly, this dissertation focused on two techniques of far infrared laser spectroscopy: FIR-LMR and TuFIR spectroscopy. Secondly, characteristic and analyzing method of far-infrared laser magnetic resonance spectra of halogen-containing radicals were investigated. Finally, the pure rotational spectra of CHF₃, as well as pressure broadening on SO₂ were studied.Fluoroform is one of the most significant stable molecules of greenhouse gas in atmospheric physics. The Global Warming Potential of this molecule has risen to prominence. It has been of great interest to physicists and chemists. Using Tunable Far Infrared Laser (TuFIR) spectrometer by collaboration with Cambridge University, the high resolution rotational spectra of CHF₃ were successfully measured and assigned including the splitting of the K=3 transitions. The least-squares fit of our spectra together with published data of microwave and far infrared spectra gives more precise rotational spectra parameters than before.Sulfur dioxide, as one of 37 important atmospheric molecules monitered by HITRAN, has been a significant object of spectroscopic study for a long time. The measurement of pressure broadening coefficient of SO₂ in laboratory can provide necessary data for concentration monitor in interstellar and Earth's atmosphere. With accurate calibration and test for laser intensity and pressure gauges of TuFIR spectrometer, nitrogen and self-broaden ing coefficients of SO₂ have been measured firstly for rotational transitions of 702.29336(38_2.36-37_3.35) and 694.49401 (39_1.39-38_0.38) GHz lines. As compared with other study, this measurement is an order more precise. Our work not only supports ATC theory that Ka dependence for the broadenings of B-type transition is significant, but also reveals the disadvantages of the theory.