Molecular Saturated Absorption Based on Cavity Ring-down Spectroscopy

Author:Tao Lei Gang

Supervisor:hu shui ming


Degree Year:2018





Laser spectroscopy is one of the most important method to study the structure and dynamics of atoms and molecules.Precise spectral data of molecules can be not only ap-plied as frequency references in a wide spectral range,but also used to test fundamental physics and constants,and even in search of physics beyond the Standard Model.The thesis focuses on the development of laser-cavity-comb locked cavity ring down spec-troscopy(CRDS)apparatus,and its application in saturated absorption spectroscopy of overtone ro-vibrational transitions of molecules to determine their frequencies with unprecedented accuracy.The main content of this thesis is as follows:The first chapter briefly introduces the background of precision spectroscopy of molecules and the methodology including widely used saturation spectroscopy.The principles of CRDS and its application in saturation spectroscopy is also presented.Chapter Ⅱ introduces CRDS based on cavity-swept matching to the laser frequency,including its configuration,optical layout,and the frequency calibration.A changing cavity length introduces Doppler shift.The effect was investigated from the Lamb dips of acetylene transitions through the analysis of the line profile,width and center.Chapter Ⅲ presents the laser-cavity-comb locked CRDS.The saturation spec-troscopy of 45 lines in the v1 + 3v3 band of acetylene were studied and the line centers were determined with a fractional accuracy of 8 × 10-12.Comparison with previous studies was also presented.In Chapter IV,we first give a review of the study on the spectroscopy of molecular hydrogen in its electronic ground state.We also explain the potential to determine the proton-electron mass ratio from the ro-vibrational spectroscopy of the molecular hydro-gen.The R(1)line in the v2 band of HD near 1.4 μm was studied.Both Doppler-limited and saturation spectra of this line were recorded.The transition frequency was deter-mined with a fractional accuracy of 4 × 10-10.The result from this work was compared with theoretical calculations and other experimental results.