HIGH-RESOLUTION FOURIER TRANSFORM INFRARED (FTIR) SPECTROSCOPY FOR SOME GASEOUS ASYMMETRIC TOP MOLECULES

Abstract

A series of investigations in the vibrational-rotational structure have been made for the gaseous asymmetric top molecules of nitric acid (H14NO3 and H15NO3), isotopically substituted water (HD180 and D218O), 1,1-difluoroethylene (CF2=CH2), and bromochloromethane (CH2BrCl). The mid-infrared spectra have been measured at high resolutions from 0.0014 cm-1 to 0.008 cm-1 with the Bomem DA3.002 and the modified DAS Fourier transform spectrometers. The rotationally resolved spectra were interpreted, assigned and simulated using the technique of least-squares fit. The present thesis consists of thirteen chapters. Chapters 1 to 5 are devoted to the introduction of some fundamental background knowledge, including a brief review of FTIR spectroscopy, a schematic description of our Bomem DA3.002 Fourier transform spectrometer, a concise elucidation of Watson's reduced rotational Hamiltonian and the nonlinear least-squares fit algorithm. Chapters 6 to 12 focus on the detailed measurements and analyses of tlw high-resolution infrared spectra of the v8+v9/v6+v7, v6, v7, v8 bands of H12NO3, the v2 band of H15NO3, the v2 bands of HD18O and D218O, the v2/v8+v10 bands of CF2=CH2, and the v1 band of CH2BrCl. Line intensities and positions were investigated and accounted for the v8 band of HN03, and appropriate operator coefficients of the transition dipole moment were determined from the simulation of a number of individual line intensities. For the other bands, line-position simulation was the subject of the studies and consequently, accurate rovibrational constants were obtained. For the coupled hands, i.e., v8+v9/v6+v7 of HN03 and v2/v8+v10 of CF2=CH2, rovibrational interacting terms were necessarily introduced in the Watson's Hamiltonian so that accurate reproduction for the perturbed lines was achieved. Concluding remarks and a summary of the results from the present work rn·e given in chapter 13. Further work of considerable significance, in the field of high-resolution molecular spectroscopy is also proposed in this last chapter.