High-resolution Cryogenic Matrix Isolation Spectroscopy For Carbon Dioxide And Other Molecules

Since the molecular spectroscopy was known in the early years, it has alwaysbeen an important subject for people. Nowadays it developes quickly with the rapidinprovement of the science and techniques. As it helps people to know the struc-ture and the property of various of molecules from both microscale and macroscale,it plays an important role in photochemistry, astrophysics and environmental appli-cations. Many of those studies concerns people's daily life, especially the study ofthe atmospheric moleclues. While more and more deep secrets of those atmosphericmolecules were revealed, one could know more details of the processes of the green-house effect, and the effects to the ozonosphere from atmospheric molecules underthe sun, also the influences of the increasing pollution. With the development of ex-periment technique, people can simulate spectroscopy in astrophysical environment–cryogenic matrix isolation spectroscopy, which could be used to study interactions ordynamics between molecules. The content of this thesis is about the spectroscopy ofsome simple molecules,which contains mainly two parts: one is the analysis of¹⁵N₂¹⁶Ospectra,which could be used to improve the Hitran database; the other is the computersimulation of interactions of some simple molecules, which concern the matrix isola-tion experiments in our laboratory.In chapter 1 the principle of the infrared spectroscopy of simple linear moleculesis introduced, which is the theoretical basis of the work introduced in chapter 2.Thematrix isolation spectroscopic technique is also roughly introduced, which concernsthe work in chapter 3 and chapter 4.In chapter 2 we observes and analyzes the FTS spectra of15N216O in the range of1650～3450 cm 1.73 bands and 7743 transitions are assigned and used to fit the spec-tral parameters.However,compared to its three isotopic molecules,¹⁵N₂¹⁶O,¹⁵N¹⁴N¹⁶Oand¹⁴N¹⁵N¹⁶O, the deviations between the predicted and the observed values of¹⁵N₂¹⁶Oare larger, for example, the position deviations are in the range of -0.65～0.7 cm1.So,someimportant parameters of the current effective Hamiltonian model of¹⁵N₂¹⁶O are stillnot discovered and more experimental data are required.In chapter 3 we first introduce the theoretical method Ran et al used to study the CO₂-H2interactions.Then we introduce the potential energy surface of CO₂moleculeamong 12 H2molecules(hcp or fcc lattice).The potential energy surface we constructwill be helpful in the discussion of chapter 4. Besides,for interaction between H2O andCH3OH, we analyze the vibration modes and the vibration frequencies. The resultsare compared with the cryogenic matrix isolation spectral experiments and get goodconsistency.In chapter 4 we recorded the spectra of CO₂in cryogenic para-hydrogen matrixand abundant spectral lines in theν3wave band are observed. A series of experimentalmethods, such as isotopic molecule experiments,annealing procedure and changing theconcentration of CO₂or O₂etc.,and theoretical simulation are carried out to find thegeneration mechanism of the lines. Our conclusion is that the band splitting is mainlydue to tunneling effect which is caused by"cage effect",and the much subtler spectralstructure is due to the number of nearest orth-hydrogen,which could be assigned as1,2,3...