Design of a molecular beam apparatus to generate mass selected ion clusters: Infrared absorption of fluoroform in cryogenic solutions

Low temperature techniques are very useful in the interpretation of molecular spectra. Spectroscopy in molecular beams and in cryogenic solutions have been proved to be very efficient methods to reduce the congestion found in the spectra of molecules at room temperature. First, the design of a molecular beam apparatus to generate mass selected ion clusters is presented. A description of the vacuum system, ionization sources and mass selection and detection stages is given. An electrospray ion source was built. Operational parameters were optimized based on current measurements of the electrospray current before and after the expansion into the beam apparatus. Coupling of the source to the mass selection and time of flight mass spectrometer detector is discussed. Glow discharge ionization sources are described. The effect of different experimental parameters on the cluster distributions and intensities is studied, as well as the reproducibility of ion signals. A discussion on the mass selection of ions generated with the discharge using a velocity filter is presented. Instrument control and data acquisition and analysis using LabVIEW RTM software is described. Software was developed to acquire laser photodissociation spectra.; The second part presents the study on the solvent effects on the infrared absorption (400--4000 cm-1) frequencies and bandwidths of fluoroform in diluted cryogenic solutions of argon and nitrogen at 95 K, and xenon at 170 K. Frequency shifts have been compared to those calculated by ab initio methods at the HF/631G level. An analysis of the dynamics of the relaxation has been done based on the analysis of the infrared spectra. Time correlation functions were obtained for the nu1, nu 3, and nu4 vibrational modes. A discussion of the results is given based on the temperature dependence of the bandwidths and band moments in liquid argon. A hydrodynamic model is applied to explain the differences in the relaxation process in the three solvents.