Microwave spectroscopy allows study of the bond lengths and angles of molecules and molecular complexes. Gas phase molecules are exposed to microwave radiation while entrained within a molecular beam. The observed microwave spectrum can be used to calculate the physical dimensions of the molecules being excited. This thesis primarily discusses the building and modification of a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer and its use in conjunction with an established Balle-Flygare Fourier transform microwave (BF-FTMW) spectrometer in order to efficiently record and assign spectra. The CP-FTMW spectrometer was built and extensively used to observe spectra in the 6.5-19 GHz range. It is possible to measure a spectrum in one day using this spectrometer when it would require many weeks of manual measurements on the BF-FTMW spectrometer to do so. This thesis will explore weakly-bound complexes involving two subunits, the first being a Lewis base such as ethene, ethyne, ammonia or carbon monoxide, and the second an electron acceptor such as the iodine in CF3I, or the metal in the metal halides, AgCl or CuCl. These weakly bound molecular complexes present an opportunity to examine the fundamental interactions between the electron donor of the Lewis base molecules and the electron acceptor of the partner molecule. Five molecular complexes in their ground rotational state consisting of CF3I bonding to various Lewis bases have been investigated. These weakly bound complexes in the form CF3I ·· . B have the structure of a C3v molecule. Under this treatment CF3I··· Kr, CF3I··· CO, CF3I··· NH3, CF3I···N(CH3)3 and CF3I···PH3 have been found to have quartic force constants, kδ of between 3 and 12 Nm-1. The complexes CF3I···NH3, CF3I···N(CH3)3 and CF3I··· PH3 have been found to display evidence for internal rotation of the smaller Lewis base subunits with respect to the heavier CF3I subunit on the C3 axis of symmetry. These are assigned as A and E states, to which the internal rotation quantum number m transitions correspond to m = 0 and m = ±1 respectively. Several complexes in the form C2Hn···M - Cl where n = 2 or 4 and M = Cu or Ag. These molecules are found to have planar C2v symmetry.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:684746 |
| Date | January 2014 |
| Creators | Stephens, Susanna Louise |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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