Brown, Michael
(2018)
The Study of Positive-Ion Mass Spectrometry of
5-Fluorouracil Using Low-Energy Electron
Impact.
Masters thesis, National University of Ireland Maynooth.
Abstract
The aim of the experiment described within this thesis was to generate a molecular beam
of 5-fluorouracil and to investigate the fragmentation processes that were induced by
low-energy electron impact. The apparatus is contained in a vacuum chamber with three
main compartments: the expansion chamber, the collision chamber and the flight-tube.
The expansion chamber is where the molecular beam is produced by a resistively heated
oven containing 5-fluorouracil powder. The molecular beam enters the collision chamber
through a skimmer where it is crossed with a pulsed electron beam. The electron beam has
a pulse width of 0.5 ms providing good time-of-flight resolution. Positive ions produced
by electron collisions with the molecules are extracted into a reflectron time-of-flight
mass spectrometer. The field-free region and the reflector of the time-of-flight mass
spectrometer are both located in the flight-tube. The reflector is positioned at the end of
the flight-tube and directs the ions back into the field-free region towards the detector. A
multichannel scaler triggered synchronously with the electron pulse is used to accumulate
time-of-flight spectra.
Using computer-controlled data acquisition, mass spectra were measured for electron
impact energies from 5 eV - 100 eV in 0.25 eV steps. Ion yield curves for most fragment
ions were determined by fitting groups of peaks in the mass spectra with sequences of
normalised Gaussians. The appearance energies for these ions were determined by fitting
onset functions to the ion yield curves. By comparing the mass spectra and the appearance
energies with those of uracil, new information about fragmentation processes is obtained.
| Item Type: |
Thesis
(Masters)
|
| Keywords: |
Study; Positive-Ion Mass Spectrometry;
5-Fluorouracil; Low-Energy Electron
Impact; |
| Academic Unit: |
Faculty of Science and Engineering > Experimental Physics |
| Item ID: |
9905 |
| Depositing User: |
IR eTheses
|
| Date Deposited: |
11 Sep 2018 14:19 |
| URI: |
|
| Use Licence: |
This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available
here |
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