Advanced

Studying the Dissociation Dynamics of Carbon Dioxide

Bulbucan, Claudiu LU (2017) MAXM30 20161
Department of Physics
MAX IV Laboratory
Abstract
Small molecules, and their fragmentation to smaller constituents upon excitation, are often used to understand how the bonds in a molecule are formed and how they break. One of such widely studied model molecule is CO2. This study aims at extending the knowledge of dissociation of carbon dioxide by measuring also the negatively charged fragments. In addition, these anions are linked to positive ions (cations) which are more abundant, and their production pathways are widely studied. The measurements were carried at Elettra Synchrotron Radiation Laboratory in Trieste, Italy. Provided that anion production at core-level excitation is far less abundant than that of electrons and cations, a new spectrometer was developed precisely for the... (More)
Small molecules, and their fragmentation to smaller constituents upon excitation, are often used to understand how the bonds in a molecule are formed and how they break. One of such widely studied model molecule is CO2. This study aims at extending the knowledge of dissociation of carbon dioxide by measuring also the negatively charged fragments. In addition, these anions are linked to positive ions (cations) which are more abundant, and their production pathways are widely studied. The measurements were carried at Elettra Synchrotron Radiation Laboratory in Trieste, Italy. Provided that anion production at core-level excitation is far less abundant than that of electrons and cations, a new spectrometer was developed precisely for the purpose of detecting the negative ions. It works in tandem with a positive ion spectrometer, mounted together for coincidence measurements. The properties and advantages of the present instrument, such as high acceptance angle and magnetic deflection of unwanted electrons are described. CO2 molecule is excited by photons which are energetic enough to promote core electrons of the oxygen atom to unoccupied molecular orbitals in CO2 - the following dissociation pathways are then studied by time-of-flight based mass spectroscopy. Both singly-charged and doubly-charged cations are found, in varying proportions, at different photon energies. Also, negative ions are seen, with C– being present only at the O1s edge but not at lower excitation energies. Furthermore, metastable states and triply-charged cations are a possibility, however, their complete analysis requires more attention. They are nonetheless discussed and analyzed to some extent. (Less)
Popular Abstract
Carbon dioxide is one of the most important chemical compounds to support life on Earth. It plays a crucial role in the process of photosynthesis through which plants naturally regulate the oxygen quantity from the atmosphere for aerobic beings, including humans.
The oxygen and carbon atoms which make the molecule are formed by electrons, protons and neutrons. The latter two form the atomic nuclei, having electrons "orbit" around them on circular-like paths called orbitals (this is not exactly true, but it is accurate enough for present explanations). When interacting with X-rays, electrons can "jump" on an energetically higher orbital or can even be completely ejected from the system, thus promoting the atom/molecule in an excited or... (More)
Carbon dioxide is one of the most important chemical compounds to support life on Earth. It plays a crucial role in the process of photosynthesis through which plants naturally regulate the oxygen quantity from the atmosphere for aerobic beings, including humans.
The oxygen and carbon atoms which make the molecule are formed by electrons, protons and neutrons. The latter two form the atomic nuclei, having electrons "orbit" around them on circular-like paths called orbitals (this is not exactly true, but it is accurate enough for present explanations). When interacting with X-rays, electrons can "jump" on an energetically higher orbital or can even be completely ejected from the system, thus promoting the atom/molecule in an excited or ionized state. Quantum mechanics states that the energy of the light must be precisely matched with the transition energy and for inner shell electrons these energies fall in the X-ray regime. If ionization is considered, the newly formed positively charged ion (with at least one electron missing) is unstable and, like all entities from nature, it tends to reach a state of equilibrium. One of the decay mechanisms is breaking into smaller fragments formed by its constituent atoms. Considering the fragments are not electrically neutral (this being the reason they are called ionic), in the presence of an electric field they will be accelerated in different directions (the difference arising from the sign of the charge + or -). Time of flight mass spectroscopy measures the time these fragments take from creation to detection, thus identifying them by coincidence measurements. This information is then used to determine the dissociation pathways of the studied molecule. This work describes the methods used in investigating the aforementioned properties, followed by conclusions and discussion regarding the interpretation of data. (Less)
Please use this url to cite or link to this publication:
author
Bulbucan, Claudiu LU
supervisor
organization
course
MAXM30 20161
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8929500
date added to LUP
2017-12-18 16:53:42
date last changed
2018-01-17 14:01:02
@misc{8929500,
  abstract     = {Small molecules, and their fragmentation to smaller constituents upon excitation, are often used to understand how the bonds in a molecule are formed and how they break. One of such widely studied model molecule is CO2. This study aims at extending the knowledge of dissociation of carbon dioxide by measuring also the negatively charged fragments. In addition, these anions are linked to positive ions (cations) which are more abundant, and their production pathways are widely studied. The measurements were carried at Elettra Synchrotron Radiation Laboratory in Trieste, Italy. Provided that anion production at core-level excitation is far less abundant than that of electrons and cations, a new spectrometer was developed precisely for the purpose of detecting the negative ions. It works in tandem with a positive ion spectrometer, mounted together for coincidence measurements. The properties and advantages of the present instrument, such as high acceptance angle and magnetic deflection of unwanted electrons are described. CO2 molecule is excited by photons which are energetic enough to promote core electrons of the oxygen atom to unoccupied molecular orbitals in CO2 - the following dissociation pathways are then studied by time-of-flight based mass spectroscopy. Both singly-charged and doubly-charged cations are found, in varying proportions, at different photon energies. Also, negative ions are seen, with C– being present only at the O1s edge but not at lower excitation energies. Furthermore, metastable states and triply-charged cations are a possibility, however, their complete analysis requires more attention. They are nonetheless discussed and analyzed to some extent.},
  author       = {Bulbucan, Claudiu},
  language     = {eng},
  note         = {Student Paper},
  title        = {Studying the Dissociation Dynamics of Carbon Dioxide},
  year         = {2017},
}