Abstract
Simple amines are basic model system of nitrogen-containing chromophores that appear
widely in nature. They are also ideal systems for detailed investigation of nonadiabatic
dynamical processes and ultrafast temporal evolution of electronic states of
the Rydberg type. This investigation, combining experiments with calculations, provides
new insight into the nature of the internal conversion processes that mediate the
dynamical evolution between Rydberg states, and how structural variations in simple
amine system have a large impact on the non-adiabatic processes.
The experimental method of choice is femtosecond time-resolved photoelectron velocity
map imaging (VMI), which is a newtechnique in the Copenhagen lab. The design,
building and implementation of the VMI spectrometer has been a very substantial part
of the thesis work. This techniques oers enhanced information content in the form
of ecient and sensitive collection of photoelectron spectra. In particular, the angleresolved
data available from the VMI approach provides highly detailed mechanistic
insight about the relaxation pathways.
One striking novel nding is that for tertiary amines, the critical factor driving
the non-adiabatic dynamics is the evolution of a Rydberg 3p state into valence character
along an N-C stretching coordinate. The exact geometric structure of the tertiary
amines have been found to inuence the relaxation process through conformational rearrangement,
and the eects of symmetry and rigidity have been investigated through
a cage structure. The VMI technique has been found to be very useful in investigating
the nature of the coupling between the states and provides hints to the fate of the 3s
state which has previously been a mystery.
This is in prominent contrast to the primary and secondary amines as well as previously
investigated organic species containing N-H bonds, where the ultrafast evolution
of the 3s state into valence character iswell-established. Even though the temporal evolution
is too fast to be resolved by the experiment, the angle-resolved information still
allows for the observation of this process in a spectrally averaged way
widely in nature. They are also ideal systems for detailed investigation of nonadiabatic
dynamical processes and ultrafast temporal evolution of electronic states of
the Rydberg type. This investigation, combining experiments with calculations, provides
new insight into the nature of the internal conversion processes that mediate the
dynamical evolution between Rydberg states, and how structural variations in simple
amine system have a large impact on the non-adiabatic processes.
The experimental method of choice is femtosecond time-resolved photoelectron velocity
map imaging (VMI), which is a newtechnique in the Copenhagen lab. The design,
building and implementation of the VMI spectrometer has been a very substantial part
of the thesis work. This techniques oers enhanced information content in the form
of ecient and sensitive collection of photoelectron spectra. In particular, the angleresolved
data available from the VMI approach provides highly detailed mechanistic
insight about the relaxation pathways.
One striking novel nding is that for tertiary amines, the critical factor driving
the non-adiabatic dynamics is the evolution of a Rydberg 3p state into valence character
along an N-C stretching coordinate. The exact geometric structure of the tertiary
amines have been found to inuence the relaxation process through conformational rearrangement,
and the eects of symmetry and rigidity have been investigated through
a cage structure. The VMI technique has been found to be very useful in investigating
the nature of the coupling between the states and provides hints to the fate of the 3s
state which has previously been a mystery.
This is in prominent contrast to the primary and secondary amines as well as previously
investigated organic species containing N-H bonds, where the ultrafast evolution
of the 3s state into valence character iswell-established. Even though the temporal evolution
is too fast to be resolved by the experiment, the angle-resolved information still
allows for the observation of this process in a spectrally averaged way
| Originalsprog | Engelsk |
|---|
| Forlag | Department of Chemistry, Faculty of Science, University of Copenhagen |
|---|---|
| Antal sider | 226 |
| Status | Udgivet - 2015 |