diff options
| -rw-r--r-- | abstract.tex | 2 | ||||
| -rw-r--r-- | dissertation.cls | 2 | ||||
| -rw-r--r-- | introduction/chapter.tex | 96 |
3 files changed, 68 insertions, 32 deletions
diff --git a/abstract.tex b/abstract.tex index fdaf7b9..8dd75a3 100644 --- a/abstract.tex +++ b/abstract.tex @@ -45,6 +45,6 @@ development work. % 1. processing software (\autoref{cha:pro}), 2. acquisition software (\autoref{cha:acq}) 3, active artifact correction (\autoref{cha:act}), 4. automated OPA calibration (\autoref{cha:opa}), and 5. finite pulse accountancy (\autoref{cha:mix}). % -Finally, \hyperref[prt:applications]{Part III: Applications} presents three examples where these +Finally, \hyperref[prt:applications]{Part III: Applications} presents four examples where these instruments, with these improvements, have been used to address chemical questions in semiconductor systems. %
\ No newline at end of file diff --git a/dissertation.cls b/dissertation.cls index d7fc4b2..e540902 100644 --- a/dissertation.cls +++ b/dissertation.cls @@ -190,6 +190,8 @@ anchorcolor=black]{hyperref} \RequirePackage[all]{hypcap} % helps hyperref work properly +\renewcommand{\chapterautorefname}{Chapter} + % --- bibliography -------------------------------------------------------------------------------- \RequirePackage[backend=biber, natbib=true, sorting=none, maxbibnames=99, isbn=false]{biblatex} diff --git a/introduction/chapter.tex b/introduction/chapter.tex index 18ffd06..fe43cb4 100644 --- a/introduction/chapter.tex +++ b/introduction/chapter.tex @@ -25,9 +25,9 @@ dimensionality and selection rules. % With the advent of ultrafast lasers, CMDS can resolve dynamics in excited states and the coupling
between them. \cite{RentzepisPM1970a} %
-CMDS is most often performed in the time domain, where multiple broadband pulses are scanned to
-collect a multidimensional interferogram. \cite{MukamelShaul2009a, GallagherSarahM1998a} %
-% BJT: scanned in WHAT? delay? time?
+CMDS is most often performed in the time domain, where multiple broadband pulses are scanned in
+time (phase) to collect a multidimensional interferogram. \cite{MukamelShaul2009a,
+ GallagherSarahM1998a} %
This technique is fast and robust---it has even been performed on a single shot.
\cite{HarelElad2010a} %
However time-domain CMDS has some fundamental limitations:
@@ -132,7 +132,6 @@ decreased acquisition times by up to two orders of magnitude. % Like any analytical technique, MR-CMDS is subject to artifacts: features of the data that are
caused by instrumental imperfections or limitations, and do not reflect the intrinsic material
response that is of interest. %
-% JCW: HOW THE EXPERIMENT WAS DONE, NOT WHAT IT IS HOPING TO MEASURE
For example, consider well-known artifacts such as absorptive effects \cite{CarlsonRogerJohn1989a},
pulse effects \cite{SpencerAustinP2015a}, and window contributions \cite{MurdochKiethM2000a}. %
Since MR-CMDS is a very active experiment, with many moving motors, an active approach to artifact
@@ -154,13 +153,13 @@ Resonant responses are impulsive, like a hammer hitting a bell. % The impulsive limit is particularly well suited for describing time domain experiments. %
In the driven limit, pulses are narrow in frequency and long in time compared to material
response. %
-Resonant responses are driven, like a jiggling jello dessert sitting on a washing machine. %
+Resonant responses are driven, like jiggling jello dessert sitting on a washing machine. %
The expected spectrum in both of these limits can be computed analytically. %
Things get more complicated in the mixed domain, where pulses have similar bandwidth as the
material response. %
Experiments in this domain are a practical necessity as CMDS addresses systems with very fast
-dephasing times. \cite{SmallwoodChristopherL2016a, PerlikVaclav2017a} % BJT: connect bw and
- % dephasing
+dephasing times. \cite{SmallwoodChristopherL2016a, PerlikVaclav2017a}
+% BJT: connect bw and dephasing
At the same time, the marginal resolution in frequency \emph{and} time that the mixed domain
possess promises huge potential in pathway resolution and decongestion.
\cite{PakoulevAndreiV2009a} %
@@ -170,34 +169,69 @@ An intuitive description of mixed-domain experiments is given. % False signatures of material correlation are discussed, and strategies for resolving true material
correlation are defined. %
-In \hyperref[prt:applications]{Part III: Applications}, three projects in which MR-CMDS was used to
+In \hyperref[prt:applications]{Part III: Applications}, four projects in which MR-CMDS was used to
answer chemical questions in materials systems are described. %
These chapters do not directly address improvements to the MR-CMDS methodology, but instead serve
as case studies in the potential of MR-CMDS and the utility of the improvements described in
\autoref{prt:development}. %
-[PARAGRAPH ABOUT PbSe QUANTUM DOTS]
-
-%Chapter \ref{cha:pbx} describes a series of experiments performed on PbSe quantum dots. %
-%Quantum dots are an excellent [STARTING SAMPLE... BEGINNING]
-%PbSe quantum dots are useful because [...] %
-%We learned [...] %
-
-[PARAGRAPH ABOUT MOS2]
-
-%Chapter [...] describes an experiment performed on MoS2.
-%MoS2 is useful because [...] %
-%We learned [...] %
-
-[PARAGRAPH ABOUT PEDOT:PSS]
-
-%Chapter [...] describes an experiment performed on PEDOT:PSS.
-%useful because...
-%we learned...
-
-% BJT: consider getting rid of the following paragraph
-% if it remains, it needs to address a more 'broader impacts approach' rather than simply
-% re-summarizing
+In \autoref{cha:pss}, we employ transient grating MR-CMDS to interrogate the photophysics of
+lead selenide (PbSe) quantum dots (QDs). %
+PbSe QDs are an interesting semiconductor system with many appealing properties for basic method
+development work. %
+They are easy to synthesize, store and prepare in the solution phase, and they have bright and
+relatively narrow band-edge excitons which are easy to interrogate using MR-CMDS. %
+In \autoref{cha:pss}, we describe a simple approach to extracting the quantitative third-order
+susceptibility of PbSe quantum dots using MR-CMDS. %
+Using a simple approach of standard dilutions, we define this susceptibility in ratio to the known
+well-quantified susceptibility of our solvent and cuvette windows. %
+A few-parameter model is employed to extract this ratio. %
+We are optimistic that this approach will be generally applicable, making it simple to perform
+quantitative solution-phase MR-CMDS. %
+
+In \autoref{cha:psg} we continue to investigate PbSe QDs. %
+Here we combine transient grating and transient absorption MR-CMDS to learn more about the
+nonlinear spectrum near the band edge, around the 1S exciton. %
+By combining both methods with the information from \autoref{cha:pss}, we are able to extract the
+complete amplitude and phase of the non-linear susceptibility. %
+We develop a simulation that relates the microscopic physics of PbSe electronic states to transient
+grating and transient absorption spectra, and fit our model to both spectra simultaneously. %
+Our model reveals the presence of continuum transitions, mostly invisible in typical transient
+absorption experiments. %
+We show that our model is able to describe spectra from two different syntheses with two different
+sizes of quantum dot. %
+
+In \autoref{cha:mx2} we report the first MR-CMDS study performed on a molybdenum disulfide thin
+film. %
+MoS\textsubscript{2} is a member of a class of materials called transition metal dichacolgenides
+which have recently attracted a large amount of attention for their unique photophysical
+properties. %
+These thin films have relatively low optical density and are highly scattering, making them
+particularly challenging for MR-CMDS experiments. %
+We employed several strategies to overcome these challenges, and performed three dimensional
+frequency-frequency-delay transient grating spectroscopy to understand the basic coupling and
+dynamics of MoS\textsubscript{2}. %
+We show that the band-edge excitons of MoS\textsubscript{2} are not easily resolved, and the
+dynamics of MoS\textsubscript{2} are fast. %
+We develop a picture of MoS\textsubscript{2} electronic states that is consistent with our
+results. %
+
+In \autoref{cha:pps} we use MR-CMDS to interrogate the dynamics of electronic states of
+(PEDOT:PSS). %
+PEDOT:PSS is a transparent, electrically conductive polymer. %
+The exact origin of the conductivity is not well understood, so it is unclear how to improve the
+conductivity or synthesize other conductive polymers. %
+We performed photon echo experiments on PEDOT:PSS, directly interrogating the electronic states
+that are responsible for conductivity in the polymer. %
+Using a sophisticated model extended from the work in \autoref{cha:mix}, we constrain the pure and
+ensemble dephasing lifetimes of PEDOT:PSS. %
+These lifetimes can be directly related to the homogeneous and inhomogeneous broadening parameters
+in PEDOT:PSS. %
+Amazingly, we find that PEDOT:PSS has very broad homogeneous \emph{and} inhomogeneous
+linewidths. %
+We cannot constrain either quantity, but we can put lower limits on both. %
+This basic information is complementary to other experiments in the ongoing effort to fully
+understand PEDOT:PSS. %
Despite challenges in software, hardware, and theory MR-CMDS is a crucial tool in the hands of
scientists. %
@@ -206,4 +240,4 @@ hardware development. % PyCMDS has enabled new experiments, and has made data collection faster and more artifact-free. %
WrightTools has trivialized data processing, tightening the loop between idea and execution. %
Theory can be used to guide experimental insight in the promising, if challenging, mixed domain. %
-Applications of these ideas in three materials are presented. %
+Applications of these ideas in three material systems are presented. %
|