From c561cd27239ede72090bfd8f8cc785c52ae48673 Mon Sep 17 00:00:00 2001
From: Blaise Thompson <blaise@untzag.com>
Date: Fri, 13 Apr 2018 18:16:17 -0500
Subject: 2018-04-13 18:16

---
 introduction/chapter.tex | 96 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 65 insertions(+), 31 deletions(-)

(limited to 'introduction/chapter.tex')

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.  %
-- 
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