From 0f87beb9b3cbf8447f4850be0eb9874e9c4fb64f Mon Sep 17 00:00:00 2001 From: Blaise Thompson Date: Sun, 15 Apr 2018 16:11:28 -0500 Subject: 2018-04-15 16:11 --- introduction/chapter.tex | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) (limited to 'introduction') diff --git a/introduction/chapter.tex b/introduction/chapter.tex index f6adc46..b3d9df5 100644 --- a/introduction/chapter.tex +++ b/introduction/chapter.tex @@ -16,10 +16,10 @@ Coherent multidimensional spectroscopy (CMDS) is a family of experimental strategies capable of providing unique insights into microscopic material physics. % -It is similar to more familiar multidimensional NMR experiments \cite{ZhaoWei2000b, - PakoulevAndreiV2006a}, although the implementation is different due to differences between the -behavior of nuclear spin states (probed by NMR) and electronic and vibrational states (probed by -CMDS). % +It is similar to more familiar multidimensional NMR experiments \cite{KeustersDorine1999a, + ZhaoWei2000b, PakoulevAndreiV2006a}, although the implementation is different due to differences +between the behavior of nuclear spin states (probed by NMR) and electronic and vibrational states +(probed by CMDS). % CMDS can resolve couplings between states, and can decongest spectra by taking advantage of dimensionality and selection rules. % With the advent of ultrafast lasers, CMDS can resolve dynamics in excited states and the coupling @@ -146,6 +146,16 @@ complementary to chopping. % Automated poynting correction and power correction can account for non-idealities in OPA performance. % +MR-CMDS instruments rely on OPAs as tunable light sources. % +OPAs are very sensitive to changes in upstream lasers and lab conditions, so OPA tuning is +regularly required. % +Manual OPA tuning can easily take a full day of human effort. % +Furthermore, manual tuning typically results in inferior tuning curves, since it is difficult for +humans to consider all available information simultaneously. % +Automated OPA tuning makes OPA upkeep easier, faster and more reproducible, facilitating higher +throughput, higher quality frequency domain experiments. % +Chapter \ref{cha:opa} describes fully automated tuning algorithms which I have developed. % + The theory that is used to describe CMDS is typically derived in one of two limits. % In the impulsive limit, pulses are broad in frequency and short in time compared to material resonances. % @@ -183,8 +193,8 @@ They are easy to synthesize, store and prepare in the solution phase, and they h 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. % +Using 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. % @@ -213,23 +223,23 @@ frequency-frequency-delay transient grating spectroscopy to understand the basic 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 +We describe 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. % 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. % +that are speculated to participate in conductivity. % 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. % +We cannot fully determine 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. % -- cgit v1.2.3