<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns:mv="http://macVmlSchemaUri" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Title" content="">
<meta name="Keywords" content="">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal;
font-family:"Calibri",sans-serif;
color:windowtext;}
span.EmailStyle18
{mso-style-type:personal;
font-family:"Calibri",sans-serif;
color:windowtext;}
span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
span.msoIns
{mso-style-type:export-only;
mso-style-name:"";
text-decoration:underline;
color:teal;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style>
</head>
<body bgcolor="white" lang="EN-US" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal"><span style="font-size:14.0pt">There will be a Modern Optics and Spectroscopy Seminar held next
<b>Tuesday, February 13 at 12pm </b>in 34-401:</span><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:14.0pt"> </span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:14.0pt">Leora Dresselhaus-Cooper</span></b><o:p></o:p></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">Massachusetts Institute of Technology</span></i><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:14.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><b><i><span style="font-size:16.0pt">Imaging Shock Waves to Study Initiation in Molecular Explosives<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:14.0pt"> </span></i></b><o:p></o:p></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">Shock waves push materials far from equilibrium, causing transformations that permanently alter the system. Characterizing the exotic phase transformations or fracture is difficult, as shock waves interact
strongly with initial material defects, causing the irreversible dynamics to fluctuate significantly between samples. To understand how shock waves induce material changes, we must measure the response in-situ, measuring all of the relevant sub-nanosecond
information in a single acquisition. Furthermore, the techniques must give signals that are interpretable over the large variation in pressure and temperature found in shock waves. These challenges cause much of our understanding of shocked materials to follow
experimental technique development.<o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span style="font-size:14.0pt">Using a novel tabletop optical method, I study 150-μm diameter cylindrically converging shock waves in a quasi-2D sample. I present a novel imaging diagnostic that captures a sequence of ultrafast images
in a single acquisition. With this new imaging tool, I show how the nonlinearities in shock waves form a coupled-wave structure when propagating parallel to an interface, as seen in our acoustic waveguide geometry. Using this and other diagnostics, I then
investigate how shock waves initiate explosive chemistry in 1,3,5-triaza-1,3,5-trinitrocyclohexane (RDX). While RDX has been used for industrial and weapons applications for decades, much is still unknown about the molecular mechanism by which shock waves
initiate large-scale detonations. My experimental findings on single crystals of RDX in-situ and after recovery show phase transitions, fracture, deflagration and voids that give significant insight into how shock waves initiate the underlying chemistry.<o:p></o:p></span></i></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <br>
<br>
</span><o:p></o:p></p>
<p class="MsoNormal">Refreshments will be served immediately following the seminar<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt">Christine Brooks</span></b><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Administrative Assistant</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Massachusetts Institute of Technology</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Department of Chemistry</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">77 Massachusetts Ave, 6-333</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Cambridge, MA 02139</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">p: 617.253.7239</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">e: <a href="mailto:cbrooks@mit.edu">cbrooks@mit.edu</a></span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</body>
</html>