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I first encountered Dan when he was “Dr. Kleppner” to me — when he taught one-third of Harvard’s three-sem<span style="-webkit-text-size-adjust: auto;">ester introductory physics sequence (he also was a member of Professor Norman Ramsey’s research group). It probably was the first formal course that Dan taught. He was a good lecturer; but what impressed me most strongly, then, was the sense of responsibility to students that he displayed when he lectured: he really *tried*.</span><div><br>I therefore looked forward to each presentation Dan (no longer “Dr. Kleppner”) gave to our Computer Group, and never was disappointed.</div><div><br></div><div> — Mike Alexander<br><div class="yahoo-signature"><br></div><br><p class="yahoo-quoted-begin" style="font-size: 15px; color: rgb(123, 106, 246); padding-top: 15px; margin-top: 0px;">On Monday, June 30, 2025, 12:21 PM, Ted Kochanski via LCTG <lctg@lists.toku.us> wrote:</p><blockquote class="iosymail"><div id="yiv3165671766"><div><div dir="ltr">All,<div><br clear="none"></div><div><br clear="none"></div><div>I met Dan when I was an MIT undergraduate -- long before I knew of the existence of the LCTG</div><div><br clear="none"></div><div>Dan also was sort of the Intellectual Grandfather to my brother Greg for his Ph.D. research "Magnetic Trapping and Cooling of Atomic Hydrogen" MIT 1987 </div><div><br clear="none"></div><div>Dan founded the lab and pioneered the cooling process that my brother used for his work with Spin Polarized Hydrogen</div><div>see for example:</div><div><br clear="none"></div><div>Magnetic Trapping of Spin-Polarized Atomic Hydrogen<br clear="none">Harald F. Hess, Greg P. Kochanski, John M. Doyle, Naoto Masuhara, Daniel Kleppner and Thomas J. Greytak<br clear="none">Copyright (c) 1987 The Japan Society of Applied Physics<br clear="none">Japanese Journal of Applied Physics, Volume 26, Number S3-1<br clear="none">Citation Harald F. Hess et al 1987 Jpn. J. Appl. Phys. 26 237<br clear="none">DOI 10.7567/JJAPS.26S3.237</div><div><br clear="none"></div><div>and</div><div><br clear="none"></div><div>Evaporative Cooling of Spin-Polarized Atomic Hydrogen<br clear="none">Naoto Masuhara, John M. Doyle, Jon C. Sandberg, Daniel Kleppner, Thomas J. Greytak, Harald F. Hess and Greg P. Kochanski<br clear="none">Publisher website<br clear="none">21 August 1988<br clear="none">Published by American Physical Society (APS) in Physical Review Letters<br clear="none">Vol. 61 (8) , 935-938<br clear="none"><a rel="nofollow noopener noreferrer" shape="rect" target="_blank" href="https://doi.org/10.1103/physrevlett.61.935">https://doi.org/10.1103/physrevlett.61.935</a></div><div><br clear="none"></div><div>and</div><div><br clear="none"></div><div>“Temperature and magnetic field dependence of three-body recombination in spin polarized hydrogen;” </div><div>H. F. Hess, D. A. Bell, G. P. Kochanski, D. A. Kleppner, T. J. Greytak, 1984 Phys. Rev. Lett. 52, 1520–1523</div><div><br clear="none">and</div><div><br clear="none">“Observation of three-body recombination in spin-polarized hydrogen;” H. F. Hess,<br clear="none">D. A. Bell, G. P. Kochanski, R. W. Cline, D. A. Kleppner, T. J. Greytak, 1983<br clear="none">Phys. Rev. Lett. 51, 483–486.<br clear="none"></div><div><br clear="none"></div><div>Ted</div></div><br clear="none"><div class="yiv3165671766gmail_quote yiv3165671766gmail_quote_container"><div id="yiv3165671766yqt07356" class="yiv3165671766yqt9002489748"><div dir="ltr" class="yiv3165671766gmail_attr">On Mon, Jun 30, 2025 at 8:41 AM Steve Isenberg via LCTG <<a rel="nofollow noopener noreferrer" shape="rect" ymailto="mailto:lctg@lists.toku.us" target="_blank" href="mailto:lctg@lists.toku.us">lctg@lists.toku.us</a>> wrote:<br clear="none"></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;" class="yiv3165671766gmail_quote"><div dir="ltr"><div style="font-family:sans-serif;font-size:small;color:rgb(11,83,148);" class="yiv3165671766gmail_default">Sad news. He will be missed.</div><br clear="none"><div class="yiv3165671766gmail_quote"><div dir="ltr" class="yiv3165671766gmail_attr">---------- Forwarded message ---------<br clear="none">From: <strong class="yiv3165671766gmail_sendername">Bea Kleppner</strong> <span><<a rel="nofollow noopener noreferrer" shape="rect" ymailto="mailto:bkleppner@gmail.com" target="_blank" href="mailto:bkleppner@gmail.com">bkleppner@gmail.com</a>></span><br clear="none">Date: Sun, Jun 29, 2025 at 11:42 PM<br clear="none">Subject: Dan Kleppner<br clear="none">To: Steve Isenberg <<a rel="nofollow noopener noreferrer" shape="rect" ymailto="mailto:smisenberg@gmail.com" target="_blank" href="mailto:smisenberg@gmail.com">smisenberg@gmail.com</a>><br clear="none"></div><br clear="none"><br clear="none"><div><div dir="ltr"></div></div><div><div dir="ltr"><br clear="none"><span style="font-size: 14.6667px;">Dear Steve,</span><div><span style="font-size: 14.6667px;">I am so sorry to write you the</span><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">sad news that my Dan unexpectedly died at Stanford hospital in California on June 16</span><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">Dan and I were in Palo Alto</span><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">to attend our grandson Darwin's high school graduation. </span><br clear="none" style="font-size:14.6667px;"><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">On Father's Day Dan enjoyed his favorite meal in Sofie's pretty garden.</span><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">His last words were a toast to honor Darwin and the young generation who, he said, will be doing exciting new things.</span><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">Then he collapsed. Despite CPR and ambulance to hospital, he did not regain consciousness.</span></div><div><span style="font-size: 14.6667px;">A link to his obituary in the Washington Post is below. A </span><span style="font-size: 14.6667px;">memorial will </span><span style="font-size: 14.6667px;">be held probably at MiT. I will let you know.</span></div><div><span style="font-size: 14.6667px;">There is solace in the long and happy life we had together and with his friends.He very much enjoyed his associattion with the Lexington computer and technology group. </span><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">He enjoyed life and was optimistic to the end.</span><br clear="none" style="font-size:14.6667px;"><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">Sadly,</span><br clear="none" style="font-size:14.6667px;"><span style="font-size: 14.6667px;">Beatrice Kleppner</span></div><div><span style="font-size:14.6667px;background-color:rgb(255,255,255);"><br clear="none"></span></div><div><span style="font-size:14.6667px;background-color:rgb(255,255,255);"><br clear="none" id="yiv3165671766m_1939816872368294636m_1172947083281014899lineBreakAtBeginningOfSignature"></span><div dir="ltr">Sent from my iPhone</div><div dir="ltr"><br clear="none"><blockquote type="cite"><br clear="none"></blockquote></div></div></div></div></div></div>
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