Winter 2018 | jila.colorado.edu p.1 JILA Light & Matter Some “Crazy Hat Day” participants at JILA on January 25, 2018. Credit: Catherine Klauss, JILA. JILA Light & Matter is published quarterly by the Scientific Communications Office at JILA, a joint in- stitute of the University of Colorado Boulder and the National Institute of Standards and Technology. The science communicators do their best to track down recently published journal articles and great research photos and graphics. If you have an image or a recent paper that you’d like to see featured, contact us at: [email protected]. Please check out this issue of JILA Light & Matter online at https://jila.colorado.edu/publications/jila/ light-matter. Kristin Conrad, Project Manager, Design & Production Catherine Klauss & Julie Phillips, Science Communicators Steven Burrows, Art & Photography Gwen Dickinson, Editor Winter 2018 | jila.colorado.edu Stories It’s Triplets! 1 Something New Under the Sun 3 Molecule Movies, Now Filming at NIST 5 A New Quantum Drum Refrain 7 And, The Answer Is...Still Round 19 E.T. Phone Home 21 The Clock That Changed the World 23 Features Feature: Molecular Spectroscopy at JILA 9 In the News 16 Atomic & Molecular Physics Newly minted JILA Ph.D. Catherine Klauss and her atom sample, which was expected for a two-atom 85 colleagues in the Jin and Cornell group decided molecule, or dimer ( Rb2). to see what would happen to a Bose-Einstein con- densate of Rubidium-85 (85Rb) atoms if they sud- But the initial decay was happening much too fast denly threw the whole experiment wildly out of to involve dimers. After consulting with JILA theo- equilibrium by quickly lowering the magnetic field rist José D’Incao, Klauss and her colleagues con- through a Feshbach resonance1. Theoretically, this cluded they were making three-atom molecules, maneuver is predicted to make the atoms infinitely or trimers. And, the trimers were almost certain- 85 attracted to each other, and at the same time, infi- ly the Efimov molecules ( Rb3) that have been nitely repulsed by each other. studied theoretically for nearly 50 years, including work by D’Incao over the “This is a really crazy regime, “This is a really crazy regime, past decade. In this ex- and things happened really and things happened really periment, about 8% of the fast,” explained Klauss. “At fast,” explained Klauss. “At ultracold 85Rb atoms in the this resonance, the energy of original BEC formed the the atom pairs equaled the this resonance, the energy of exotic Efimov molecules. energy of molecules, and the the atom pairs equaled the interactions were going on energy of molecules, and the “This is the first direct ob- like crazy.” interactions were going on like servation of Efimov mol- ecules in an ultracold gas At first, Klauss and her col- crazy.” that we’ve already positive- leagues thought they were ly identified,” Klauss said. losing most of the atoms in the experiment. “You can tell these molecules apart from dimers However, they soon discovered the atoms were because the Efimov trimers die faster. José’s theory actually still there even though the research- predicted that Efimov trimers would have a life- ers couldn’t see them any longer. The atoms had time of about 100 microseconds (10-4 s), and that’s been transformed into molecules, which had to be exactly what we see in the lab!” probed differently. The researchers responsible for discovering and in- Once the researchers realized they’d made mol- vestigating the 85Rb triplets included Klauss, gradu- ecules, they decided to study them. First, they ate student Xin Xie, University of Colorado Boulder held the molecules at a specific magnetic field and undergraduate student Carlos Lopez-Abadia, senior watched them decay away by turning back into research associate José D’Incao, Fellows Deborah atoms. But, no matter how many times they repeat- Jin and Eric Cornell as well as Zoran Hadzibabic of ed the experiment, there was always a two-com- the University of Cambridge. ✺ ponent decay: a fast one and a slower one. The slower decay varied with the density of the initial Catherine E. Klauss, Xin Xie, Carlos Lopez-Abadia, José P. D’Incao, Zoran Hadzibabic, Deborah S. Jin, and Eric A. Cornell, Physical Review Letters 1. Near a Feshbach resonance, small changes in the magnetic field have 119, 143401 (2017). dramatic effects on the interactions of atoms in an ultracold gas. 1 Winter 2018 , JILA Light & Matter By quickly lowering the magnetic field in a Bose-Einstein condensate, Catherine Klauss and her colleagues in the Jin-Cornell group made a lot of two-atom molecules of rubidium 85 ( Rb2). They also directly observed and identified—for the first time ever in an ultracold gas—about 8% of their molecules as Efimov molecules made of three rubidium atoms 85 ( Rb3). Credit: The Jin and Cornell group and Steve Burrows, JILA Winter 2018 . JILA Light & Matter 2 Astrophysics Figure (left): Sunspot on the surface of the Sun surrounded by megameter-sized granules. Credit: Big Bear Solar Observatory Figure (right): Solar Dynamics Observatory photograph of the Sun’s corona. Deep inside the Sun, hurricane- like swirling columns generate megameter-sized granules and 30 megameter-sized supergranules that appear under the corona on the Sun’s surface. Credit: sdo.gsfc.nasa.gov Something New Under the Sun 3 Winter 2018 , JILA Light & Matter Astrophysics The Sun isn’t working the way we thought it did. of observational data that has never detected a Many astrophysicists haven’t actually understood single giant cell to mean that they aren’t there.” one aspect of how the Sun worked—until former senior research associate Nick Featherstone and Hindman and Featherstone used some fancy math senior research associate Brad Hindman set the and numerical simulations that included rotation record straight. and coriolis forces to see what might actually be generating supergranules on the surface of the Stars like the Sun have to get rid of the heat gener- Sun. Much to their surprise, they discovered mul- ated by thermonuclear reactions in their centers. tiple column-like structures not unlike spinning The Sun’s secret is vigorous hurricanes on Earth. convection, particularly in Thus it seems, the Sun the outer third of the Sun “There is nothing like this closest to its surface. Like a has two distinct layers on the surface of the Sun,” pot of boiling water, hot fluid Hindman explained. “Instead moves upward and cooler of convection: (1) a they exist below the surface fluid moves downward, car- deep layer where little in the top third of the Sun, but rying heat outwards toward why?” the surface of the star. For spinning columns form, a long time, astrophysicists The answer is simple. Deep thought these motions came and (2) a layer near the layers of the Sun have fluid in two different sizes called surface where flows are motions with the same time granules (because these scale as the Sun’s period of ro- megameter-sized structures too fast to form columns, tation. These deep-layer struc- looked like grains of rice tures are prone to spin, unlike through early telescopes) so they form granules what happens near the surface and giant cells. and supergranules. where lateral flows are much faster. And, the columns must The trouble with the giant be smaller than 30 megame- cell idea is that while granules appear on the ters in radius, or telescopes would have detected Sun’s surface, giant cells have never been seen in them long before now. spite of the fact astronomers have been looking for them for a long time. And, if giant cells exist, Thus, it seems, the Sun has two distinct layers of they would be 200 megameters1 wide, which is convection: (1) a deep layer where little spinning definitely large enough to be detectable. For in- columns form, and (2) a layer near the surface stance, the largest cells seen in the Sun, called su- where flows are too fast to form columns, so they pergranules, are only about 30 megameters wide. form granules and supergranules. Featherstone’s and Hindman’s new theory explains why supergranulation appears and why giant cells The conclusion is clear: The Sun has no giant cells, are absent. which is why no one has ever seen them.✺ “I’ve been thinking about this problem for about Nicholas A. Featherstone and Bradley W. Hindman, The Astrophysical 10 years,” Hindman said. “About two to three years Journal Letters830 , L15 (2016). ago, I decided we should accept the huge volume 1. A megameter is 1000 kilometers, and one mile is about 1.6 kilometers. Winter 2018 . JILA Light & Matter 4 Biophysics Molecule Movies, Now Filming at NIST The actors are mole- cules. The plot, broken molecular bonds. JILA Fellow Ralph Jimenez and a team of detector experts at the National Institute of Standards and Technology (NIST) are working together to make x-ray movies of a molecular drama. The team at NIST built a microcalorimeter x-ray spectrometer capable of performing time-resolved spectroscopy; in other words: a camera to film Ralph and a team at NIST break a molecular bond in CO-heme (Carbon-monoxy- molecules. They use this iron protoporphyrin IX) with a laser. They then use x-rays to watch how the electron camera to learn how mol- configurations and bond lengths change, with a time resolution of < 6 picoseconds. The combined frames form a movie of sorts, depicting the real-life drama of ecules break their bonds— everyday molecules. Credit: Jimenez Group and Brad Baxley, JILA do the electrons rearrange, do the other atoms quake? The microcalorimeter spectrometer is not the only tool that can film molecules, but it is the smallest.