In this way we can keep the process going-essentially forever." But while these atoms are being used, new atoms are already on their way to replenish the BEC. In the end, ultracold atoms arrive at the heart of the experiment, where they can be used to form coherent matter waves in a BEC. In our setup, we decided to spread the cooling steps not over time, but in space: we make the atoms move while they progress through consecutive cooling steps. "In previous experiments, the gradual cooling of atoms was all done in one place. Florian Schreck, the team leader, explains what the trick was. As a result, BECs were restricted to fleeting bursts, with no way to coherently sustain them.Ī team of physicists from the University of Amsterdam has now managed to solve the difficult problem of creating a continuous Bose-Einstein Condensate. Yet the presence of light is crucial in forming the condensate: to cool a substance down to a millionth of a degree, one needs to cool down its atoms using laser light. It was clear what the problem was: BECs are very fragile, and are rapidly destroyed when light falls on them. But while the developments for optical lasers had gone very fast, the first continuous laser being produced within six months after its pulsed counterpart, for atom lasers the continuous version remained elusive for more than 25 years. In fact, ordinary, optical lasers were also made in a pulsed variant before physicists were able to create continuous lasers. For a first step towards an atom laser, this was still not bad. The lasers could produce pulses of matter waves, but after sending out such a pulse, a new BEC had to be created before the next pulse could be sent out. This opened up the possibility to build atom lasers-devices that literally output beams of matter-but these devices were only able to function for a very short time. Only at extremely low temperatures, about a millionth of a degree above absolute zero (about 273 degrees below zero on the Celsius scale), is there a chance of forming the coherent matter waves of a BEC.Ī quarter of a century ago, the first Bose-Einstein Condensates were created in physics labs. The culprit destroying the synchronicity is temperature-when a substance heats up, the constituent particles start to jiggle around, and it becomes virtually impossible to get them to behave as one. The reason: it is very difficult to get atoms to all behave as one. In everyday life, we are not at all familiar with these condensates. When this type of condensation happens for matter particles, physicists call the resulting substance a Bose-Einstein Condensate. What makes bosons so special is that they can all be in the exact same state at the exact same time, or phrased in more technical terms, they can "condense" into a coherent wave. But matter particles can also combine to form bosons-in fact, entire atoms can behave just like particles of light. The best-known example of a boson is the photon, the smallest possible quantity of light. Bosons are very different in nature: they are not hard like fermions, but soft: for example, they can move through one another without a problem. Fermions are particles like electrons and quarks-the building blocks of the matter that we are made of. Elementary particles in nature occur in two types: fermions and bosons. (3) Notes presenting a full explanation of atomic structure.The concept that underlies the atom laser is the so-called Bose-Einstein Condensate, or BEC for short. This PhET online simulation can be done in the classroom or during distance learning. All of the PhET simulations are available from their website:. PhET simulations incorporate research based, student centered activities that are fun and easy to use. The Build an Atom simulation is easy to use, interactive and gives immediate feedback when students are answering questions to check their understanding of key concepts. Students love working with the online simulations from PhET Interactive Simulations. They will also be introduced to the layout of the periodic table and how to locate elements on it. They will learn the important terms used to describe atoms such as atomic number, mass number and net charge. In this inquiry-based PhET online lab your students will investigate atomic structure and the subatomic particles that make up atoms using the Build an Atom simulation.
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