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Getting a measure of atoms

We are not new to measuring things. From the simple ruler we start using as kids, to the fine balance that measures weight to a hundredth of a gram of gold, our lives are driven by instruments that measure stuff. However, not many of us know that many physicists need to measure quantities in a world that we can't even see: the atom. Vasant Natarajan, Professor of Physics, Indian Institute of Science, is one among them.

To get a 'measure' of what Professor Natarajan does, we have to get a sense of how small his ‘world’ is. If a tiny droplet of water is bubbling with billions and billions of restless water molecules, imagine how small a single molecule could be! And, each water molecule is made of three atoms: two hydrogens and one oxygen. These atoms are so small that about a lakh of them can be packed on the tip of a human hair. The atom is the world for Professor Natarajan.

The atomic world is different. This world follows a set of physical laws that are different from the laws that are followed in the world we see and experience. Ambiguity is built into that world: for example, finding the exact position of an electron is not just difficult, but impossible. It doesn't matter how good our instrument is: there are laws of nature that forbid us from knowing such simple facts. But, we can't blame nature when we don't know the 'position' of a pen, because, the effects of such laws are too small to be observed in our world! However, they do make Professor Natarajan's work extremely challenging and fascinating.

Since his PhD days at the Massachusetts Institute of Technology, Prof Vasant Natarajan has immersed himself in the atomic world. As a PhD student, he accurately measured the masses of many atoms (like hydrogen, nitrogen, neon, etc), and they continue to be one of the most precise measurements reported till date. After a period of research at the celebrated AT&T Bell labs, he joined the Physics department of the Indian Institute of Science (IISc), and currently heads the laboratory for Atomic and Optical Physics. In the lab at IISc, he uses lasers to cool atoms almost to the lowest attainable temperature, -273 C, and makes precision measurements at the atomic level. His lab is one of the coolest places in the world, in more ways than one!

The techniques developed by Professor Natarajan to peek into the world of atoms have benefited other branches of physics too. For example, cooling atoms to such low temperatures allows for extremely precise measurements of their properties, such as what is known as a permanent electric dipole moment (EDM). The existence of an EDM would provide a huge boost to certain theories of fundamental physics, and a prize for such an experiment has been announced by Nobel Laureate Norman Ramsey (Natarajan’s advisor’s advisor). Prof. Natarajan's research group has firmly established its intention to pursue this prize, with laser cooling assisted experiments on atoms of an element called ytterbium well under way.

While acknowledging the excellent work of his research team of students and staff, Prof. Natarajan reveals what drives him in his scientific research. “My main motivation to carry research in atomic physics is to make a lasting contribution, especially one that advances our knowledge”, he says. The results that continue to be reported from his laboratory are indeed a reflection of this intent.

Prof Vasant Natarajan is with the Department of Physics, Indian Institute of Science, Bengaluru. He can be reached at 080 – 2293 3341, 080 – 2360 2237, 080 – 2293 2717.

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physics