Every year on 28th February India celebrates National Science Day. Although, there is quite a bit of enthusiasm in this celebration, especially in academic environment including schools, universities and research institutes, the general public does not pay too much attention to it. Partly because symbolic days and symbolism are just that: symbols – superficial representation of something bigger. They do not encompass the complete picture, and they are too many in number.
Raman + Krishnan Effect : So, why does India celebrate National Science day on 28th February ? Well, on this day, way back in 1928, there was an experimental observation performed which turned out to be an important discovery in science. The main players in this discovery were two scientists from India: C.V. Raman and K.S. Krishnan. These men, after a long, sustained effort and with limited experimental resources, discovered a new type of secondary radiation, and the effect what is now known as Raman effect.
Stokes and anti-Stokes: The experiment that they were performing was to look at monochromatic (single colour) light scattering from molecules in a liquid. What Raman and Krishnan found was that scattered light had three components in terms of energy: the first and the dominant part of the scattered light had the same energy as the incident light, the second most dominant part of the scattered light had its energy lower than the incident light, and the third component, which was the weakest, had its energy greater than the incident light. These three components are called Rayleigh, Stokes and anti-Stokes light, respectively. The Stokes and the anti-Stokes components of the scattered light, together encompass the inelastic scattering in the process, and formally represent Raman scattering of light from molecules. What is remarkable on the part of Raman and Krishnan is that they experimentally observed these feeble, inelastic scattering components with ingenious experimental design. The story of this discovery is beautifully captured in the book The Raman and his effect by G. Venkatraman (who has also written a biography of C.V. Raman). In this book (page 46), we get a glimpse of the lab notes of K.S. Krishnan during this historical phase of experimental observation, which is reproduced below:
February 17, Friday
Prof, confirmed the polarisation of fluorescence in pentan vapour.
I am having some trouble with the left eye. Prof, has promised to
make all the observations himself for some time to come.
February 27, Monday
Religious ceremony in the house. Did not go to the Association.
February 28, Tuesday
Went to the Association only in the afternoon. Prof, was there and we
proceeded to examine the influence of the incident wavelength on the
phenomenon. Used the usual blue-violet filter coupled with uranium
glass, the range of wavelengths transmitted by the combination being
much narrower than that transmitted by the blue-violet filter alone.
On examining the track with a direct vision spectroscope, we found
to our great surprise that the modified scattering was separated from
the scattering corresponding to the incident light by a dark region
Note that it is this February 28, that we celebrate as National Science Day.
Mud + gold – I see an important lesson from this reading – that lab note books are an excellent window to the world of observations that a researcher experiences. Most of the time what is written in a lab notebook is routine stuff, but once in a while there is something important that pops out from it. The analogy is similar to digging for gold in the soil. Most of the time it is mud what you get, but once in a while you extract the precious metal. But without the effort of digging, one will never be able to extract the gold, and a lab notebook is the place where you record your efforts. So, what comes out as “success” is a small part of this greater effort. It is a tiny bit of a greater whole, and worth every bit.
Coming back to Raman and Krishnan, they published (see above) their experimental observation which caught the attention of scientific community around the world (‘western’ world to be more precise). And in 1930, Raman went on to win the Nobel prize in physics, and the rest is history. I need to emphasize that this discovery was made purely to address a quantum mechanical effect in optical regime. Specifically, the researchers were addressing an optical analog of the Compton effect, and they had no immediate applications in their mind. However, in the current age, Raman scattering spectroscopy, has bloomed into one of the most important scientific concepts, and a vital tool in science and technology, including applications in clinical bio-medicine and homeland security.
The celebration: It has been 90 years since this important discovery, and to celebrate the discovery, there was a conference at IISc, Bangalore. Some of my students and I were part of it. In there, various researchers across the world including many from India, discussed about Raman scattering and its implication over the past 90 years. One of the highlights of the conference was a lecture by Prof. Wolfgang Kiefer (given on 28th February, National Science Day), who is a legend in the community of Raman scattering. Prof. Kiefer has been working on Raman scattering for more than 50 years. Now, he is retired, but amazingly, maintains a lab in the basement of his house, in which he has set-up Raman scattering experiments (see picture above), and pursues his curiosity with child-like enthusiasm. He gave an overview of his work done with his illustrious students from the past, and beautifully blended science, humor and humanity in a single talk. To listen to him was a pleasure and inspiration, and I will remember this for ever. On a personal note, I was actually celebrating the science day without realizing it !