Just as in the past the photographer Muybridge needed the right equipment to capture the perfect picture of the gait of a galloping horse, so physicists needed a superfast camera to accurately observe the motion of electrons. As we know that when the object moves very fast then the image(s) of the object become blurred. However, a faster strobe light can illuminate the object for less than a second. And we can take images that remain stable over time. To observe the movement of electrons within atoms and molecules we need an intense beam of light. This time in the year 2023, it has been announced that the Nobel Prize for Physics will be given to Pierre Agostini, Ferenc Krausz and Anne L'Huillier and somewhere their discovery can be used in making a superfast camera. And it may be possible to take pictures of all the phenomena involving the behavior and rapid dynamics of electrons within atoms.
The observation of rapid mobility was initiated by Egyptian-American scientist Ahmed Hassan Zewail (February 26, 1946 – August 2, 2016). He invented the first strobe light which glows for a time period of only tens and hundreds of femtoseconds (one millionth of a billionth of a second). Zewell observed in his early studies that the chemical reaction between hydrogen atoms and carbon dioxide: H + CO2 → CO + OH involves an intermediate state in which HOCO is formed and this lasts for up to 1000 femtoseconds before disintegrating into CO + OH. Remains. He was awarded the Nobel Prize in the year 1999 for his study of chemical reactions occurring in femtoseconds and the establishment of femtochemistry. This made it clear that we can obtain a pulse of only femtoseconds using an excellent strobe effect, which is helpful in understanding the chemical reactions taking place between molecules. Whereas we need pulses a thousand times smaller than a femtosecond to accurately picture the chemical reactions inside atoms and molecules. The wavelength of visible light is between 400 nanometers (violet light) to 700 nanometers (red light). It takes between 1.3 and 2.3 femtoseconds for a single wave to travel from its peak to its trough and then back to its peak. But even the temporary vibration of this time period is not suitable to depict the rapid mobility of electrons and their position inside the atom.
Thinking an innovation!
Can we measure small units that cannot be represented on a normal scale?
For example, suppose we have two jars measuring only 5-litre and 3-litre and using both of them we can easily measure one liter of water. Let us understand it step by step.
1. Fill a 3-litre container with water.
2. Pour water from the 3-litre can into the 5-litre can.
3. Fill the 3-litre canister again with water.
4. Pour water from the 3-litre can into the 5-litre can until it is completely filled.
We still have 1 liter of water left in the 3 liter can. And thus the purpose of measuring one liter of water was accomplished without the need for any one liter measuring jar.
With similar thinking, Anne L'Huillier and her team presented a solution through the present discovery.
We know that light also behaves like a wave. When two waves of light meet each other, some new results are seen. If both the waves have the same wavelength and the peak of one is in phase with the peak of the other then in that case they add up and the amplitude of the resultant wave increases. However, if the wavelengths are the same and the peak of one exactly matches the trough of the other then they cancel out. And if two waves of different wavelengths meet, they superimpose on each other and form a new hybrid wave. In 1987, Anne L'Huillier and her colleagues made a very interesting observation: just as overtones can be produced from a plucked string of a bowed "guitar", atoms of some noble gases can be produced by means of a powerful infrared laser. By excitation, ultraviolet light can be generated, whose oscillation is many times higher than that of the primary laser.
Anne L'Huillier and other researchers found that the primary laser briefly stripped an electron from the gas atom. however! In a short time the electron then returned to the atom, representing a wave. The resulting waves during this phenomenon produce harmonic overtones. The frequency of these overtones is not just two or three times but up to thirty times higher. In conclusion, the oscillation of these overtones was found to be much larger than the oscillation of the incident light. After much intensive investigation these scientists succeeded in accurately calculating the frequencies of the resulting overtones. In its second phase, he did the work of mapping the resulting frequencies and a new hybrid wave was added to it.
Just as in an orchestra, a new symphony can be created by combining different pieces of music from different instruments. Similarly, L'Huillier and his team showed that by combining light waves of different wavelengths we can obtain light pulses of desired duration.
In the 1990s, after several years of research, L'Huillier and his colleagues demonstrated that waves of different wavelengths could be combined with their peaks in phase to produce interference. This way we can generate very short light pulses. This new hybrid wave gave rise to a new branch of physics depicting isotropic interference, which we also know as attosecond physics.
In the year 2001, scientist Agostini and his team combined all these fractionated pulses in such a way that light waves could be pulsed continuously with a time interval of only 250 attoseconds. Meanwhile, another prominent scientist, Ferenc Krausz and his team had succeeded in detecting a single light pulse lasting 650 attoseconds. On the other hand, in the year 2001 itself, the team of scientist Agostini observed a light pulse which had a duration of only 250 attoseconds. In the sequence of this research, in the year 2003, L'Huillier's research group succeeded in obtaining a light pulse of 170 attosecond duration and in the year 2008, scientist Ferenc Krause succeeded in obtaining a pulse of 80-attosecond duration. Recently, scientist Jacob Woerner and his research colleagues have succeeded in obtaining a pulse with a time duration of 43 attoseconds.
