Measurement Of The Movement Of Electrons. Find Out How They Did It And More!
Electrons take only attoseconds to move and the process is so fast for an atom to jump from one place to another that it is very difficult to measure. Thanks to the novel technique developed by scientists it is now possible to measure time delays with zeptoseconds (a trillionth of a billionth of a second).
This could happen because of the Australian Attosecond Science Facility and the Centre for Quantum Dynamics of Griffith University in Brisbane, Australia.
This novel interferometric technique can be used by scientists to measure the time delay between extreme ultraviolet light pulses emitted by two isotopes of hydrogen molecules – H2 and D2 – interacting with intense infrared laser pulses which is less than three attoseconds.
According to scientists, the cause of the delay is the slightly different motions of the lighter and heavier nuclei.
Methods to Measure
- High harmonic generation (HHG): it is a technique where molecules are revealed to strong laser pulses to create the actual light waves.
- The Extreme ultraviolet (XUV) radiation is discharged right when an ion is connected again with an electron extracted from a molecule by a laser field. After that, the electron is accelerated by the same field.
- Each and every individual atom and molecule releases HHG radiation in a different manner and then the exact same process of the electron wave functions applied in this procedure influence the XUV HHG radiation’s intensity and phase.
- An ordinary grating spectrometer can measure the spectrum intensity of HHG easily but measuring the HHG phase is more tedious.
- The phase includes the most crucial data regarding the timing of extreme emission processes.
- The two copies of the wave with strictly regulated delays are elicited to overlap (or interfere) with one another in a method known as interferometry to measure this phase.
- Relying on their latency and relative phase difference, they can impede constructively or destructively.
- The interferometer is a device utilized to take this measure and it is very challenging to establish and maintain a stable and predictable, and finely tunable delay between two XUV pulses in an interferometer for XUV pulses.
- This problem was solved by taking advantage of the Gouy phase phenomenon.
- Molecular hydrogen is the simplest molecule in nature and it comes in two distinct isotopes hence scientists employed it in their studies.
- The only nucleus mass difference between light (H2) and heavy (D2) hydrogen isotopes is between protons in H2 and deuterons in D2. The electronic composition and energies and everything else are the same.
- The larger mass of the nuclei in D2 makes them move slightly slower than those in H2, this is because the nuclear and electronic motions in molecules are coupled. The nuclear motion affects the dynamics of the electron wavefunctions during the HHG process resulting in a small phase shift ΔφH2-D2 between the two isotopes.
- This phase shift is equivalent to a time delay Δt = ΔφH2-D2 /ω where ω is the frequency of the XUV wave.
- This emission time delay for all the harmonics observed in the HHG spectrum was discovered by Griffith scientists, it was nearly constant and slightly below three attoseconds.
More Advanced Methods
- As time passed scientists started using the most developed theoretical methods to comprehensively model the HHG process in the two isotopes of molecular hydrogen.
- Which also encompasses all degrees of freedom for nuclear and electronic motion at varying levels of approximation.
- The scientists were confident that their simulation was accurate and captured the exact critical characteristics of the underlying physical process because it precisely relayed the experimental results.
- By varying the model’s parameters and levels of approximation, one can determine the relative significance of different effects.
Professor Igor Litvinyuk, Griffith University, School of Environment & Science, Nathan, Australia, said,
“Because hydrogen is the simplest molecule in nature and it can be modeled theoretically with high accuracy, it was used in these proof-of-principle experiments for benchmarking and validation of the method.” “In the future, this technique can measure ultrafast dynamics of various light-induced processes in atoms and molecules with unprecedented time resolution.”
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