Syllabus: GS3/ Science and Technology
Context
- Recent advances in theoretical physics and experimental spectroscopy have enabled scientists to test the foundations of quantum mechanics and quantum electrodynamics (QED) using the hydrogen molecule (H₂).
Background
- The hydrogen molecule (H₂), has long been used to test the accuracy of fundamental physical laws.
- With advances in experimental techniques, scientists can now measure the energy gaps between different molecular states with an accuracy of one part in 100 billion.
- At this level, even very small theoretical inaccuracies become detectable, making it necessary to refine existing models.
| What is hydrogen? – Hydrogen is the chemical element with the symbol H and atomic number 1. – Hydrogen is the lightest element and the most abundant chemical substance in the universe, constituting roughly 75% of all normal matter. – It is colorless, odorless, tasteless, non-toxic, and highly combustible gas. |
Significance of hydrogen molecule in testing
- Stable molecule: H₂ consists of two protons and two electrons, making it the simplest system where molecular bonding occurs.
- It allows testing whether fundamental theories developed for atoms extend accurately to molecules.
- Benchmark system: Because of its simplicity, any deviation between theory and experiment in H₂ can signal gaps in fundamental physics.
Physical effects incorporated in experiment
- Electron–electron correlation: The calculation accurately captured how the two electrons influence each other’s motion. Ignoring this interaction leads to incorrect energy predictions.
- Electron–nucleus coupled motion: The nuclei (protons) were allowed to move slightly in response to electron motion. This “recoil effect,” becomes significant when measurements are made with very high accuracy.
- Relativistic corrections: Since electrons move at very high speeds, effects predicted by Einstein’s theory of special relativity were included to refine energy calculations.
- Quantum Electrodynamics (QED) effects: Tiny corrections arising from the interaction of charged particles with electromagnetic fields were accounted for in the experiment. These effects are usually negligible but are now experimentally measurable.
| Key principles associated with the experiment – Spectroscopy: It is a technique used to measure energy level differences in atoms and molecules by analysing absorbed or emitted light. – Quantum Electrodynamics (QED): A part of quantum field theory describing how charged particles interact with electromagnetic fields. a. It predicts tiny corrections to energy levels beyond basic quantum mechanics. |
Source: TH
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