Spontaneous and Stimulated Emission of Radiation by Professor G Srinivasan

Explore the fascinating world of quantum radiation in this comprehensive lecture on spontaneous and stimulated emission by Professor G Srinivasan. Delve into Einstein's groundbreaking 1917 paper and his profound insights that led to the development of quantum theory. Examine key concepts such as Einstein coefficients, absorption and emission processes, and inverted population. Investigate two-state systems in quantum mechanics, including Zeeman and hyperfine splitting of energy levels. Discover the intricacies of the hydrogen atom's hyperfine structure and the ammonia molecule's properties. Learn about masers, including ammonia and hydrogen variants, and their significance in astrophysics. Gain insights into celestial masers and their role in understanding the universe. This lecture, part of the "Summer course 2018 - A Random walk in astro-physics" series, provides a deep dive into the physics underlying various astronomical phenomena, from interstellar hydrogen clouds to active galactic nuclei.

Summer course 2018 - A Random walk in astro-physics
Spontaneous and Stimulated Emission of Radiation Lecture - 02
Quantum theory of radiation
The opening sentence of Einstein's 1917 paper:
But Einstein wanted his quantum theory to give Planck's Law!
Einstein's profound insight in 1917:
Definition of the Einstein coefficients in Quantum Mechanics
Spontaneous Emission
Stimulated emission
Absorption and Emission coefficients in terms of the Einstein Coefficients.
Absorption coefficient alpha
It is useful to regard stimulated emission as negative absorption .
Inverted population
Two-state systems in Quantum Mechanics
Zeeman splitting of energy levels
Hyperfine splitting of energy levels
Fine structure of energy levels of electron in atoms
Hyperfine Splitting
Hyperfine splitting of ground state of hydrogen atom Enrico Fermi, 1930
After some standard steps,
Radial wave function of Is electron in a hydrogen atom
Hyperfine splitting of n=1 level of hydrogen atom
Ammonia molecule
Electric dipole moment of Ammonia molecule
Two-state systems in Quantum Mechanics
Maser
Ammonia Maser
Hydrogen Maser
The Nobel Prize in Physics 1964
3-level laser
Celestial Masers
Next Lecture - The Interstellar Medium
Q&A