PLASMA SPECTROSCOPY

Plasma spectroscopy is an essential investigation tool in astrophysics, physics laboratory, and applied physics. Plasma spectroscopy is fundamental in, e.g., environmental analysis, nuclear fusion experiments, analysis of the atmosphere of stars and exoplanets, and supernovae explosion. This course deals with fundamental concepts of spectroscopy of both laboratory and astrophysical plasmas, including the neutral gas limit. After a review of fundamental concepts of atomic and molecular physics and of the relevant interactions, plasma equilibrium conditions and corresponding theoretical description are discussed. The formation of spectra in homogeneous and inhomogeneous plasmas is then treated, together with an introduction to the theory of stellar atmospheres. In the final part, the principles of diagnostics applications are presented.

Knowledge and understanding:

The course provides the student with the necessary knowledge and understanding on how information about the plasma is inferred from the analysis of the radiation emitted. The theory and practical methods introduced in this course are common to both laboratory and astrophysical plasmas.

Applying knowledge and understanding:

The student can acquire the capability of understanding the scientific literature in which plasma spectroscopy is involved and the necessary knowledge for working with plasma spectroscopy in laboratory and astrophysical research, as well as in applied physics contexts.

Making judgments:

Students have the opportunity to increase their competence level in making judgments on the validity of scientific results based on plasma spectroscopy, as well as on the possibility of solving research and applied physics problems using spectroscopy.

Communication skills:

The course gives the student the possibility of acquiring specific competences for a correct and effective communication of topics where plasma spectroscopy is involved.

Learning skills:

The student can acquire adequate cognitive methods for a continuous update on scientific topics involving plasma spectroscopy.

The main concepts are taught in front lectures, which include practical examples. Learning effectiveness is monitored through written exercises and intermediate tests.

Should the circumstances require online or blended teaching, appropriate modifications to what is hereby stated may be introduced, in order to achieve the main objectives of the course. Exams may take place online, depending on circumstances.

1. The hydrogen spectrum

Energy levels; wave functions; selection rules; spectral series; Hydrogen-like ions; fine structure; spin-orbit interaction.

Ref: [1], [5]

2. Spectra of multi electron atoms

Central field approximation; parity of states; systematics of electron states in a central field; spin-orbit interaction; spectral terms; LS coupling; jj coupling; examples

Ref: [1], [5]

3. Molecular spectra

Born-Oppnheimer approximation; electron binding of nuclei; pure rotation spectra; rotation-vibration spectra; electronic-rotational-vibrational spectra.

Ref. [4]

4. Radiative processes

Line radiation: radiative transition probability; dipole radiation; selection rules; oscillator strength; transition-line strength; multiplets.

Continuum radiation; recombination radiation and photoionisation; Bremsstrahlung; negative ion and molecular continua; rate coefficient for radiative recombination.

Ref. [1], [2]

5. Collisional processes

Collisional excitation and de-excitation by electron impacts; electron impact ionization and three-body recombination; dielectric recombination and auto-ionisation; charge exchange processes; ion and atom impact excitation and ionization.

Ref. [2]

6. Kinetics of the population of atomic levels

Thermodynamic equilibrium; local thermodynamic equilibrium; non-local thermodynamic equilibrium; coronal equilibrium; collisional-radiative models.

Ref. [1], [2], [3], [4], [6]

7. Line broadening

Profile functions; natural broadening; Doppler broadening; pressure broadening by neutral particles; Stark broadening; plasma dynamics effects; effects of magnetic and electric fields; stellar rotation.

Ref. [2], [3], [6], [4]

8. Radiative transfer

Radiation field; photon distribution function; emission; absorption; radiative transfer equation optical depth and source function; radiative equilibrium; diffusion approximation; formation of spectral lines; models of stellar atmospheres.

Ref. [3], [4], [6]

9. Diagnostic applications

Measurements of particle densities; temperature measurements; measurements of electron density; electric and magnetic field measurements; measurements of stellar surface gravity; measurements of chemical abundances in the stellar atmosphere.

Ref. [2], [8]

Main bibliography:

[1] Lanzafame A. C., Plasma Spectroscopy Course Notes, 2021

[2] Kunze H-J, Introduction to Plasma Spectroscopy, Springer, 2009

[3] Rutten R.J., “Radiative Transfer in stellar atmospheres”, https://robrutten.nl/rrweb/rjr-pubs/2003rtsa.book.....R.pdf, 2003

[4] Rybicki G. B., Lightman A. P., Radiative Processes in Astrophysics, Wiley-VCH, 2004

Extended bibliography:

[5] Sobelman I. I., Atomic Spectra and Radiative Transition, Springer-Verlagh, 1992

[6] Mihalas D., Stellar Atmospheres, Freeman & C., 1978

[7] Sobelman I. I., Vainshtein L. A., Yukov E. A., Excitation of Atoms and Broadening of Spectral Lines, Springer-Verlag, 1981

[8] Gray D.F., The observation and analysis of stellar spectra, Cambridge Astrophysics Series, 2005