27202 - Chemical and Physical Processes of Interstellar Medium

Learning outcomes

At the end of the Course Student is expected to be able to discuss the effects of the main physical-chemical processes taking place in the different astrophysical environments: absorption and emission of light from atoms, molecules, ions and radicals, collisional and radiative excitations, pressure and temperature bandshape broadening, maser generation from optical and collisional pumping, formation and desctruction of molecules in the gas phase, formation of molecules on the grain surface.

Course contents

 

1)      Many-electron atoms: fine structure of electronic levels of atoms and ions in the ISM (He, He+, Na, Mg, C, OIII, NII, Si). 

2)      Molecules: vibro-rotational structure of  electronic levels. Spin effect and nuclear statistics. Fine and hyperfine structure. Molecular symmetry. The Deuterium fractionation.

3)      Radiation-matter interaction: from the Fermi's golden rule to the selection rules for rotational, vibrational and electronic transitions. Electric dipole, magnetic dipole and electric quadrupole mechanisms. Competitions between collisional and radiative processes.

4)      Spectral bandshapes: Doppler and pressure broadening and contribution from microturbolence.

5)       Basic aspects of chemical kinetics: collisional theory and transitino state theory. Applications of statistical mechanics.

6)      ISM Molecular formation processes. Reactions in the gas phase: neutral-neutral, ion-molecule, radiative association.  Molecular destruction processes: Photodissociation 

 7)      Molecule formation on surfaces. The Dust grains: structure, adsorption processes (thermodynamics and statistical aspects), surface atoms mobility: quantum-mechanics (tunnelling) and statistical-thermodynamics (diffusion); desorption  and  energy redistribution  processes

8) Molecules as probes of the ISM and their spectroscopic observation: H2, C2, CO, OH (maser),CH3, NH3, H2CO (formaldheide),  cyanopolynes (HC2n+1N), PAH's (Polycyclic Aromatic Hydrocarbons). Temperature and density diagnostics.

 

 

Readings/Bibliography

Lecture notes

Books: The Physics and Chemistry of the Interstellar Medium, A.G.G.M. Tielens, 2005, Cambridge University Press.

            Interpreting astronomical spectra, D. Emerson  John Wiley and Son, 1997.

Teaching methods

The teaching method consists in the close fullfilment of an ordered time correlation of the presentation of a concept (or of its application) with the video projection of the equations (or plots and figures) relevant for its discussion so that student's attention can focus  time to time on that aspect of the treated subject.

Whenever appropriate, students are stimulated to anticipate their own point of view on the possible outcomes of a treatment

Assessment methods

Oral exam

Teaching tools

Blackboard and video projector

Office hours

See the website of Maria Grazia Giorgini