1. ASTR 1101-001 Spring 2008 Joel E. Tohline, Alumni Professor 247 Nicholson Hall [Slides from Lecture20]

12. Light and Atomic Transitions Electron orbital transitions upward –Absorption of a photon (of appropriate energy, frequency, wavelength) –Collisional excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Ionization possible

13. Wavelength and Frequency Wavelength = Frequency = c = speed of light = c

14. Light and Atomic Transitions Electron orbital transitions downward –Spontaneous Emission of a photon (of appropriate energy, frequency, wavelength) –Collisional de-excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Recombination is opposite of ionization –Stimulated emission also possible

15. Light and Atomic Transitions Electron orbital transitions upward –Absorption of a photon (of appropriate energy, frequency, wavelength) –Collisional excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Ionization possible

16. Light and Atomic Transitions Electron orbital transitions downward –Spontaneous Emission of a photon (of appropriate energy, frequency, wavelength) –Collisional de-excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Recombination is opposite of ionization –Stimulated emission also possible

17. Light and Atomic Transitions Electron orbital transitions upward –Absorption of a photon (of appropriate energy, frequency, wavelength) –Collisional excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Ionization possible

18. Light and Atomic Transitions Electron orbital transitions downward –Spontaneous Emission of a photon (of appropriate energy, frequency, wavelength) –Collisional de-excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Recombination is opposite of ionization –Stimulated emission also possible

19. Light and Atomic Transitions Electron orbital transitions downward –Spontaneous Emission of a photon (of appropriate energy, frequency, wavelength) –Collisional de-excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Recombination is opposite of ionization –Stimulated emission also possible

20. Light and Atomic Transitions Electron orbital transitions upward –Absorption of a photon (of appropriate energy, frequency, wavelength) –Collisional excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Ionization possible

21. Light and Atomic Transitions Electron orbital transitions downward –Spontaneous Emission of a photon (of appropriate energy, frequency, wavelength) –Collisional de-excitation ( rate and effectiveness of collisions depends on density and temperature of gas ) –Recombination is opposite of ionization –Stimulated emission also possible

22. Kirchhoff’s Laws Hot dense gas produces a continuous spectrum ( a complete rainbow of colors ) Hot transparent gas produces an emission line spectrum Cool transparent gas in front of a source of continuous spectrum produces an absorption line spectrum.

23. Kirchhoff’s Laws Hot dense gas produces a continuous spectrum ( a complete rainbow of colors ) Hot transparent gas produces an emission line spectrum Cool transparent gas in front of a source of continuous spectrum produces an absorption line spectrum.

25. Kirchhoff’s Laws Hot dense gas produces a continuous spectrum ( a complete rainbow of colors ) Hot transparent gas produces an emission line spectrum Cool transparent gas in front of a source of continuous spectrum produces an absorption line spectrum.

29. Kirchhoff’s Laws Hot dense gas produces a continuous spectrum ( a complete rainbow of colors ) Hot transparent gas produces an emission line spectrum Cool transparent gas in front of a source of continuous spectrum produces an absorption line spectrum.