The document discusses several topics related to atomic structure and quantum mechanics. It begins by discussing quantization and how the work of Planck, Einstein, and others led to the concept of photons and quantized energy levels in atoms. It then discusses the photoelectric effect demonstrated by Einstein that helped establish the particle nature of light. Finally, it discusses population inversion in lasers and how certain materials like argon can be excited to a state that allows for stimulated emission of coherent light.

1. Rob’s favorite story!!!
• 6.1 Electromagnetic Radiation
• 6.2 Quantization: Planck, Einstein, Energy,
and Photons.
• 6.3 Atomic Line Spectra and Neils bohr

2. Military laser information
• Military US Navy info on lasers
• An index of Technologies that profit from the
unique properties of Lasers LASER SAFETY
• Some representative Laser types
• The Argon Ion laser
• I. What is a laser? a) A Brief History of the Laser II.
How does a laser work? a) Atomic structure,
radiation and emission b) Population inversion c)
Argon as an excitation medium

3. Argon as an excitation medium
• The neutral argon atom is pumped to the 4p energy level -the origin
of the lasing transition- by two collisions with electrons. The first
ionizes the atom and the second excites it from the ground state E1
either directly to the 4p level (E3) or to E4, from which it cascades
almost immediately to 4p. The 4p ions eventually decay to 4s (E2),
either spontaneously or when stimulated to do so by a photon of
appropriate energy.
• The wavelength of the photon depends on the specific energy
levels involved, but will be between 400 and 600 nm. The ion
decays spontaneously from 4s to the ground state emitting an
ultraviolet photon, about 74 nm.

4. Population inversion of energy
http://itl.chem.ufl.edu/4411L_f00/i2_lif/ar_laser.htm
l

5. After J. J. thompson, and Rutherford
and Milikan oil drop experiment
• Cathode rays and gold foil experiment
• J.J. Thompson- discovered the charge to mass
ratio of the electron
• Milikan –Oil drop experiment discovered the
electron charge-by which figured out the mass
• Rutherford and Gieger- said there is a dense
positve nuclear charge

6. Strawberry model of atom

7. Nobel - Ernest Rutherford -
http://www2.slac.stanford.edu/vvc/no
bel/rutherford.html

8. FOR MANY YEARS AFTER.

9. Now- Matter waves

10. The cloud model
• The cloud model represents a sort of history of where
the electron has probably been and where it is likely to
be going.
• The red dot in the middle represents the nucleus while
the red dot around the outside represents an instance
of the electron.
• Imagine, as the electron moves it leaves a trace of
where it was.

11. .• This collection of traces quickly begins to resemble a
cloud. The probable locations of the electron predicted by
Schrödinger's equation happen to coincide with the locations
specified in Bohr's model.

12. Erwin Rudolf Josef Alexander
Schrödinger
• (German: English: ; 12 August 1887 –
• 4 January 1961) was an Austrian physicist and
theoretical biologist who was one of the
fathers of quantum mechanics, and is famed
for a number of important contributions to
physics, especially the Schrödinger equation,
for which he received the Nobel Prize in
Physics in 1933.

13. http://hyperphysics.phy-
astr.gsu.edu/hbase/hyde.html

14. What is quantum mechanics?
Used to predict the shape of the
electron cloud

15. The Postulates of Quantum
Mechanics.
• Lecture 1
– The Postulates of Quantum Mechanics.
– Another source of QM Postulates.
• Lecture 2
– Plots of some Legendre Polynomials on the interval x = [-1,1]
– Pictures of spherical harmonics (absolute magnitudes)
– Lecture 2 Highlights
• Lecture 3
– Lecture 3 Highlights
– Spherical Harmonic |Y2
m|2
• Lecture 4
– Lecture 4 Highlights
– H-Atom radial wavefunctions
– H-Atom Orbitals
– Notes on series solutions to differential equations

16. spherical harmonics (absolute magnitudes)
• The view of the atom is mathematical and
philisophical??
• It is jus over the last 25 years do we now have
very powerful instruments to say that
predictions made were pretty accurate!

17. Desription of matter waves
• Common experience tells us that the behavior
of waves is much different than the behavior
of particles.
• Wave phenomema has many common
examples, but all waves share some common
features. Waves have a frequency, a
wavelength, a wave velocity, and an
amplitude, which may be examined in the
following figure:

18. Einstein showed wave particle duality
of matter and light
• The photoelectric effect- metals have a work
function

19. .

20. First describe light

21. wavelength l and the frequency n
For a given type of wave in a given medium, the wavelength l and the
frequency n can be related to the speed of propagation of the
wave(wave velocity) as follows:
• l n = c
•
• For Light (electromagnetic waves) travelling in a vacuum, this speed
of propagation is mighty quick:
• 2.99792 x 108 m/s.
•
Light is just one portion (one range of frequencies) of the EM
spectrum, which spans vastly diverse types of radiation:

23. • A device that separates light by its frequency
is said to 'disperse' the light. Prisms and
raindrops disperse light by refraction, gratings
and holograms by diffraction.

24. P
A prism: device that separates light by its frequency is said to
'disperse' the light. Prisms and raindrops disperse light by
refraction, gratings and holograms by diffraction.

25. Pic of cd

26. 6.2 Quantization: Planck, Einstein,
Energy, and Photons.
• 6.2 Quantization: Planck, Einstein, Energy,
and Photons.
• 3 things lead to this!!!
• The uv catastrophy
• The photoelectron effect
• Slit experiment-davisson and gilmer

27. 6.2 Quantization: Planck, Einstein,
Energy, and Photons.
• The uv catastrophy

28. 6.2 Quantization: Planck, Einstein,
Energy, and Photons.
• Slit experiment-davisson and gilmer

29. 6.2 Quantization: Planck, Einstein,
Energy, and Photons.
• Einstein showed wave particle duality
of matter and light
• By the The photoelectron effect

30. • When ultraviolet light falls on certain metals,
electrons are emitted. This phenomenon in
which certain metals emit electrons when
exposed to light of suitable frequency, is called
PHOTO ELECTRIC EFFECT.
In short, ejection of electrons by means of
light is called 'photo electric effect'

31. • Electrons ejected from a sodium metal surface
were measured as an electric current. Finding
the opposing voltage it took to stop all the
electrons gave a measure of the maximum
kinetic energy of the electrons in electron
volts

32. What Einstein saw . . ..
• The number of photo electrons depends
upon:
1. The nature of material
2. The frequency of incident radiation
3. The intensity of incident radiation
4. Potential difference b/w the electrons

33. Work Function
• Minimum amount of energy which is necessary
to start photo electric emission is called Work
Function. If the amount of energy of incident
radiation is less than the work function of metal,
no photo electrons are emitted. It is denoted by .
• Work function of a material is given by .
It is a property of material. Different materials
have different values of work function. Generally,
elements with low I.P values have low work
function such as Li, Na, K, Rb, and Cs.

34. Work Function

35. Frequency determines energy!!
• Heinrich Rudolf Hertz (February 22, 1857 –
January 1, 1894) was a German physicist who
clarified and expanded the electromagnetic
theory of light that had been put forth by
Maxwell. He was the first to satisfactorily
demonstrate the existence of electromagnetic
waves by building an apparatus to produce
and detect radio waves

36. Unit of energy
Hertz = Hz = 1/s = s-
Electon volt=
Joules
Frequency
Nanometers
wavenumbers

37. propagation of electric action
• Hertz published his work in a book titled:
Electric waves: being researches on the
propagation of electric action with finite
velocity through space.[3]

38. Through experimentation, he proved that transverse
free space electromagnetic waves can travel over some
distance

39. wave vector-theory of wave packet

40. THRESHOLD FREQUENCY
• Threshold frequency is defined as the
minimum frequency of incident light which
can cause photo electric emission i.e. this
frequency is just able to eject electrons with
out giving them additional energy.
It is denoted by

41. Must understand this principle
1. the intensity of light will not increase the
number of electrons eject
2. The frequency of light determines the
number when electrons will be ejected
3. The energy of light is determined by :
• C = l u= 3.00 x 108 m/s
l = lamda=wavelength
u= upsilon= frequency

42. Light is like a acordian

43. To the text
• 6.11 an energy of 3.3 x 10-19 J/atom is
required to cause a cesium atom on a metal
surface to lose an electron. Calculate the
longest possible wavelength of light that can
ionize a cesium atom.
• In what region of the spectrum does this
radiation lie?

44. On MCAT
• 6.11 You are an engineer designing a switch
that works by the photoelectric effect. The
metal you wish to use in your device requires
6.7 x 10-19 J/atom to remove an electron.
• Will the switch work if the light falling on the
metal has a wavelength of 540 nm or greater?
• Why or why not?

45. Your time line

47. • Electron Transitions
• The Bohr model for an electron transition in
hydrogen between quantized energy levels
with different quantum numbers n yields a
photon by emission with quantum energy:
This is often expressed in terms of the inverse
wavelength or "wave number" as follows: