1. Physics 1202: Lecture 35 Today’s Agenda
Announcements:
Extra credits
Final-like problems
Team in class
Teams 6, 7 & 8
HW 10 due Friday next week
Atomic Physics 1

2. Atomic Physics

3. Bohr’s quantum model of atomv
1. Electron moves in circular orbits.
2. Only certain electron orbits are stable.
3. Radiation is emitted by atom when electron
jumps from a more energetic orbit to a low
energy orbit.
4. The size of the allowed electron orbits is
determined by quantization of electron
angular momentum

4. Bohr’s quantum model of atom
Orbits of electron in Bohr’s
model of hydrogen atom.
Frequency of the emitted photon
Dependence of the wave length
An energy level diagram for hydrogen atom

5. Quantum numbers Numbers used to describe a quantum state
En = - E0 n-2 with E0 = 13.6 eV
n : principal quantum number
Angular momentum L
Classically, any value
Quantum mechanically
Quantized (Bohr model):
Discrete values
where l = 0,1,2,… and l < n

6. Quantum numbers Hydrogen ground state with n=1 - l < m < + l
l = 0,1,2,… and l < n implies l = 0 only (called s)
n = 2 implies l = 0 or 1 (called s and p)
n = 3 implies l = 0, 1, or 2 (called s, p, and d)
Quantization axis
Magnetic field along z
Projection on z
- l < m < + l

7. Electron spin Electron has an intrinsic angular momentum: spin
with ms = ± ½

8. Pauli exclusion principle
Wolfgang Pauli (1925): Nobel 1945
No electron can be in the same quantum state
No more than 2 electrons in an orbital
For a given n, l, m with ms = ± ½
Explains the periodic table
Electronic configuration
Shell structure of atoms

9. Periodic table Atomic structure and chemical properties
Pauli principle: atomic shell model

10. X-ray emission from atoms
X-ray tube
Discovered by Wilheim Röntgen (1895)
Accelerated electrons hit targets
Large potentials kV to MV

11. X-ray emission from atoms
Bremsstrahlung
Continuous x-ray
Electron loosing energy
Minimal l
When all initial K is lost

12. X-ray emission from atoms
K, L, etc. shells and x-ray emission
Fast electron kick inner electron out
Higher electron falls in and fill the “hole”
X-ray emitted

13. X-ray emission from atoms
Each element has a specific spectra
lmin