Chapter 29 Tutorial (continued).




Putting it All Together

In general the Energy of a diatomic molecule is a combination of both the vibrational and rotational levels and is given by
E(n,L) = (n+1/2)hf + L(L+1)hbar2/2I
and transitions are subject to the rules: Dn=|1|, DL =|1|.


Allowed Transistions
N->N+1
Radiation Absorption 		N->N-1
Radiation Emission
L->L+1 DE = hf + (L+1)hbar2/I DE = -hf + (L+1)hbar2/I
L->L-1 DE = hf - (L)hbar2/I DE = -hf - (L)hbar2/I


Interactive Activity

In the following movie the first two vibrationl levels along with the embedded rotational levels of a diatomic molecule are shown. For this molecule hf = .1 eV and hbar2/I = .01 eV, view the movie one step at a time (use buttons on the right) and answer the question for each step.
If you don't have the Quicktime plugin you will get a broken image . You can view a GIF animation version of the movie here.

If the transition is forbidden enter 'forbidden' in the box following each question, otherwise enter the energy change in eV, and then click feedback each time.

Step: 1?
Step: 2?
Step: 3?
Step: 4?
Step: 5?
Step: 6?
Step: 7?

III. Solids


When atoms form a solid their various energy levels merge together to form energy bands as shown above. If the highest band containing electrons is only partially filled the solid is a conductor. This is because the electrons can be moved by an applied electric field because there are higher energy states available to them. Conversely, if the highest band containing electrons is filled the solid is an insulator because there are no energy states available for acceleration. There is a third alternative and that is a semiconductor. One type of semiconductor is one in which the energy gap is very small. In that situation outside influences can cause electrons to jump the gap and thus putting electrons in the formally empty Conduction Band and, also,leaving room in the Valence Band for conduction.

Interactive Example

One way to find the energy gap of a semiconductor is to shine light on it with progressively shorter wavelengths until it starts to conduct electricity? If it starts conducting at 414 nm the energy gap (in eV) is...


Conversely if the energy gap is not bridged, the photon can't be absorbed and the material is transparent. Which of the following would be transparent?



© 1999 Carl Adler mailto:Carl@Image-ination.com